Circuit diagrams for galvanic batteries. Features of chargers for AA batteries. Charger Specifications

With this article we are opening a new direction for our site: testing batteries and galvanic cells (or, in simple terms, batteries).

Despite the fact that lithium-ion batteries, specific to each specific device model, are becoming increasingly popular, the market for standard general-purpose batteries is still very large - they power a lot of different products, ranging from children's toys to inexpensive cameras and professional photo flashes. The range of these elements is also large - batteries and accumulators of different types, capacities, sizes, brands, workmanship...

At first, we do not set ourselves the goal of covering all the richness of batteries - we will limit ourselves to only the most standard and widespread of them: cylindrical batteries and nickel batteries.

This article is intended to introduce you to some basic concepts regarding the batteries we are researching, as well as the testing methodology and equipment we use. However, we will discuss many theoretical and practical issues in subsequent articles devoted to specific batteries - especially since doing this using “live examples” is much more convenient and clearer.

Types of batteries and voltaic cells

Batteries with salt electrolyte

Batteries with a salt electrolyte, also known as zinc-carbon (however, unlike alkaline batteries, manufacturers usually simply do not indicate their chemistry on the packaging of salt batteries) are the cheapest chemical power sources available for sale: the cost of one battery ranges from four to five to eight to ten rubles, depending on the brand.

Such a battery is a zinc cylindrical container (which serves as both the body and the “minus” of the battery), in the center of which there is a carbon electrode (“plus”). A layer of manganese dioxide is placed around the anode, and the remaining space between it and the walls of the container is filled with a paste of ammonium chloride and zinc chloride diluted in water. The composition of this paste may vary: in low-power batteries it is dominated by ammonium chloride, and in higher-capacity batteries (usually designated by manufacturers as “Heavy Duty”) it is dominated by zinc chloride.

When a battery is in operation, the zinc from which its body is made gradually oxidizes, as a result of which holes may appear in it - then the electrolyte will leak out of the battery, which can lead to damage to the device in which it is installed. However, such problems were typical mainly for domestic batteries during the existence of the USSR, while modern ones are securely packaged in an additional outer shell and “leak” very rarely. However, you should not leave dead batteries in the device for a long time.

As mentioned above, the chemical composition of the electrolyte of salt batteries may vary slightly - the “high-power” version uses an electrolyte with a predominance of zinc chloride. However, the word “powerful” in relation to them can only be written in quotation marks - none of the varieties of salt batteries are designed for any serious load: in a flashlight they will last for a quarter of an hour, but in a camera they may not even be enough to extend the lens. The destiny of salt batteries is remote controls, watches and electronic thermometers, that is, devices whose energy consumption falls within units, at most tens of milliamps.

Alkaline batteries

The next type of battery is alkaline or manganese batteries. Some not very competent sellers and even manufacturers call them “alkaline” - this is a slightly distorted tracing paper from the English “alkaline”, that is, “lye”.

Prices for alkaline batteries vary from ten to forty to fifty rubles (however, most of their types fall into the range of up to 25 rubles, only certain models with increased power stand out), and they can be distinguished from salt ones by the inscription “Alkaline” usually present in one form or another " on the packaging (and sometimes right in the name, for example, "GP Super Alkaline" or "TDK Power Alkaline").

The negative pole of an alkaline battery consists of zinc powder - compared to the zinc body of salt cells, the use of powder allows you to increase the speed of chemical reactions, and therefore the current supplied by the battery. The positive pole is made of manganese dioxide. The main difference from salt batteries is the type of electrolyte: in alkaline batteries, potassium hydroxide is used as it.

Alkaline batteries are well suited for devices with power consumption from tens to several hundred milliamps - with a capacity of about 2...3 Ah they provide a very reasonable operating time. Unfortunately, they also have a significant disadvantage: high internal resistance. If you load a battery with a really high current, its voltage will drop significantly, and a significant part of the energy will be spent on heating the battery itself - as a result, the effective capacity of alkaline batteries is highly dependent on the load. Let's say, if when discharging with a current of 0.025 A we manage to get 3 A*h from the battery, then at a current of 0.25 A the actual capacity will drop to 2 A*h, and with a current of 1 A it will be completely below 1 A*h.

However, an alkaline battery can work for some time even under heavy loads, it’s just that this time is relatively short. For example, if a modern digital camera may not even turn on using salt batteries, then one set of alkaline batteries will be enough for half an hour of operation.

By the way, if you are forced to use alkaline batteries in your camera, buy two sets at once and periodically swap them, this will extend their life a little: if a battery discharged by a high current is allowed to “rest” for a while, it will partially restore its charge and will be able to work a little more. About five minutes.

Lithium batteries

The last widely used type of battery is lithium. They are typically rated at multiples of 3V, so most types of lithium batteries are not interchangeable with 1.5V salt and alkaline batteries. Such batteries are widely used in watches, and also, less commonly, in photographic equipment.

However, there are also 1.5 V lithium batteries made in standard AA and AAA form factors - they can be used in any equipment designed for regular salt or alkaline batteries. The main advantage of lithium batteries is their lower internal resistance compared to alkaline ones: their capacity depends little on the load current. Therefore, although at low current both alkaline and lithium batteries have the same capacity of 3 A*h, if you put them in a digital camera that consumes 1 A, then the alkaline ones will “die” in about thirty minutes, but the lithium ones will live for almost three hours.

The downside of lithium batteries is their high cost: not only is lithium itself expensive, but also due to the danger of it igniting when water gets in, the design of the battery turns out to be noticeably more complex compared to alkaline ones. As a result, one lithium battery costs 100-150 rubles, that is, three to five times more expensive than a very good alkaline one. A Ni-MH battery costs about the same, it has discharge characteristics similar to lithium batteries, but can survive several hundred charge-discharge cycles - so buying lithium batteries is justified only if you have nowhere, no time or nothing to charge conventional batteries.

Yes, since we are talking about charge cycles, it must be said that it is absolutely forbidden to try to charge lithium batteries! If an ordinary alkaline or salt battery, when trying to charge it, can, at most, simply leak, then sealed lithium batteries explode when charged.

Also, in addition to good discharge characteristics, lithium batteries have two more advantages, which, as a rule, are not very significant: durability (the permissible shelf life reaches 15 years, and the battery will lose only 10% of its capacity) and the ability to work at subzero temperatures, when salt batteries and alkaline batteries, the electrolyte simply freezes.

Nickel-cadmium (Ni-Cd) batteries

The main alternative to batteries are batteries - current sources, the chemical processes in which are reversible: when the battery is connected to a load, they go in one direction, and when voltage is applied to it, in the opposite direction. Thus, if after use you have to throw away the battery and buy a new one, then the battery can be charged to its full (or almost full) original capacity.

We will consider batteries used in light household electronic equipment - therefore, heavy (both literally and figuratively) lead-acid batteries found in cars, uninterruptible power supplies and other devices with high power consumption and without special restrictions on weight and dimensions , are immediately left out of our article today. But we will pay much more attention to the various types of nickel batteries...

The first nickel - or, more precisely, nickel-cadmium - batteries were created by the Swedish scientist Waldmar Jungner back in 1899, but at that time they were relatively expensive, and besides, they were not sealed: when charging, the battery emitted gas. Only in the middle of the last century was it possible to create a nickel-cadmium battery with a closed cycle: the gases released during charging were absorbed by the battery itself.

Nickel-cadmium batteries are reliable and durable (they can be stored for up to five years, and charged - if used correctly - up to 1000 times), work well at low temperatures and can easily withstand high discharge currents, and can be charged with both low and high currents.

However, they also have a lot of disadvantages. Firstly, a relatively low energy density (that is, the ratio of the cell’s capacity to its volume), secondly, a noticeable self-discharge current (after several months of storage, the battery will need to be recharged before use), thirdly, the use of poisonous cadmium in the design, and , fourthly, the memory effect.

It’s worth dwelling on the latter in more detail, since when we talk about batteries we will remember it more than once. The memory effect is a consequence of a violation of the internal structure of the battery: crystals begin to grow in it, reducing the effective surface and, accordingly, the battery capacity. The effect got its name due to the fact that the crystals grow especially quickly when the battery is not completely discharged: it seems to remember to what level it was discharged last time - if the battery was discharged, say, only 25%, then the next charge will restore it The capacity is not up to 100%, but less. To combat the memory effect, it is recommended to completely discharge the battery before charging - this destroys the crystals that form and restores the battery capacity. Among the available types of batteries, nickel-cadmium batteries are the most susceptible to memory effect.

However, in some cases, the use of nickel-cadmium batteries is still justified - due to their low cost, durability and the ability to charge at low temperatures without negative consequences for the battery.

Nickel metal hydride (Ni-MH) batteries

Despite their close proximity on store shelves, historically there is a gap between Ni-Cd and Ni-MH batteries: the latter were developed only in the 1980s. Interestingly, the possibility of storing hydrogen for nickel-hydrogen batteries used in space technology was initially studied, but as a result we received one of the most common types of batteries in everyday life.

Unlike nickel-cadmium batteries, nickel-metal hydride batteries do not contain heavy metals, which means they are environmentally friendly and do not require special processing when disposed of. However, this is far from their only advantage: from the point of view of consumers, that is, you and me, it is much more important that with the same dimensions, Ni-MH batteries have two to three times greater capacity - for the most common AA format batteries it reaches already up to 2500-2700 mA*h versus 800-1000 mA*h for nickel-cadmium.

Moreover, Ni-MH batteries also practically do not suffer from the memory effect. More precisely, manufacturers are reducing its influence year after year - and therefore, although theoretically the effect is also present in Ni-MH batteries, in practice it is insignificant in modern models. However, we will not rely on manufacturers for everything and in one of our next articles we will try to evaluate the influence of the memory effect ourselves.

Unfortunately, Ni-MH batteries have their own problems. Firstly, they have a higher self-discharge current (however, we will talk about this again a little later) compared to Ni-Cd, and secondly, although the number of recharge cycles can also reach 1000, a drop in battery capacity can be observed after 200 300 cycles; thirdly, too high discharge currents and charging at low temperatures significantly reduce the life of the battery.

Nevertheless, in terms of the totality of characteristics - cost, reliability, capacity, ease of maintenance - at the moment Ni-MH batteries are one of the best, which led to their use in a huge number of household devices.

Recently, so-called “Ready To Use” Ni-MH batteries have also appeared on sale. They differ from conventional ones in their low self-discharge current - the manufacturer assures that in six months the battery will lose no more than 10% of its capacity, and in a year - no more than 15% (for comparison, a regular Ni-MH battery will drain by 20...30% in a month, and for the year – to zero). Hence the name: being charged by the manufacturer, these batteries will not have time to completely discharge before you buy them in the store, which means they can be used without preliminary charging, immediately after purchase. The disadvantage of such batteries is their smaller capacity - an AA format cell has a capacity of 2000...2100 mAh versus 2600...2700 mAh for conventional Ni-MH batteries.

Chargers for Ni-Cd and Ni-MH batteries

The principles of charging Ni-Cd and Ni-MH batteries are largely similar - for this reason, modern chargers, as a rule, support both types at once. Charging methods and, accordingly, types of chargers can be divided into four groups. In all cases, we will indicate the charging current through the battery capacity: for example, the recommendation to charge with a current of “0.1C” means that a battery with a capacity of 2700 mAh in such a circuit corresponds to a current of 270 mA (0.1 * 2700 = 270) , and a battery with a capacity of 1400 mAh – 140 mA.

Slow charge current 0.1C

This method is based on the fact that modern batteries can easily withstand overcharging (that is, an attempt to “fill” them with more energy than the battery can store) if the charging current does not exceed 0.1C. If the current exceeds this value, the battery may fail when overcharged.

Accordingly, a low-current charger does not need any control over the end of the charge: there is nothing wrong with its excessive duration, the battery will simply dissipate excess energy in the form of heat. Suitable chargers are cheap and widely available. To charge the battery, it is enough to leave it in such a charger for a time of at least 1.6 * C/I, where C is the battery capacity, I is the charging current. Let's say, if we take a charger with a current of 200 mA, then a battery with a capacity of 2700 mAh is guaranteed to charge in 1.6 * 2700/200 = 21 hours 36 minutes. Almost a day... in general, the main disadvantage of such chargers is obvious - the charging time often exceeds reasonable values.

However, if you are not in a hurry, such a charger has a right to life. The main thing is that if you are using low-capacity batteries paired with a modern charger, check that the charging current (and it must be indicated in the charger’s characteristics) does not exceed 0.1C. It is also worth considering that slow charging contributes to the memory effect of batteries.

Charging with current 0.2...0.5C without control of the end of charge

Such chargers, although rare, are still found - mainly among cheap Chinese products. At a current of 0.2...0.5C, they either do not have charge end control at all, or only have a built-in timer that turns off the batteries after a specified time.

Use similar memories absolutely not recommended: since there is no control over the end of the charge, in most cases the battery will be under- or overcharged, which will significantly shorten its life. If you save on a charger, you will lose money on batteries.

Charging current up to 1C with charge end control

This class of chargers is the most universal for everyday use: on the one hand, they charge batteries in a reasonable time (from one and a half to four to six hours, depending on the specific charger and batteries), on the other, they clearly control the end of the charge in automatic mode .

The most common method for monitoring the end of a charge is by voltage drop, usually called the “dV/dt method”, “negative delta method” or “-ΔV method”. It consists in the fact that during the entire charging, the voltage on the battery slowly increases - but when the battery reaches full capacity, it decreases briefly. This change is very small, but it is quite possible to detect it - and, having detected it, stop the charge.

Many charger manufacturers also list "microprocessor control" in their specifications - but, in essence, this is the same as negative delta control: if present, it is carried out by a specialized microprocessor.

However, voltage control is not the only one available: when the battery accumulates full capacity, the pressure and temperature of the case sharply increases, which can also be controlled. In practice, however, it is technically easiest to measure voltage, so other methods for monitoring the end of charge are rare.

Also, many high-quality chargers have two protective mechanisms: battery temperature control and a built-in timer. The first stops charging if the temperature exceeds the permissible limit, the second - if stopping the charge by negative delta did not work within a reasonable time. Both of these can happen if we use old or simply low-quality batteries.

Having finished charging the batteries with a high current, the most “reasonable” chargers continue to charge them for some time with a low current (less than 0.1C) - this allows you to get the maximum possible capacity from the batteries. The charge indicator on the device usually goes off, indicating that the main charging stage is complete.

There are two problems with such devices. Firstly, not all of them are able to “catch” the moment of voltage drop with sufficient accuracy - but, alas, this can only be verified experimentally. Secondly, although such devices are usually designed for 2 or 4 batteries, most of them do not charge these batteries independently of each other.

For example, if the instructions for the charger indicate that it can only charge 2 or 4 batteries at the same time (but not 1 or 3), this means that it has only two independent charging channels. Each of the channels provides a voltage of about 3 V, and the batteries are connected to them in pairs and in series. There are two consequences from this. The obvious thing is that you will not be able to charge a single battery in such a charger (and, say, your humble servant daily uses an mp3 player that runs on exactly one AAA battery). Less obvious is that the end of charge control is also carried out only for a couple batteries. If you use batteries that are not very new, then simply due to technological variation, some of them will age a little earlier than others - and if a pair contains two batteries with different degrees of aging, then such a charger will either undercharge one of them or overcharge the second. Of course, this will only exacerbate the rate of aging of the worse of the pair.

The “correct” charger should allow you to charge an arbitrary number of batteries - one, two, three or four - and ideally, also have a separate charging end indicator for each of them (otherwise the indicator goes out when the last battery is charged). Only in this case will you have some guarantees that each of the batteries will be charged to full capacity, regardless of the condition of the other batteries. Separate charge indicators also allow you to catch prematurely failed batteries: if out of four elements used together, one charges much longer or much faster than the others, then it will be the weak link of the entire battery.

Multichannel chargers have another nice feature: in many of them, when charging half the number of batteries, you can select the charging speed. For example, the Sanyo NC-MQR02 charger, designed for four AA batteries, when charging one or two batteries, allows you to select the charging current between 1275 mA (when installing batteries in the outer slots) and 565 mA (when installing them in the central slots). When three or four batteries are installed, they are charged with a current of 565 mA.

In addition to ease of use, chargers of this type are also the most “useful” for batteries: charging with an average current with control of the end of the charge by a negative delta is optimal from the point of view of increasing the life of the batteries.

A separate subclass of fast chargers is a charger with pre-discharge of batteries. This was done to combat the memory effect and can be very useful for Ni-Cd batteries: the charger will make sure that they are first completely discharged, and only then will it start charging. For modern Ni-MHs, such training is no longer mandatory.

Charging with a current of more than 1C with control of the end of charge

And finally, the last method is an ultra-fast charge, lasting from 15 minutes to an hour, with charge control again using a negative voltage delta. Such chargers have two advantages: firstly, you get charged batteries almost instantly, and secondly, ultra-fast charging allows you to largely avoid the memory effect.

There are, however, also disadvantages. Firstly, not all batteries can withstand fast charging well: low-quality models that have high internal resistance can overheat in this mode until they fail. Secondly, a very fast (15-minute) charge can negatively affect the life of the batteries - again, due to their excessive heating during charging. Thirdly, such a charge “fills” the battery only up to 90...95% of capacity - after which, to achieve 100% capacity, an additional charge with a low current is required (however, most fast chargers do this).

However, if you need ultra-fast battery charging, purchasing a “15-minute” or “half-hour” charger will be a good option. Of course, you need to use only high-quality batteries from large manufacturers with it, and also promptly remove used copies from the batteries.

If you are satisfied with a charge duration of several hours, then the chargers described in the previous section with a charging current of less than 1C and control of the end of charge by a negative delta voltage remain optimal.

A separate issue is the compatibility of chargers with different types of batteries. Chargers for Ni-MH and Ni-Cd are usually universal: any of them can charge batteries of each of these two types. Chargers for Ni-MH batteries with charge termination at a negative delta voltage, even if this is not directly stated for them, can also work with Ni-Cd batteries, but on the contrary - alas. The point here is that the voltage surge, that same negative delta, is noticeably smaller for Ni-MH than for Ni-Cd, so not every charger configured to work with Ni-Cd will be able to “feel” this surge on Ni-MH .

For other types of batteries, including lithium-ion and lead-acid, these chargers are fundamentally unsuitable - such batteries have a completely different charging scheme.

Testing methodology

In the process of testing batteries and voltaic cells in our laboratory, we measure the following parameters, the most important for determining both the quality of the cells (that is, their compliance with the manufacturer's promises) and a reasonable area of ​​​​use:

capacity at various discharge modes;
the value of internal resistance;
self-discharge value (for batteries only);
presence of memory effect (only for batteries).

The main part of the test bench is, of course, an adjustable load that allows you to discharge up to four batteries at a given current at the same time.

To monitor the voltage of all four elements, a Velleman PCS10 digital recorder is used, connected to a computer via a USB interface. The measurement error is no more than 1% (the recorder’s own error is 3%, but we additionally calibrate each of its channels, making appropriate corrections to the final data), voltage measurement resolution is 12 mV, measurement frequency is 250 ms.

The installation diagram is quite simple: these are four separate current stabilizers made on the LM324 operational amplifier (this chip consists of four op-amps in one package) and IRL3502 field-effect transistors. All stabilizers are controlled by one multi-turn variable resistor, so the current on them is set simultaneously - this simplifies setting up the installation for a specific test and minimizes the error in manually setting the current. Possible load change limits are from 0 to 3 A per battery.

To measure voltage, four differential amplifiers are assembled on another LM324 chip, the inputs of which are connected directly to the contacts of the block in which the batteries are installed - this completely eliminates the error introduced by losses on the connecting wires. From the outputs of the differential amplifiers, the signal goes to the recorder.

In addition, the circuit contains a rectangular pulse generator, not shown in the figure above, that periodically turns on and then completely turns off the load. The duration of “zero” at the generator output is 6.0 s, the duration of “one” is 2.25 s. The generator allows you to test batteries in operating mode with a pulsed load and, in particular, determine their internal resistance.

Also, the figure above does not show the installation’s power supply circuit: it is connected to the computer’s power supply, its output voltage (+12 V) is reduced to +9 V by a stabilizer on the 78L09 chip, and the -9 V voltage required for bipolar power supply of the op-amp is generated by a capacitive converter on the chip ICL7660. However, these are already insignificant nuances, which we discuss only in order to prevent in advance questions about the correctness of measurements that may arise from readers knowledgeable in electronics.

To cool the power transistors, feedback shunts and the actual batteries being tested, the entire installation is blown by a standard 12-volt fan of size 80x80x20 mm.

A special program was written to receive and automatically process data from the recorder - fortunately, Velleman supplies very easy-to-use SDKs and sets of libraries for many of its devices. The program allows you to plot voltage graphs on batteries in real time depending on the time elapsed since the start of the test, and also calculate – at the end of the test – their capacity. The latter is obviously equal to the product of the discharge current and the time during which the element reaches the lower voltage limit.

The boundary is selected depending on the type of element and discharge conditions. For batteries at low currents this is 1.0 V - it is simply impossible to discharge them below, as this can lead to irreversible damage to the element; at high currents the lower limit is reduced to 0.9 V in order to properly take into account the internal resistance of the battery.

For batteries, two discharge limits have practical meaning. On the one hand, an element is considered completely empty if the voltage across it drops to 0.7 V - therefore, it is logical to measure the capacity precisely after reaching this level. On the other hand, not all battery-powered devices are capable of operating at voltages below 0.9 V, so it is also of practical importance when the battery is discharged to this level. In our tests we will give both of these values ​​- although many elements, having reached the level of 1.0 V, then discharge very quickly, there are also those that stay between 0.7 V and 0.9 V for a relatively long time.

So, having installed the batteries, set the required current and turned on the recorder, we begin testing. For each type of battery, several discharge modes were selected in order to obtain the most interesting and characteristic results.

For batteries it is:

discharge with low direct current: 250 mA for AA format elements, 100 mA for AAA format;
discharge with high direct current: 750 mA for AA format elements, 300 mA for AAA format;

For Ni-MH batteries this is:

discharge with low direct current: 500 mA for AA format elements, 200 mA for AAA format;
discharge with high direct current: 2500 mA for AA format elements, 1000 mA for AAA format;
discharge with pulsed current: pulse duration 2.25 s, pause duration 6.0 s, current amplitude 2500 mA for AA format elements and 1000 mA for AAA format.

For Ni-Cd batteries of AA format, the discharge modes are the same as for Ni-MH batteries of AAA format - taking into account the similar nominal capacity of the first and second.

If when testing batteries everything is simple - I printed out the packaging, inserted the battery into the unit, started the test - then the batteries must be prepared first, because all of them, except for the "Ready To Use" series mentioned above, are completely discharged at the time of purchase. Therefore, battery testing was carried out strictly according to the following scheme;

measurement of residual capacity at low current (only for "Ready To Use" models);
charger;
high current discharge without measuring capacity (training);
charger;
high current discharge with capacity measurement;
charger;
pulsed current discharge with capacitance measurement;
charger;
low current discharge with capacity measurement;
charger;
exposure for 7 days;
low current discharge with capacity measurement - then the result is compared with that obtained in the previous step and the percentage of capacity loss due to self-discharge for 1 week is calculated;

In battery tests, we use one cell of each brand at each stage. In battery tests - at least two cells of each brand.

To charge batteries we use a Sanyo NC-MQR02 charger.

This is a fast charging charger with control of negative delta voltage and battery temperature, allowing you to charge from one to four (in arbitrary combinations) AA batteries, as well as one or two AAA batteries. The former can be charged with both a current of 565 mA and 1275 mA (if there are no more than two batteries), the latter - with a current of 310 mA per cell. Over several years of regular use, this charger has convincingly proven its high efficiency and compatibility with any batteries, which led to its choice for testing. To avoid loss of capacity due to self-discharge, in all tests, except for the self-discharge test itself, the batteries are charged immediately before starting measurements.

Direct current measurements give a logical picture (an example is shown in the graph above): the voltage on the elements quickly decreases in the first minutes of the test, then reaches a more or less constant level, and at the very end of the test, at the last percent of charge, quickly drops again.

Measurements using pulsed current are somewhat less commonplace. The figure above shows a greatly enlarged section of the graph obtained in such a test: voltage dips on it correspond to the load being turned on, and rises to the load being turned off. From this graph it is easy to calculate the internal resistance of the battery: as you can see, with a current amplitude of 2.5 A, the voltage sags by 0.1 V - accordingly, the internal resistance is 0.1/2.5 = 0.04 Ohm = 40 mOhm. The importance of this parameter will become clearer in our subsequent articles, in which we will compare different types of batteries and accumulators with each other - but for now we will only note that high internal resistance causes not only a voltage “dip” under load, but also a loss of energy accumulated in the batteries to heat themselves.

On a full scale, the pulses merge with each other into a continuous strip, the upper limit of which corresponds to the voltage on the battery without load, the lower limit - with load. From the shape of this strip, you can estimate not only the operating time of the element under a heavy pulse load, but also the dependence of its internal resistance on the depth of discharge: for example, as you can see, in a Sony Ni-MH battery the resistance is almost constant and begins to increase only when it is completely discharged . Good result.

As many of our readers will probably notice, we have chosen very strict discharge modes: the current of 2.5 A is very high, and the 6-second pause between pulses does not allow the element to “rest” properly (as we mentioned above, the batteries, after “resting for a while”, , can partially restore their capacity). However, this was done on purpose in order to clearly and clearly show the differences between batteries of different types and different qualities. In order to get closer to milder real operating conditions, as well as to the conditions under which battery manufacturers measure their capacity, we added discharge modes with a relatively small constant current to the testing.

By the way, manufacturers themselves usually indicate discharge modes in the same way as charging modes - in proportion to the capacity of the element. Let's say, standard measurements of battery capacity should be carried out at a current of 0.2C - that is, 540 mA for a 2700 mAh battery, 500 mA for a 2500 mAh battery, and so on. However, since batteries of the same form factor in our tests are quite similar in characteristics, we decided to test them at fixed currents that do not depend on the nameplate capacity of a particular instance - this greatly simplifies the presentation and comparison of results.

And since we are talking about capacity, it is worth mentioning some deceptiveness of such a generally accepted unit as the ampere hour. The fact is that the energy stored in the battery is determined not only by how long it held a given current, but also by what voltage it had at the same time - so, it is quite obvious that a lithium battery with a capacity of 3 Ah and a voltage of 3 B is capable of storing twice as much energy as a battery with a capacity of the same 3 A*h, but with a voltage of 1.5 V. Therefore, it is more correct to indicate the capacity not in ampere-hours, but in watt-hours, obtaining them through the integral of the dependence of the voltage on the battery on time discharge at constant current. In addition to naturally taking into account the different operating voltages of different elements, this technique also allows us to take into account how well this particular element held voltage under load. Say, if two batteries were discharged to 0.7 V in 60 minutes, but the first was kept at 1.1 V for most of this time, and the second at 0.9 V, it is quite obvious that the first has a larger actual capacity - despite the fact that the final discharge time is the same. This is especially important in light of the fact that most modern electronic devices do not consume constant current, and constant power– and elements with high voltage in them will operate in more favorable modes.

Closer to practice: examples of energy consumption

Of course, in addition to abstract testing of batteries on a controlled load, we were interested in how real devices consume current. To clarify this issue, we looked around the surrounding space and randomly selected a set of objects powered by various batteries.

Only part of this set

If the device consumed more or less constant current, measurements were carried out with a conventional Uni-Trend UT70D digital multimeter in ammeter mode. If the current consumption changed significantly, we measured it by connecting a low-resistance shunt between the device and the batteries powering it, the voltage drop across which was recorded with a Velleman PCSU1000 oscilloscope.

The results are presented in the table below:

Well, among our devices there were also quite “gluttonous” ones - a flash, a camera and a flashlight with an incandescent lamp. If the latter consumed the allotted 700 mA constantly and continuously, then the nature of the energy consumption of the first two turned out to be more interesting.

The value of the vertical division in the oscillograms below is 200 mA, zero corresponds to the first division from the bottom.

Camera
Oscillogram division price – 200 mA

In normal mode, the Canon PowerShot A510, powered by two AA batteries, consumed about 800 mA - a lot, but not a record high. However, when turned on (the first group of narrow peaks on the oscillogram), lens movement (the second group of peaks) and focusing (the third group), the current could increase by more than one and a half times, up to 1.2...1.4 A. What’s interesting is that immediately After pressing the shutter, the camera's power consumption dropped - when recording a frame just taken on a flash drive, it automatically turns off the screen. However, as soon as the frame was recorded, the consumption rose back to 800 mA.

Photoflash
Oscillogram division price – 100 mA

The Pentax AF-500FTZ flash (four AA format elements) consumed current even more interestingly: it was almost zero in the periods between firings, instantly grew to 700 mA immediately after firing (this moment is captured on the oscillogram above), and then for 10. ..15 seconds smoothly decreased back to zero (the jagged line of the oscillogram was due to the fact that the flash consumes current with a frequency of about 6 kHz). At the same time, the flash demonstrated a clear relationship between the decay time of the current and the voltage of the elements supplying it: since it needed to accumulate a certain energy each time, the more the supply voltage sagged under load, the more time it took to accumulate the required reserve. This, by the way, well illustrates one of the roles of the internal resistance of batteries - the lower it is, the less, other things being equal, the voltage will drop and the faster you can take the next shot with flash.

In our next articles, where we will consider specific types and instances of batteries and accumulators, a rough idea of ​​the energy needs of different devices will help us determine which batteries are suitable for them.
page 4

Low current chargers

Rice. 14.15. Charger circuit for nickel-cadmium batteries

The diagram shows the ratings for charging TsNK-0.45 batteries. The charger also allows you to charge batteries of types D-0.06, D-0.125, D-0.25, but for each of them it is necessary to install a resistor in the transistor base circuit that provides the corresponding initial charge current.

The charger does not have an overload protection system. The device is powered from a stabilized +5 V source with a maximum current of 2 A.

It should be noted that you should not discharge batteries below 1 6, such batteries lose their nominal capacity, and sometimes they are reversed.

To monitor the end of charging, you can use the circuit in Fig. 14.16.

Rice. 14.16. End of charge control circuit

It is based on the comparator DA1. The non-inverting input receives a voltage of 1.35 B from the adjustable resistor R1. Through the contacts of the SB1 button, voltage from the controlled battery is supplied to the inverting input. If, when the SB1 button is fixed in the pressed position, the HL1 LED begins to light, then the battery has been charged to a nominal voltage of 1.35 V. Next, the voltage on the next battery is monitored, etc.

An automatically shut-off charger based on a thyristor switch (Fig. 14.17) consists of a rectifier and a source of stabilized reference voltage. The reference voltage source is made using a zener diode VD6. Through a resistive divider (potentiometer R2), a stabilized voltage is supplied to the base of transistor VT2. A VD7 diode is connected to the emitter of this transistor by its anode, connected by its cathode to the battery being charged. As soon as the voltage on the battery rises above a predetermined level, transistors VT1 and VT2, as well as the thyristor through which the charging current flows, will turn off, interrupting the charging process.

It is worth noting that the thyristor is powered by rectified voltage pulses from the diode bridge VD1 - VD4. Filter capacitor C1, transistor circuit and voltage stabilizer are connected to the rectifier via diode VD5. The incandescent lamp indicates the charging process and, if necessary, limits the short circuit current in an emergency.

Chargers can also use a current stabilizer circuit. In Fig. Figure 14.18 shows a charger circuit based on the LM117 chip with charging current limited to 50 mA. The magnitude of this current can be easily changed using resistor R1.

Rice. 14.17. Charger circuit with automatic shutdown

Rice. 14.18. Charger circuit based on current stabilizer

Rice. 14.19. Charger circuit for charging a 12V battery

A simple charger for charging a 12 V battery can be made based on an LM117 type microcircuit (Fig. 14.19). The output resistance of the device is determined by the value of the resistor Rs.

The circuit of another charger with a charging current limiter at 600 mA (with a resistance of resistor R3 = 1 Ohm) for charging a 6 V battery is shown in Fig. 14.20.

Rice. 14.20. Charger circuit with charging current limitation

Rice. 14.21. Charger diagram for TsNK-0.45 batteries

In the charger circuit (Fig. 14.21), a current stabilizer on a microcircuit of type KR142EN5A is used to charge batteries of the TsNK-0.45 type. The charge current (50...55 mA) is set by the resistance of resistor R1: exactly 5 V drops across this resistance, therefore, the current flowing through the series chain of the battery being charged and the stable current generator based on the DA1 microcircuit is ( B)/120 (Ohm)=45+\s (mA), where 1C=5...10 mA is the microcircuit’s own consumption current. In reality, the current will be higher than the specified value by another 3 mA, since the calculations do not take into account the current through the HL1 LED indicator, which indicates the operation of the device.

The voltage across filter capacitor C1 should be about 15...25 V.

When using stabilizers for a higher output voltage, the value of resistor R1 should be changed (increasing).

The device can be used with almost no modifications for other charging currents, up to 1 A. This will require the selection of resistor R1 and, if necessary, the use of a heatsink for the DA1 chip.

The charger (see Fig. 14.22) is supplied with a rectified voltage of 12 V. The resistance of current-limiting resistors is calculated using the formula: R=UCT/I, Where UCT– output voltage of the stabilizer; I– charging current. In the case under consideration, UCT=1.25 B; accordingly, the resistance of the resistors is as follows: R1=1.25/0.025=50 Ohm, R2=1.25/0.0125=100 Ohm. The calculations do not take into account the current consumption of the microcircuit (see above), which can be 5... 10 mA.

Rice. 14.22. Charger circuit with current stabilization

The device can use microcircuits of types SD1083, SD1084, ND1083 or ND1084.

The diagram of the foreign charger "VS-100" is shown in Fig. 14.23. The device allows you to simultaneously charge 3 pairs of Ni-Cd batteries. During the charging process, the HL1 LED lights up, then the HL1 LED begins to flash periodically. The constant lighting of LEDs HL1 and HL2 indicates the end of the charging process.

The VS-100 charger is not without its drawbacks. Charging the most common batteries with a capacity of 450 mAh with a current of 160 ... 180 mA turns out to be unacceptable. Not all batteries can withstand the accelerated charging mode, so O. Dolgov developed a more advanced charger, the diagram of which is shown in the following figure (Fig. 14.24).

The mains voltage, reduced by transformer T1 to 10 V, is rectified by diodes VD1 - VD4 and through the current-limiting resistor R2 and the composite transistor VT2, VT3 is supplied to the charging battery GB1. LED HL1 indicates the presence of charging current.

Rice. 14.23. Scheme of the charger "VS-100" for Ni-Cd batteries

Rice. 14.24. Scheme of an improved charger for Ni-Cd batteries

The value of the initial charge current is determined by the voltage of the secondary winding of the transformer and the resistance of resistor R2. But the voltage at the output of the device is not enough to open the zener diode VD5, so transistor VT1 is closed, and the composite transistor is open and in a state of saturation. When the battery voltage reaches 2.7…2.8 V, transistor VT1 opens, LED HL2 lights up, and the composite transistor, closing, reduces the charge current.

The secondary winding of the mains transformer must be designed for a voltage of 8...12 V and a maximum charging current, taking into account all simultaneously charged batteries. The initial charge current of the proposed device is about 100 mA.

Setting up the device comes down to setting the maximum charge current and output voltage at which the HL2 indicator starts to light. A pair of discharged batteries is connected to the output of the device via a milliammeter and the required charging current is set by selecting resistor R2. Then the emitter output of transistor VT3 is temporarily disconnected from external circuits, a pair of fully charged batteries (or another source with a voltage of 2.7...2.8 V) is connected to the output of the device, and by selecting resistors R5 and R6, LED HL2 lights up. After this, the open connection is restored - and the device is ready for operation.

To charge nickel-cadmium batteries, V. Sevastyanov used a current stabilizer based on an integrated circuit DA1 type KR142EN1A (Fig. 14.25). The amount of charging current is controlled roughly and smoothly using resistors R3 and R4.

The microcircuit itself can provide a rated output current of up to 50 mA and a maximum output current of up to 150 mA. If it is necessary to increase this current, you should connect a transistor amplifier using a composite transistor. The transistor must be installed on the radiator. In the version shown in Fig. 14.25, the device provides an output regulated stable current within the range of 3.5…250 mA.

Charged elements are connected to the device via diodes VD1 - VD3.

To charge D-0.06 batteries, the total charging current is set within 16... 18 mA; The charge with this current is carried out for 6 hours, then the charging current is reduced by half and the charge is continued for another 6 hours.

Rice. 14.25. Current stabilizer circuit for charging Ni-Cd batteries

Rice. 14.26. Diagram of a device for restoring silver-zinc elements STs-21

To recharge the silver-zinc elements STs-21, V. Pitsman used a circuit (Fig. 14.26), which is based on a master oscillator based on a transistor and a K155LAZ microcircuit. Connected to pins 8 and 11 of the DA1 microcircuit are diode chains formed from series-connected silicon diodes KD102, with a germanium diode D310 connected back-to-back parallel to them.

Thanks to this inclusion, when the values ​​of logical zero and logical one alternately appear at the output of the microcircuit (i.e., connecting a chain of diodes to the positive or common bus of the power source), the elements GB1 and GB2 are alternately dosed, followed by their discharge. The magnitude of the charging current exceeds the discharge current, which ultimately helps restore the properties of the elements.

High Power Chargers

When a battery is stored idle for a long time, it becomes unusable as a result of natural self-discharge and sulfation of the plates.

To ensure that long-term storage does not lead to damage to the battery, it must be constantly maintained in a charged state. Manufacturers recommend charging batteries with a current equal to 0.1 of the nominal capacity (i.e. for 6ST-55, the charge current will be 5.5 A), but this is only suitable for quickly charging a “depleted” battery. As practice shows, to recharge a battery during long-term storage, a small current is required, about 0.1...0.3 A (for 6ST-55). If a stored battery is periodically, approximately once a month, placed on such a charge for 2...3 days, then you can be sure that it will be ready for use at any time, even after several years of such storage.

In Fig. Figure 16.6 shows a diagram of a “recharging” device - a transformerless power source that produces a constant voltage of 14.4 V at a current of up to 0.3 A. The source is built according to the circuit of a parametric stabilizer with capacitive ballast resistance. The voltage from the network is supplied to the bridge rectifier VD1 - VD4 through capacitor C1. At the output of the rectifier, a 14.4 V zener diode VD5 is switched on. Capacitor C1 limits the current to a value of no more than 0.3 A. Capacitor C2 smoothes out the ripples of the rectified voltage. The battery is connected in parallel with the zener diode VD5.

Rice. 16.6. Diagram of a device for recharging batteries

When the battery self-discharges to a voltage below 14.4 V, its “soft” charge with a low current begins. The magnitude of this current is inversely dependent on the voltage on the battery, but in any case, even with a short circuit, does not exceed 0.3 A. When the battery is charged to a voltage of 14.4 V, the process stops.

When operating the device, you must follow safety rules when working with electrical installations.

A simple charger for charging car or tractor batteries (Fig. 16.7) has the advantage of increased safety in operation compared to transformerless analogues. However, its transformer is quite complex: it has many taps to regulate the charging current.

The charge current is adjusted by the slide switch S1 by changing the number of turns of the primary winding. The rectifier provides a charging current of 10... 15 A.

A portable device designed to charge lithium (lithium ion) batteries with pulsating current is shown in Fig. 16.9. The automated charger is made on the basis of a specialized microcircuit from MAXIM - MAX1679. The charger receives power from an AC adapter capable of delivering a voltage of 6 V at a current of up to 800 mA. To protect the circuit from incorrect connection, the VD1 diode is used - a Schottky diode - designed for a forward current of 1 A at a maximum reverse voltage of 30 V. The HL1 LED is designed to indicate the operation of the charger.

Rice. 16.8. Diagram of a device for charging 12-volt batteries with a current of 1 to 15 A

Rice. 16.9. Charger circuit for lithium ion batteries based on the MAX1679 chip

Rice. 16.10. Boost converter circuit for charging a 13.8 V battery of a VHF radio station from the vehicle’s on-board network

To increase the stability of the device when the ambient temperature changes from 0 to 50 °C, an R2 type thermistor is used NTC FENWAL 140-103LAG-RBI, having a resistance of 10 kOhm at a temperature of 25 °C.

The lithium ion cell voltage is 2.5V per cell.

A simple charger designed to recharge a battery with a voltage of 13.8 B from the vehicle's on-board network (about 12 V), is made on the basis of a step-up voltage converter based on the LT1170CT chip. 16.10). The microcircuit produces pulses with a frequency of 00 kHz. These pulses arrive at the internal key stage of the microcircuit (its output is pin 4). A chain of resistive elements R2, R3 is designed to monitor fluctuations in the output voltage and organize voltage tracking feedback (pin 2 of the microcircuit). The output voltage is regulated by selecting these resistors. The rectifier of the converter is made on diode VD2 - Schottky diode type MBR760 direct current up to 5/4).

The battery charging current is up to 2 A, the efficiency of the converter reaches 90%.

Reconditioning of passivated batteries

As a result of improper use of batteries, their plates become passivated and fail. However, there is a known method for restoring such batteries with an asymmetric current (with a ratio of charging and discharging components of this current of 10:1 and a pulse ratio of these components of 1:2). This method allows you to activate the surfaces of the plates of old batteries and carry out preventive maintenance on working ones [2].

Rice. 1. Charging the battery with asymmetric current. Electrical circuit diagram

In Fig. Figure 1 shows a battery charging circuit with asymmetric current, designed to work with a 12 V battery and provides a pulse charging current of 5 A and a discharge current of 0.5 A. It is a current regulator assembled on transistors VT1...VT3. The device is powered by an alternating current voltage of 22 V (amplitude value 30 V). At the rated charging current, the voltage on a charged battery is 13...15 V (average voltage 14 V).

During one period of alternating voltage, one charging current pulse is formed (cut-off angle a = 60ْ). In the interval between charging pulses, a discharge pulse is formed through resistor R3, the resistance of which is selected according to the required amplitude of the discharge current. It must be taken into account that the total current of the charger should be 1.1 times the battery charging current, since when charging, resistor R3 is connected in parallel to the battery and current flows through it. When using an analog ammeter, it will indicate about one-third the amplitude of the charging current pulse. The circuit is protected against output short circuit.

The battery is charged until abundant gas evolution (boiling) occurs in all banks, and the voltage and density of the electrolyte remain constant for two hours in a row. This is a sign of the end of the charge. Then you should equalize the density of the electrolyte in all banks and continue charging for about 30 minutes to better mix the electrolyte.

When charging the battery, you should monitor the temperature of the electrolyte and not allow it to exceed: 45ْ C in temperate and cold zones and 50ْ C in warm and hot humid climate zones.

Since hydrogen is released when charging acid batteries, you should charge the batteries in well-ventilated areas, and you should not smoke or use open flame sources. The resulting explosive mixture has great destructive power.

(The gas released when the electrolyte boils carries droplets of acid, which, when they enter the respiratory system, onto the mucous membrane of the eyes, skin, corrode them, so it is better to charge batteries in the open air outside - U.A.9 LAQ).

Literature: 1. Batteries and Accumulators. Series “Information publication”.

Issue 1. “Science and Technology”, Kyiv, 1995, pp. 30...31.

2. Deordiev S.S. Batteries and their care. Equipment, Kyiv, 1985

P. S. The topic is relevant for everyone who uses high-power autonomous power supply, for mobile (mobile) radio stations, participants in radio expeditions and “Field Days”. It is better to install transistors VT2 and VT3 on heat sinks with sufficient surface area. It is better to make powerful low-resistance resistors from copper wire, winding it around a frame made of non-flammable, refractory material. It is possible to manufacture such resistors from high-resistance wire or use powerful low-voltage incandescent lamps. Since the latter have a variable resistance, on the one hand, they can cause instability of the protection threshold; on the other hand, when connected in series, they will be (additional) current stabilizers (here: charging current).

For sealed batteries with gel electrolyte, along with a cyclic gentle charging mode with a constant current, they use a floating charging current mode at a constant voltage, in which case it is necessary to set the voltage to 2.23...2.3 V per battery cell, which in terms of for example, for a 12-volt battery it will be: 13.38...13.8 V. When the temperature changes from minus 30° C to plus 50° C, the charge voltage can change from 2.15 to 2.55 V per cell. At a temperature of 20ْ C when using a battery in buffer mode, the voltage on it should be in the range of 2.3...2.35 V per cell. Voltage fluctuation (for example, when changing the load on a combined power supply with a “buffer” battery) should not exceed plus/minus 30 mV per element. When charging voltages are greater than 2.4 V per cell, measures should be taken to limit the charging current to a maximum of 0.5 A per amp-hour of capacity.

When using a battery in a buffer with a voltage stabilizer, the voltage at the output of the latter should be selected so that it does not exceed the voltage of a freshly charged battery, for example, 14.2 V for a 12-volt battery, taking into account the voltage drop across the isolation diode (between the stabilizer and the battery), which should be selected with a margin for the maximum load current and battery charging current (unless the possibility of connecting a discharged battery is excluded).

The diode must have the maximum possible reverse and minimum possible forward resistance to ensure, respectively, minimal discharge of the battery through the stabilizer disconnected from the network and a minimum drop in the charging voltage when changing the load as indicated above. Powerful Schottky barrier diodes work well here.

The principles outlined above are, for the most part, acceptable for miniature non-acid batteries, but the voltages and currents are different.

A few words about the regeneration of galvanic cells.

Rice. 2. Charging galvanic cells with asymmetric current. Basic electrical diagram.

In [1], a simple scheme for charging galvanic cells with an asymmetric current is given, when two diodes are connected to the secondary winding of a step-down transformer according to a half-wave rectification circuit of positive and negative voltage. A two-watt resistor with a resistance of 13 Ohms is connected in series with one diode (for direct charging current), and in series with another, connected in the opposite polarity, the same resistor, but with a resistance of 100 Ohms, to provide the discharge current. Both circuits are connected to a galvanic cell or battery of them. (Fig. 2). By the magnitude of the voltage supplied to the input of the rectifiers or the value of the resistor values ​​in the available proportion, you can synchronously change the charge and discharge current of galvanic current sources. The ratio of charging current to discharge current is 10:1, the ratio of pulse duration is 1:2. As indicated in [1], the device allows you to activate watch batteries and old small batteries. Moreover, the charge of the former should be carried out with a current of no more than 2 mA and last no more than 5 hours.

At one time, I used the “floating” method of charging galvanic cells, which allowed me to operate three 9-volt sets of 316 “Prima” elements for a couple of years and, for a total of 4 years, when the elements combined into one “survived” from the three sets . The elements were taken new: literally two weeks after release they arrived at my place, a preliminary selection for identity was carried out and the operating procedure was thought out. The charging mode I selected provided charging current for 12...15 hours from a stabilized power supply with an output voltage of 9.6 V, i.e., 1.51 V per element (up to 1.52...1.53 V is possible). This mode prevents the elements from heating up when charging, which means that the elements do not dry out for a long time. The battery was operated in a CB radio station with an output power of up to 1 W (VIS-R). The elements were not stored in a discharged state; operation was carried out in a buffer (stabilizer plus battery) in stationary conditions and in field conditions, after returning from which, the battery (inside the station) was returned to its place again: to the stabilizer.

Many people have receivers, children's toys and other devices powered by galvanic cells. Today, the cost of batteries, compared to the level of wages, is quite high, and they are not always and everywhere available for free purchase in stores. The editors hope that the proposed selection of articles will help you solve the problem of powering portable devices.

The problem of reusing galvanic batteries has long been of concern to electronics enthusiasts. Various methods for reviving elements have been repeatedly published in the technical literature, but as a rule, they only helped for one time, and they did not gain the expected capacity.

B. I. Bogomolov devoted about 14 years to the problem of restoration (regeneration) of galvanic batteries and, perhaps, readers will be interested in getting acquainted with his work in this area. As a result of experiments, B.I. Bogomolov was able to determine the optimal current regeneration modes and develop a charger for most elements. They sometimes acquired a capacity slightly greater than the original one. It is necessary to restore the cells, not the batteries from them, since even one of the series-connected battery cells that has become unusable (discharged below the permissible level) makes it impossible to restore the battery.

As for the charging process, it should be carried out with an asymmetric current with a voltage of 2.4...2.45 V. At a lower voltage, regeneration is very delayed and the cells do not reach half their capacity after 8...10 hours of charging. At higher voltages, there are often cases of elements boiling, and they become unusable.

Before you start charging the element, it is necessary to carry out its diagnostics, the meaning of which is to determine the ability of the element to withstand a certain load. To do this, first connect a voltmeter to the element and measure the residual voltage, which should not be lower than 1 V. An element with a lower voltage is unsuitable for regeneration.

Then the element is loaded for 1...2 seconds. a 10 Ohm resistor and if the cell voltage drops by no more than 0.2 V, it is suitable for regeneration. The electrical circuit of the charger (Fig. 1) is designed to simultaneously charge 6 cells (G1...G6 type 373, 316, 332, 343 and other similar MI).

The most important part of the element recharging device is the transformer, since the voltage in its secondary winding must be strictly within the range of 2.4...2.45 V, regardless of the number of regenerated elements connected to it as a load.

If it is not possible to find a ready-made transformer with such an output voltage, then you can adapt an existing transformer with a power of at least 3 W by manually winding a secondary winding on it to the required voltage with a PEL or PEV wire with a diameter of 0.8...1.2 mm. The connecting wires between the transformer and the charging circuits should be as large as possible.

The duration of regeneration is 4...5, and sometimes 8 hours. Periodically, one or another element must be removed from the regeneration unit and checked according to the method given above for diagnosing elements, or you can use a voltmeter to monitor the voltage on the charged elements and as soon as it reaches 1.8...1.9 V, regeneration stop, otherwise the element may overcharge and fail. The same applies if any element is heated.

Elements that work in children's toys are best restored if they are put on regeneration immediately after discharge. Moreover, such elements, especially with zinc cups, allow for reusable regeneration. Modern elements in a metal case behave somewhat worse.

In any case, the main thing during regeneration is to prevent deep discharge of the element and set it up for regeneration in a timely manner, so do not rush to throw away used galvanic cells.

The second circuit, shown in Fig. 2, uses the same principle of recharging the elements with a pulsating asymmetric electric current. It was proposed by S. Glazov and is easier to manufacture, since it allows the use of any transformer with a winding having a voltage of 6.3 V. The NL incandescent lamp (6.3 V; 0.22A) not only performs signal functions, but also limits the charging current element, and also protects the transformer in case of short circuit in the charging circuit.

Zener diode VD1 type KS119A limits the charge voltage of the element. It can be replaced by a set of series-connected diodes - two silicon and one germanium - with a permissible current of at least 100 mA. Diodes VD2 and VD3 - any silicon with the same permissible average current, for example KD102A, KD212A. The capacitance of capacitor C1 is from 3 to 5 µF for an operating voltage of at least 16 V. A circuit of switch S1 and test sockets X1, X2 for connecting a voltmeter. Resistor R1 - 10 Ohm and button S2 are used to diagnose element G1 and monitor its condition before and after regeneration. The normal state corresponds to a voltage of at least 1.4 V and its decrease when connecting a load by no more than 0.2 V. The degree of charge of the element can be judged by the brightness of the NL lamp. Before the element is connected, it glows at approximately full intensity; when a discharged element is connected, the brightness of the glow increases noticeably, and at the end of the charging cycle, connecting and disconnecting the element causes almost no change in brightness.

When recharging elements such as STs-30, STs-21 and others (for wristwatches), it is necessary to connect a 300...500 Ohm resistor in series with the element. Battery cells of type 336 and others are charged alternately. To access each of them you need to open the cardboard bottom of the battery.

Charging a battery without a circuit

Batteries for watches are in short supply. You can still buy elements like “Mars” or “Saturn,” although they are already a bit expensive. N. Galivanov tried to recharge a dead watch battery using these elements. Connected plus to plus, minus to minus. Happened. After 12 hours the battery powered the watch like new. After updating, the STs-21 battery in the Elektronika-5 watch can last 6-8 months.

But N. Galivanov warns: before inserting a recharged battery into the watch, you need to check the voltage at its output: it should not exceed 1.5 V.

It has been practically established that the most common cup-type manganese-zinc cells and batteries, such as 3336L (KBS-L-0.5), 3336X (KBS-X-0.7), 373, 336, can be regenerated better than others. manganese-zinc batteries "Krona VTs", BASG and others.
The best way to regenerate chemical power sources is to pass through them an asymmetrical alternating current having a positive direct component. The simplest source of asymmetric current is a half-wave rectifier using a diode shunted by a resistor. The rectifier is connected to the secondary low-voltage (5-10 V) winding of a step-down transformer powered by an alternating current network. However, such a charger has a low efficiency - approximately 10% and, in addition, the battery being charged may be discharged if the voltage supplying the transformer is accidentally turned off.
Better results can be achieved if you use a charger made according to the circuit shown in Fig.
1. In this device, the secondary winding II powers two separate rectifiers on diodes D1 and D2, to the outputs of which two rechargeable batteries B1 and B2 are connected.

rice. 1
Capacitors C1 and C2 are connected in parallel with diodes D1 and D2. In Fig. Figure 2 shows an oscillogram of the current passing through the battery. The shaded portion of the period is the hour during which pulses of discharge current flow through the battery.

EXPAND THE DIAGRAM IN FULL SCREEN

rice. 2
These pulses obviously have a special effect on the course of electrochemical processes in the active materials of galvanic cells. The processes occurring in this case have not yet been sufficiently studied and there are no descriptions of them in the popular literature. In the absence of discharge current pulses (which happens when a capacitor connected in parallel with the diode is disconnected), the regeneration of the elements practically stopped.
It has been experimentally established that manganese-zinc galvanic cells are relatively little critical to the magnitude of the constant component and the shape of negative charging current pulses. This allows the charger to be used without additional adjustment of the DC and AC components of the charging current for recovery of various cells and batteries. The ratio of the constant component of the charge current to the effective value of its variable component should be in the range of 5-25.
Charger performance can be improved by enabling multiple cells to be charged in series. It must be taken into account that during the charging process, e.g. d.s. elements can increase to 2-2.1.v. Based on this and knowing the voltage on the secondary winding of the transformer, the number of simultaneously charged elements is determined.
It is more convenient to connect type 3336L batteries to the charger through a 2.5V X 0.2A incandescent light bulb, which plays the role of a barter and at the same time serves as an indicator of the state of charge. As the battery's electrical charge is restored, the glow of the light bulb decreases. Elements of the “Mars” type (373) must be connected without a light bulb, since the constant component of the charging current of such an element should be 200-400 mA. Elements 336 are connected in groups of three, connected in series. The charging conditions are the same as for batteries of type 3336. The charging current for elements 312, 316 should be 30-60 mA. It is possible to simultaneously charge large groups of 3336L (3336X) batteries directly from the network (without a transformer) through two D226B diodes connected in series, parallel to which a 0.5 μF capacitor with an operating voltage of 600 V is connected.
The charger can be made on the basis of a Molodist electric razor transformer, which has two secondary windings with a voltage of 7.5 V. It is also convenient to use the 6.3 V filament voltage of any network tube radio. Naturally, one or another solution is chosen depending on the required maximum charging current, determined by the type of elements being restored. The same is true when choosing rectifier diodes.

EXPAND THE DIAGRAM IN FULL SCREEN

rice. 3
In order to evaluate the effectiveness of this method for restoring galvanic cells and batteries, in Fig. Figure 3 shows discharge voltage graphs for two 3336L batteries with load resistance Rн=10 ohms. Solid lines show the discharge curves of new batteries, and dotted lines show after twenty complete discharge-charge cycles. Thus, the performance of the batteries after twenty times of use is still completely satisfactory.
How many discharge-charge cycles can galvanic cells and batteries withstand? Obviously, this greatly depends on operating conditions, shelf life and other factors. In Fig. Figure 4 shows the change in discharge time to a load Rн=10 ohm of two 3336L batteries (curves 1 and 2) during 21 discharge-charge cycles. The batteries were discharged to a voltage of at least 2.1 V, the charging mode of both batteries was the same. During the specified operating time of the batteries, the discharge hour decreased from 120-130 minutes to 50-80 minutes, that is, almost half.

EXPAND THE DIAGRAM IN FULL SCREEN

rice. 4
The same reduction in capacity is allowed by technical conditions at the end of the established maximum shelf life. It is practically possible to restore cells and batteries until their zinc cups are completely destroyed or the electrolyte dries out. It has been established that elements that are intensively discharged to a powerful load (for example, in flashlights, in power supplies for electric shavers) can withstand more cycles. Cells and batteries should not be discharged below 0.7V per ingredient. The recoverability of elements 373 is relatively worse, since after 3-6 cycles their capacity decreases sharply.
The required charge duration can be concluded using the graph; shown in Fig.
4. When the charging time increases beyond 5 hours, the restored battery capacity increases on average very slightly. Therefore, we can assume that at the indicated values ​​of the charging current, the minimum recovery hour is 4-6 hours, and manganese-zinc cells do not have obvious signs of the end of the charge and are insensitive to overcharging.
The use of asymmetrical current also proves useful for charging and forming batteries and storage batteries. This issue, however, still requires testing in practice and may open up new interesting possibilities for batteries.
(Radio 6-72, p.55-56)

http://www. /load/16-37/index. html

http:///document4979.html

To restore the functionality of batteries (multiple chargeable galvanic cells based on the reversible conversion of electrical energy into chemical energy and vice versa), special chargers are used that allow one to “pump” another jolt of energy into a discharged battery. Unlike batteries, galvanic cells and disposable batteries were not originally intended to be recharged (otherwise they would have had a different name). However, during the operation of some galvanic cells and batteries, the possibility of partially restoring their properties by charging was revealed.
Several methods are used to charge batteries, the main one of which is DC charging. In addition to the classical one, they use the method of charging according to the ampere-hour rule, charging with pulsating and/or symmetrical current, charging at a constant voltage, increasing alternating charge-discharge with an adjustable ratio and predominance of the charging component, express charge, step-current charge, “floating” charge , empensary recharge, etc.
Good results are obtained by charging the battery with a current that varies in accordance with the so-called “amp-hour law” of Woodbridge. At the beginning of charging, the current is maximum and then decreases according to the law described by an exponential curve. When charging according to the "amp-hour law", the current can reach 80% of the battery capacity, resulting in significantly reduced charging time.
Each of the listed methods has both advantages and disadvantages. The most common and reliable is DC charging. The advent of voltage stabilizer microcircuits that allow operation in current abilization mode makes the use of this method even more attractive. In addition, only direct current charging provides the best restoration of battery capacity when the process is divided, as a rule, into two stages: charging with the rated current and half the current.
For example, the nominal voltage of a battery of four D-0.25 batteries with a capacity of 250 mAh is 4.8...5 V. The nominal charging current is usually chosen equal to 0.1 of the capacity, i.e. 25 mA. They charge with this current until the voltage on the battery reaches 5.7...5.8 V with the charger terminals connected, and then continue to charge for two to three hours with a current of about 12 /i/A.
The possibility of increasing the service life of dry galvanic cells (regeneration method) was laid down by Ernst Weer's patent in 1954 (US Patent). Regeneration is carried out by passing an asymmetric alternating current with a half-cycle ratio of 1:10 through a galvanic cell or a group of them. According to various authors, the average service life of galvanic cells can be increased in this way from 4 to 20 times.
According to the practical recommendations of the Warta company (Germany):

Elements whose voltage is below the nominal value by no more than 10% can be regenerated; the voltage for element regeneration should not exceed the nominal value by more than 10%; the regeneration current must be within 25...30% of the maximum discharge current for a given element; the regeneration time should be 4.5...6 times greater than the discharge time; regeneration should be carried out immediately after the battery is discharged; Regeneration should not be carried out for cells with a damaged zinc body or leaked electrolyte.

In addition to charging and discharging operations, for some types of batteries, an urgent issue is the regeneration (restoration), as far as possible, of their original properties lost as a result of improper storage and/or operation.
Techniques for “reanimation” and restoration of resources of discharged electric batteries (dry galvanic batteries and cells) are generally similar and sometimes correspond to the corresponding procedures for batteries.
Devices for charging, restoring or regenerating chemical current sources usually contain a current stabilizer, sometimes an overvoltage or overcharging protection device, control and regulation devices and circuits.
For example, in practice, several types of chargers have become widespread for nickel-cadmium batteries.

1. Fixed constant current charger. Charging the battery is stopped manually after sufficient time has elapsed for a full charge. The charging current should be 0.1 of the battery capacity for 12 hours.

2. The charging current is fixed. The voltage on the battery being charged is controlled by a threshold device. When the set voltage is reached, charging automatically stops.

3. The charger charges the battery with constant current for a fixed time. Charging automatically stops after, for example, 15 hours. The latest version of the charger has a significant drawback. Before charging, the battery must be discharged to a voltage of 1 V; only then, when charging with a current of 0.1 of the battery capacity for 15 hours, will the battery be charged to its nominal capacity. Otherwise, when charging a battery that is not completely discharged for the specified time, it will be overcharged, which will lead to a reduction in service life.

In the first two versions of devices, charging with a constant stable current is not optimal. Research has found that at the very beginning of the charging cycle, the battery is most susceptible to the amount of electricity supplied to it. Toward the end of charging, the battery's energy storage process slows down.

DIAGRAMS OF DEVICES FOR REGENERATION OF GALVANIC
BATTERIES

Author of the article: Unknown

google_protectAndRun("render_ads. js::google_render_ad", google_handleError, google_render_ad); The problem of reusing voltaic batteries has long been of concern to electronics enthusiasts. Various methods of “revitalizing” elements have been repeatedly published in the technical literature, but, as a rule, they helped only once, and did not provide the expected capacity.

As a result of the experiments, it was possible to determine the optimal current regeneration modes and develop chargers suitable for most cells. At the same time, they regained their original capacity, and sometimes even slightly exceeding it.

It is necessary to restore the cells, not the batteries from them, since even one of the series-connected battery cells that has become unusable (discharged below the permissible level) makes it impossible to restore the battery.

As for the charging process, it must be carried out with an asymmetrical current with voltage 2.4...2.45 V. At lower voltages, regeneration is very delayed and the elements after 8...10 hours They don’t fill even half the capacity. At higher voltages, there are often cases of elements boiling, and they become unusable.

Before you start charging an element, it is necessary to carry out its diagnostics, the meaning of which is to determine the ability of the element to withstand a certain load. To do this, first connect a voltmeter to the element and measure the residual voltage, which should not be lower than 1 V. (An element with a lower voltage is not suitable for regeneration.) Then the element is loaded by 1...2 seconds resistor 10 ohm, and if the element voltage drops by no more than 0.2 V, it is suitable for regeneration.

The electrical circuit of the charger shown in rice. 1(suggested), designed to charge six cells simultaneously ( G1...G6 type 373, 316, 332, 343 and others similar to them).

https://pandia.ru/text/77/496/images/image006_250.jpg" alt="Electric" width="439" height="222 src=">!}

Zener diode VD1 type KS119A limits the cell charge voltage. It can be replaced by a set of diodes connected in series - two silicon and one germanium - with a permissible current of at least 100 mA. Diodes VD2 And VD3- any silicon with the same permissible average current, for example KD102A, KD212A.

Capacitor capacity C1- from 3 to 5 µF for operating voltage not less than 16V. Switch circuit SA1 and control sockets X1, X2 for connecting a voltmeter. Resistor R1 - 10 Ohm and button SB1 serve for element diagnostics G1 and monitoring its condition before and after regeneration.

The normal state corresponds to a voltage of at least 1.4 V and its reduction when connecting the load by no more than 0.2 V.

The degree of charge of the element can also be judged by the brightness of the lamp. HL1. Before connecting the element, it glows at approximately half-incandescence. When a discharged element is connected, the brightness of the glow increases noticeably, and at the end of the charging cycle, connecting and disconnecting the element causes almost no change in brightness.

When recharging cells of the type STs-30, STs-21 and others (for wristwatches), it is necessary to connect a resistor in series with the element 300...500 Ohm. Battery cell type 336 and others are charged one by one. To access each of them you need to open the cardboard bottom of the battery.

plus" to "plus"). As diodes VD1, VD2 any with a working reverse voltage of at least 400 V.

To help the radio circle"

WITH A wide variety of household equipment (radios, tape recorders, electric players), measuring instruments, electronic watches and many other structures are powered by galvanic cells and batteries. Time passes, and the power source has to be replaced, sometimes throwing away elements and batteries that are still usable. Suitable because, like a car battery, they can be recharged and put back into service.

P The process of restoring the functionality of a galvanic power source is called regeneration; it was first discussed more than three decades ago. Practice has shown that not every element (or battery) is suitable for regeneration, but only those whose voltage, and therefore capacity, have not dropped below a certain level. For example, for a 3336 battery, such a limit can be considered a voltage of 2.4 V. A galvanic cell is subject to regeneration if its EMF is no more than 0.2 V higher than the voltage under load. Moreover, the load current during testing should be equal to approximately 5...10% of the rated capacity of the element.

WITH The diagram of the simplest device for testing the ability of an element (or battery) to regenerate is shown in Fig. 109. Voltmeter PV1 measures the EMF and voltage of the source being tested (it is connected to terminals XT1 and XT2 in the polarity indicated on the diagram), and push-button switches SB1 and SB2 set one or another discharge mode (load resistance).

TO As experiments show, elements (batteries) that operate at high load currents (children's toys, flashlights, portable tape recorders, etc.) are most successfully restored; sources that operate at low currents (portable radios, electromechanical alarm clocks) are worse. ).

R The story about the restoration of galvanic cells (batteries) should perhaps begin with the case when such a power source was stored for a long time and dried out. Then you need to make two holes with an awl or a thin nail in the top cardboard cover and the bitumen filling of the element and inject some water (preferably distilled) into one of the holes using a medical syringe. In this case, the displaced air will escape through the second hole. In addition, this hole will become a control hole - as soon as water appears in it, the syringe is removed.

P After the “injection,” the hole is sealed with a hot soldering iron or the flame of a lit match. After some time, and sometimes immediately, the element is ready for use.

A They act similarly with the battery, making an “injection” into each of its elements.

E If the element (battery) has lost its original capacity during operation, it is connected to a charger. And in order for the element to charge, you need to pass a very specific charging current through it and keep the element in this state for the required time. Typically, for batteries, the charging current is taken equal to a tenth of its capacity. The same ratio can be adopted for galvanic power supplies. Therefore, chargers differ somewhat from each other in circuit design: after all, each of them provides charging current for its “own” battery.

U device, the diagram of which is shown in Fig. 110, charges elements 332 and 316 and even small-sized batteries D-0.2. It provides a charging current of about 20 mA. The main part of the device is a rectifier assembled using diodes VD1 and VD2. The rectified voltage is smoothed out by filter C1R2C2 and supplied to terminals XT1 and XT2, to which the charging power source is connected. Zener diode VD3 protects capacitors from breakdown when the load is accidentally disconnected, resistor R1 limits the charging current.

R It is best to use resistor R1 of the PEV brand (vitrified, wire), but it can also be composed of four series-connected MLT-2 with a resistance of 2 kOhm (one of the resistors is 2.2 kOhm). The diodes can be any other, designed for a reverse voltage of at least 300 V and a rectified current of more than 50 mA, and a zener diode (except for the one indicated in the diagram) - D809, D814A, D814B. Capacitors - K50-6 or others. Clamps - any design. If there is no high-power quenching resistor R1 or MLT-2 resistors, an ordinary paper capacitor with a capacity of 0.2...0.25 μF for a rated voltage of at least 400 V is suitable instead.

D To charge elements 373, 343 and batteries 3336, another device is intended (Fig. 111), in which the quenching resistor (it should be of significantly higher power compared to the same resistor of the previous device) is replaced by a paper capacitor C1. A shunt resistor R1 is connected in parallel with the capacitor, allowing the capacitor to discharge after the device is turned off. Subsequent circuits of diodes, capacitors and resistors have the same purpose as in the previous device.

N Don’t be surprised that this charger is proposed to connect sources with different voltages - 1.5 and 4.5 V. Their charging current is different, so when you connect, say, element 373, due to an increase in the current through it, the voltage at the element’s terminals will drop until specified.

D So far we have been talking about charging galvanic cells and batteries with strictly direct current, that is, rectified current, “cleansed” of alternating voltage ripple. Somewhat better results are obtained when charging these power sources with so-called asymmetric alternating current, which has a positive direct component. The simplest source of such current is a half-wave rectifier using a diode, shunted by a constant resistor, and without filter capacitors. The rectifier is connected to the secondary winding of a step-down transformer with a voltage of 5...10V.

T when, at one half-cycle of the mains voltage, the current will flow through the diode and the charged element (or battery), and at the other, through the resistor and the same load. By changing the resistance of the resistor, you can select the ratio (asymmetry) between the constant component of the charging current and the effective value of its variable component within 5...25 (in practice, this ratio is maintained within 13...17).

IN The option with a shunt resistor has, unfortunately, low efficiency and another drawback - if the mains voltage is accidentally turned off (or the contact of the mains plug is broken), the power source will be discharged through the resistor and the secondary winding of the transformer.

B A more optimal option is with a shunt capacitor (Fig. 112). Its capacitance is such that at a frequency of 50 Hz the capacitive resistance of the capacitor is approximately 320 Ohms - it determines the asymmetry. In addition, the HL1 lamp is included in the charging target, which acts both as a charging current stabilizer and as an indicator of the degree of charge of the load - as the source G1 is charged, the brightness of the lamp decreases.

P The step-down transformer T1 is made with taps in the secondary winding. This is necessary to select the voltage supplied to the rectifier depending on the load charging current.

P When terminals 3-6 of the secondary winding are connected to the rectifier, the device is ready for charging - regeneration of batteries 3336 or elements 373, requiring a constant component of the charging current of 200 mA. If you apply voltage to the rectifier from pins 4-6, you can connect elements 343, 332, 316 to the charger. If the charging current of elements 373 or 343 turns out to be excessive, it is easy to reduce it by connecting pins 3-5 to the rectifier. In a word, by connecting certain terminals of the secondary winding to the rectifier, you can select the desired charging current.

E If you have at your disposal only transformers without taps in the secondary winding, you should be guided by the fact that the effective voltage value supplied to the rectifier (in other words, removed from the secondary winding of the transformer) should be 2.3...2.4 V per regenerated element. Therefore, when regenerating, for example, a 3336 battery, this voltage should be 6.9...7.2 V.

R It is advisable to carry out regeneration separately for each galvanic cell, but in some cases it is possible to connect two or three cells in series and connect the resulting battery to a charger. But this option is possible only with the same or similar degree of discharge of all elements. Otherwise, the “worst” (most discharged) element limits the current, which will affect the time and quality of regeneration.

IN the rectifier diode can be any low-voltage, allowing a current of up to 300 mA, an oxide capacitor - K50-6, a lamp - for a voltage of 3.5 or 6.3 V (MH 3.5-0.14, MH 6.3-0.3 ). The transformer is homemade, made on the basis of a unified output sound transformer TVZ-1-1. Its primary winding remains, and the secondary winding is modified - taps are made from it. To do this, 30 turns are unwinded (but not broken) from the secondary winding, a tap is made (pin 4), 26 turns are wound and a tap is made again (pin 5), the remaining 4 turns are wound and pin (6) is soldered to the end of the wire.

T The transformer can be made independently using a magnetic circuit Ш16Х24 or a similar cross-section. The network winding (pins 1-2) must contain 2400 turns of PEV-2 wire 0.15, the secondary - 70 (pins 3-4), 26 (pins 4-5) and 4 (pins 5-6) turns of PEV-2 wire 0.57.

IN During regeneration, the EMF of the element is periodically checked. As soon as it increases to 1.7...2.1 V and remains stable during the subsequent hour-long charging, regeneration is completed.

ABOUT b The efficiency of regeneration with asymmetric current can be judged by checking the energy parameters of the cell or battery: EMF and voltage, duration of discharge to a certain voltage (at the same load resistance) before and after charging.

5.5 Charger for voltaic cells

Let's consider the possibility of reusing galvanic cells and batteries. As is known, the greatest effect is achieved by charging with an asymmetric current with a ratio of charging and discharging currents of 10: 1.

The charger circuit is shown in Fig. 115. The pulse generator with adjustable duty cycle is made on logic elements DD1.1-DD1.3. The pulse repetition rate is about 100 Hz. A switch is assembled on transistors VT1 and VT2 that amplifies the generator current pulses. If the output of logic element DD1.3 has a low voltage, transistors VT1, VT2 are open, and a charging current flows through the battery connected to the XS1 sockets. When the voltage is high at the output of element DD1.3, both transistors are closed and battery GB1 is discharged through resistor R7. The variable resistor R1 changes within small limits the ratio of the durations of the open and closed states of the transistor VT2, i.e., the duty cycle of the asymmetric current pulses.

The K561LN2 chip can be replaced with K561LA7, K176LA7; transistor VT1 - any of the KT203, KT361, KT501, VT2 series - any of the KT815, KT817, KT3117, KT608 series. Diodes VD1, VD2 - D311, KD503, KD509, D223 with any letters.

Setting up the device consists of selecting resistors R6 and R7 according to the required values ​​of charging and discharging currents. The supply voltage is selected within bV in accordance with the total voltage of the charged elements. The charging current is selected based on the (6...10) hour charge mode. Pulse duty cycle

current is selected experimentally - depending on the type of charged elements.

I needed a charger for the battery Krona, the circuit was found at this address: http:///index. php? act=categories&CO...le&article=2573
But not only is the description of the circuit in non-Russian, but after assembly the circuit did not work. It turned out that there was a typo in the circuit; pins 3 and 6 of the timer were mixed up. Below is the corrected diagram and the signet for it:
http:///index. php? act=ST&f=59&t=17078&st=0#entry339479

https://pandia.ru/text/77/496/images/image013_229.gif" width="684" height="362">
The circuit is intended for installation in an industrial charger for batteries 7D-0.115 (that’s what it says on it) or “Nika”. You should not use it to restore Krona batteries, because...

the latter can “leak” and damage the device itself or lead to a fire.

break in." To do this, take a capacitor of the largest possible capacity (I used 150,000mkF), connect a resistance of 3-10 kOhm in parallel to it and connect it instead of the battery, observing the polarity. It turns out to be an imitation of a battery with a very small capacity. The LED begins to periodically light up and go out. In this form, it is advisable to leave the circuit for 1-2 hours. After the “break-in” is completed, the resistance connected in parallel with the capacitor is removed and a voltmeter (preferably digital) is connected in its place. With the trimmer resistor R2, the threshold for turning off the LED is set to 10.5 V. If you want After charging is completed, to maintain the battery capacity at about 100%, it is necessary to reduce the value of resistor R3 to 33 kOhm.

Details: capacitor C1 for a voltage of at least 250 V, preferably 400 V; Zener diode for voltage 12-15 V; the K561LN2 microcircuit can be replaced with 561LE5, 561LA7, changing the switching circuit accordingly; capacitor C2 for a voltage of 16V (when reducing its capacitance to 470 µF, it is advisable to include a 100-200 Ohm resistance in series with C1 to limit the current surge when the device is connected to the network); transistor KP303 with an initial drain current of 10 mA (letters: G, D, E) can be used with any one with similar parameters; LED - any of the AL307 series; resistors 0.125 W.

In the chip, 3 inverters remain unused. This makes it possible to assemble a second channel on them and install it all in a “Chinese” charger. You can also use them for sound or light indication of operating modes.

You can supplement the circuit for “training” and restoring old batteries (Fig. 2). In this case, resistor R3 (Fig. 1) must be replaced with a trimmer with a rating of at least 200 kOhm to set the lower limit of the circuit’s response voltage (7V). Here, using S1, select the charge/training operating mode (the diagram shows it in charge mode). This mode is especially useful for NiCd batteries, both those that have been in use for a long time and those that are completely new (3-4 training cycles allow them to reach full capacity). As an example, I will give a test of this mode with a 7D-0.125D battery (year of manufacture - 1991, year of commissioning - 1992, installed in an MP-12 multimeter with a current consumption of 1-2mA).

* - capacity measured before restoration. It was measured at a current of 0.5C (i.e., overestimated by 20 percent, which I do not consider a crime, due to the low current consumption of the multimeter, at which the capacity will be even greater).
** - the last recovery cycle was carried out using the “deep” discharge method and 3 cycles of regular training. This is where I ended the torment of this battery.
Source: shems.

Low-current chargers with transformerless mains power supply http:///document4979.html !!! The charger with mains power (Fig. 15.1) is intended for recharging STs-21 elements with a current of 2.5...3 mA (charging time hours) or RC-31 elements with a current of mA. The maximum value of the charging current is determined by the capacity of the quenching capacitor C1 and is 16 mA; it can be reduced by resistor R1. Like other similar mains-powered devices, this charger is not isolated from the mains supply, so extreme caution is required when working with it. Rice. 15.1. Charger circuit with mains power supply Rice. 15.2. Rectifier circuit for recharging cells and batteries The circuit proposed by E. Gumeley (Fig. 15.2) does not have a step-down transformer and is powered by 220 V AC mains. Capacitors C1 and C2 must withstand the voltage. They can be replaced with resistors with a total resistance of 24 kOhm and a power of at least 2 W. The circuit is intended for recharging batteries that are partially discharged, but not more than to a voltage of 1.1 6 per cell, since recharging using such a circuit involves reduction of only the positive electrode by oxidation of MnOOH to MnO2. The rectifier can be used to recharge elements and batteries such as KBS, Krona, etc. The output of the device is not isolated from the mains supply. The rectifier is designed to charge sealed disk and cylindrical nickel-cadmium batteries with a current of 12, 25 and 50 mA (Fig. 15.3). By changing the capacitance of the quenching capacitor, you can set the maximum current at the rectifier output. Increasing the capacitance of a capacitor by an integer number of times provides a proportional increase in current. Electrolytic capacitors are not allowed in the rectifier, since they do not work in alternating current circuits. Rice. 15.3. Rectifier circuit for charging nickel-cadmium batteries Rice. 15.4. Transformerless charger circuit The charger (Fig. 15.4) contains a rectifier with a quenching capacitor C1. A stable charging current through elements GB1, GB2 is provided by incandescent lamp EL1. At a charging voltage of 4...20 6, the charging current is maintained constant at 35 mA. It should be noted that to ensure such a charging current, the capacity of the quenching capacitor should not exceed 0.5 μF. The big disadvantage of the circuit is its direct connection to the electrical network. When working with the device, it is necessary to completely exclude the possibility of touching the circuit elements, especially when changing chargeable elements. To charge the battery of a rechargeable flashlight (three elements of 1.2... 1.4 6 each), a device is used (Fig. 15.5), which allows you to prevent overcharging. Rice. 15.5. Circuit diagram of a charger for a rechargeable flashlight battery with overcharge protection Zener diode VD5 type KS156 limits the maximum voltage on the battery. The HL1 LED extinguishes excess voltage and at the same time serves as an indicator of the end of charging - it begins to glow dimly. Separating capacitor C1 type K73-17 with a capacity of 0.47 μF provides a charging current of 30...35 mA; with a capacity of 0.22 μF - up to 15 mA. As diodes VD1 - VD4, you can use more affordable elements, for example, type KD102B. The automatic charger (Fig. 15.6) stops the battery charging process when the voltage at its terminals reaches 9.45 B. The device consists of a half-wave rectifier on diode VD1, an electronic switch on transistor VT1 and diode VD3, and a threshold device on thyristor VS1. While the battery is charging and the voltage on it is below the nominal value, thyristor VS1 is closed. As soon as the voltage on the battery increases to the nominal voltage, the thyristor opens. The signal lamp lights up and at the same time transistor VT1 closes. Battery charging stops. The triggering threshold of the machine depends on the resistance of resistor R4. Rice. 15.6. Diagram of an automatic charger for battery 7D-01 Set up the device with a connected battery and a DC control voltmeter. At a voltage of 9.45 V at the battery terminals, selecting resistor R4 achieves the ignition of the warning lamp. Resistors R1 and R2, which heat up during operation, can be replaced with a series chain of a quenching capacitor with a capacity of 0.22 (0.25) μF at 300 V and an Ohm resistor. The capacitor is connected instead of resistor R1, and between the point of its connection with the diode VD1 and the anode of the zener diode VD2, an additional diode D226B is connected (anode to the anode of the zener diode). Transformerless power supplies with a quenching capacitor make it possible to provide sufficiently high power and voltage to the load, however, they are not without one, but very significant drawback: their output is not electrically isolated from the supply network, and therefore working with such devices is associated with increased danger. It is quite original to solve the problem of creating a transformerless power source using a damping The capacitor succeeded, which used an optoelectronic voltage converter to decouple the input and output circuits (Fig. 15.7). Rice. 15.7. Diagram of an optoelectronic converter with mains power supply The converter can be used to power electronic-mechanical or electronic-quartz watches, serve as a backup for their standard power source - a battery or accumulator, and also be used to recharge them. A four-element optocoupler voltage converter based on optocoupler analogues (AL107B-FD256 pairs) is capable of providing an output voltage of the order of 0.5 V at a load current of up to 0.4...0.5 mA. To do this, the capacitance of capacitor C1, designed for a voltage of at least 400 V, must be at least 0.75... 1.0 μF. An analogue of the primary winding of a transformer is a chain of LED optocoupler pairs connected in series. A chain of series-connected photodiodes acts as an analogue of the secondary (output) winding of the transformer. They operate in photo-EMF generation mode. It is worth noting that the efficiency of the device is low, since the efficiency of the optocoupler rarely reaches 1%. The output voltage of the converter can be increased by increasing the number of optocoupler pairs in the chain. The output current of the device can be increased by connecting several optocoupler chains in parallel. Photodiodes are connected in parallel to storage capacitor C2. At first glance, it may seem that the capacitor will discharge to these photodiodes, since they are connected to the capacitor in the “direct” direction. However, this is not so: in order for a noticeable current to flow through the photodiodes, it is necessary that the voltage drop across its semiconductor junction be a fraction of a volt. It is easy to see that for a chain of several diodes connected in series, this requires a voltage that is also several times greater, i.e. several volts. Instead of diode optocouplers, discrete elements can be used: conventional LEDs and photodiodes. By adding a device powered by a battery, for example a Selga receiver, with a connector for connecting to a network charger and switch SA1 “Radio Receiver - Charge”, the 7D~0.125D battery can be recharged without removing it from the receiver body. The network storage device for industrial production was modified by N. Vashchenko (Fig. 15.8) using resistors R1, R2 and iodine VD1. Rice. 15.8. Charger circuit with mains power supply When the modified charger is connected to the receiver, the green light of LED HL2 (switch SA1 - - in the Charge position) indicates that the charging circuit is working, and when the charger is connected to the network, the red light of the additional LED HL1 indicates that the battery is charging. When there is a green glow and no red light, there is no voltage in the network. This mode of charging the 7D-0.125D battery is extremely undesirable, but where it is unavoidable, overcharge protection should be provided. To do this, a zener diode VD2 with a stabilization voltage of 9.9 6 at a current of 10 mA is connected in parallel to the battery. The battery needs to be recharged every 3...4 hours of operation of the receiver (at medium volume). Battery charge duration is 2...3 times longer. Resistor R4 is selected according to the minimum brightness of the HL2 LED. Instead of D810, it is permissible to use zener diodes D814B or D814G, their analogues, as well as chains KS133A+KS162A or 2xKS147A, selecting them for the specified voltage. To automatically charge backup or lighting batteries during a network outage, 220 6 is provided with a device (Fig. 15.9), which allows you to keep the batteries constantly charged. Rice. 15.9. Automatic charger circuit When there is a 220 V network voltage, the device is constantly connected in parallel to the battery and is a key voltage stabilizer with a stable output current. The charge current (I3) depends on the capacitance of capacitor C1 and at 10 μF is equal to 0.7 A. The current is selected from the condition: I3 (24 hours) > 2lntn, where ln is the consumption current, A; tn is the number of hours per day the consumer operates on batteries. If the charge current from this condition is greater than the maximum charging current for a particular battery, it must be replaced with a battery of higher capacity. When the charge current is more than 1 A, diodes VD1 - VD4 should be replaced with more powerful ones, and VD5 and VS1 should be installed on heat sinks and the resistance of resistor R4 should be proportionally adjusted. If the speed of switching to backup power is not relevant, for example, when lighting a room, the relay can be eliminated and a switch installed at the output. Setting up the device comes down to setting the final charging voltage on the battery with resistor R6 so that you do not have to add water to the electrolyte for a month, and its density corresponds to a charge level of at least 70% of the capacity. This voltage can be determined for a specific battery as follows. Charge the battery to full capacity in any way, let it stand for about 1 hour to equalize the potential on the electrodes. After this, measure the voltage at the terminals without load. This is the voltage that is set by resistor R6 with the battery disconnected from the device. Connect the battery to the device, and it is ready to use. Capacitor C1 is paper or metal-paper for a voltage of at least 400 V. Relay K1 is RPU, MKU-48 or similar for 220 V. LED HL1 indicates the end of charging, HL2 indicates the presence of charging current.

Many batteries do not allow discharge below a certain value: if you cross a certain limit, irreversible processes will occur in the battery, after which the power source will become unsuitable for further use. In this regard, the issue of protecting batteries from too deep discharge is very relevant.

The diagram of one of the devices designed to protect batteries from discharge below the permissible value is shown in Fig. 14.13. To control the supply voltage, a conventional zener diode VD1 or an avalanche transistor VT3 replacing it is used.

a set of "charging currents that do not depend on fluctuations in the input voltage, as well as the resistance of the charged element. At the load of transistor VT1, the voltage is stabilized. A certain portion of the voltage is removed from the sliders of a group of potentiometers connected in parallel and powered by a stable voltage and supplied to the bases of transistors VT2 - VT5 Using resistors R3, R5, R7, R9, the value of the limiting current through the transistors and, accordingly, through the charged elements is set.

set of stable charging currents

The circuit (Fig. 14.15) is designed for separate charging of up to six chemical current sources. You can simultaneously charge completely discharged batteries and those that need to be recharged after storage. The latter will never recharge if you stop charging at the same time as those that need to fully restore their capacity. Due to the technological variation in the production of batteries, each of them provides a different capacity even when combined into a battery, this especially applies to long-term batteries.

The battery connected to socket XS1 is charged by the emitter current of transistor VT1, proportional to the base current, which decreases exponentially. In this way, the battery is automatically charged in an optimal way.

The reference voltage is formed by an analogue of a low-voltage zener diode on elements VT7, VT8, VD1, VD2. Diodes VD1, VD2 are selected from a combination of silicon - germanium or both germanium. The criterion for correct selection is a voltage of 1.35... 1.4 V at the emitter of transistor VT1. The resistor in the base circuit of the transistor determines the initial charge current. The charger itself does not require constant monitoring during operation.

Low current chargers

https://pandia.ru/text/77/496/images/image027_51.jpg" alt="http://" width="300" height="158 src=">!}
Rice. 14.16. End of charge control circuit

It is based on the comparator DA1. The non-inverting input receives a voltage of 1.35 B from the adjustable resistor R1. Through the contacts of the SB1 button, voltage from the controlled battery is supplied to the inverting input. If, when you fix the SB1 button in the pressed position, the HL1 LED starts to light, then the battery has been charged to a nominal voltage of 1.35 V. Next, control the voltage on the next battery, etc.

An automatically shut-off charger based on a thyristor switch (Fig. 14.17) consists of a rectifier and a source of stabilized reference voltage. The reference voltage source is made using a zener diode VD6. Through a resistive divider (potentiometer R2), a stabilized voltage is supplied to the base of transistor VT2. A VD7 diode is connected to the emitter of this transistor by its anode, connected by its cathode to the battery being charged. As soon as the voltage on the battery rises above a predetermined level, transistors VT1 and VT2, as well as the thyristor through which the charging current flows, will turn off, interrupting the charging process.

It is worth noting that the thyristor is powered by rectified voltage pulses from the diode bridge VD1 - VD4. Filter capacitor C1, transistor circuit and voltage stabilizer are connected to the rectifier via diode VD5. The incandescent lamp indicates the charging process and, if necessary, limits the short circuit current in an emergency.

Chargers can also use a current stabilizer circuit. In Fig. Figure 14.18 shows a charger circuit based on the LM117 chip with charging current limited to 50 mA. The magnitude of this current can be easily changed using resistor R1.

https://pandia.ru/text/77/496/images/image029_50.jpg" alt="http://" width="250" height="95 src=">!}
Rice. 14.18. Charger circuit based on current stabilizer

https://pandia.ru/text/77/496/images/image031_42.jpg" alt="http://" width="300" height="191 src=">!}
Rice. 14.20. Charger circuit with charging current limitation

https://pandia.ru/text/77/496/images/image033_39.jpg" alt="http://" width="400" height="175 src=">!}
Rice. 14.22. Charger circuit with current stabilization

The device can use microcircuits of types SD1083, SD1084, ND1083 or ND1084.

The diagram of the foreign charger "VS-100" is shown in Fig. 14.23. The device allows you to simultaneously charge 3 pairs of Ni-Cd batteries. During the charging process, the HL1 LED lights up, then the HL1 LED begins to flash periodically. The constant lighting of LEDs HL1 and HL2 indicates the end of the charging process.

The VS-100 charger is not without its drawbacks. Charging the most common batteries with a capacity of 450 mAh with a current of 160 ... 180 mA turns out to be unacceptable. Not all batteries can withstand the accelerated charging mode, so O. Dolgov developed a more advanced charger, the diagram of which is shown in the following figure (Fig. 14.24).

The mains voltage, reduced by transformer T1 to 10 V, is rectified by diodes VD1 - VD4 and through the current-limiting resistor R2 and the composite transistor VT2, VT3 is supplied to the charging battery GB1. LED HL1 indicates the presence of charging current.

VS-100" for Ni-Cd batteries

https://pandia.ru/text/77/496/images/image036_31.jpg" alt="http://" width="400" height="180 src=">!}
Rice. 14.25. Current stabilizer circuit for charging Ni-Cd batteries

"planted" battery. As practice shows, to recharge a battery during long-term storage, a small current is required, about 0.1...0.3 A (for 6ST-55). If the stored battery is periodically, about once a month, put on such a recharge for 2...3 days , then you can be sure that it will be ready for use at any time, even after several years of such storage.

In Fig. Figure 16.6 shows a diagram of a “recharging” device - a transformerless power source that produces a constant voltage of 14.4 V at a current of up to 0.3 A. The source is built according to the circuit of a parametric stabilizer with capacitive ballast resistance. The voltage from the network is supplied to the bridge rectifier VD1 - VD4 through capacitor C1. At the output of the rectifier, a 14.4 V zener diode VD5 is switched on. Capacitor C1 limits the current to a value of no more than 0.3 A. Capacitor C2 smoothes out the ripples of the rectified voltage. The battery is connected in parallel with the zener diode VD5.

soft" charge with a low current. The value of this current is inversely dependent on the voltage on the battery, but in any case, even with a short circuit, does not exceed 0.3 A. When the battery is charged to a voltage of 14.4 V, the process stops.

When operating the device, you must follow safety rules when working with electrical installations.

A simple charger for charging car or tractor batteries (Fig. 16.7) has the advantage of increased safety in operation compared to transformerless analogues. However, its transformer is quite complex: it has many taps to regulate the charging current.

The charge current is adjusted by the slide switch S1 by changing the number of turns of the primary winding. The rectifier provides a charging current of 10... 15 A.

A portable device designed to charge lithium (lithium ion) batteries with pulsating current is shown in Fig. 16.9. The automated charger is made on the basis of a specialized microcircuit from MAXIM - MAX1679. The charger receives power from an AC adapter capable of delivering a voltage of 6 V at a current of up to 800 mA. To protect the circuit from incorrect connection, the VD1 diode is used - a Schottky diode - designed for a forward current of 1 A at a maximum reverse voltage of 30 V. The HL1 LED is designed to indicate the operation of the charger.

https://pandia.ru/text/77/496/images/image040_25.jpg" alt="http://" width="400" height="279 src=">!}
Rice. 16.9. Charger circuit for lithium ion batteries based on the MAX1679 chip

https://pandia.ru/text/77/496/images/image042_66.gif" width="402 height=268" height="268">

Rice. 1. Charging the battery with asymmetric current. Electrical circuit diagram

In Fig. Figure 1 shows a battery charging circuit with asymmetric current, designed to work with a 12 V battery and provides a pulse charging current of 5 A and a discharge current of 0.5 A. It is a current regulator assembled on transistors VT1...VT3. The device is powered by an alternating current voltage of 22 V (amplitude value 30 V). At the rated charging current, the voltage on a charged battery is 13...15 V (average voltage 14 V).

During one period of alternating voltage, one charging current pulse is formed (cut-off angle a = 60ْ). In the interval between charging pulses, a discharge pulse is formed through resistor R3, the resistance of which is selected according to the required amplitude of the discharge current. It must be taken into account that the total current of the charger should be 1.1 times the battery charging current, since when charging, resistor R3 is connected in parallel to the battery and current flows through it. When using an analog ammeter, it will indicate about one-third the amplitude of the charging current pulse. The circuit is protected against output short circuit.

The battery is charged until abundant gas evolution (boiling) occurs in all banks, and the voltage and density of the electrolyte remain constant for two hours in a row. This is a sign of the end of the charge. Then you should equalize the density of the electrolyte in all banks and continue charging for about 30 minutes to better mix the electrolyte.

When charging the battery, you should monitor the temperature of the electrolyte and not allow it to exceed: 45ْ C in temperate and cold zones and 50ْ C in warm and hot humid climate zones.

Since hydrogen is released when charging acid batteries, you should charge the batteries in well-ventilated areas, and you should not smoke or use open flame sources. The resulting explosive mixture has great destructive power.

(The gas released when the electrolyte boils carries droplets of acid, which, when they enter the respiratory system, onto the mucous membrane of the eyes, skin, corrode them, so it is better to charge batteries in the open air outside - U.A. 9 LAQ ).

Literature: 1. Batteries and Accumulators. Series “Information publication”.

Issue 1. “Science and Technology”, Kyiv, 1995, pp. 30...31.

2. Deordiev and care for them. Equipment, Kyiv, 1985

P. S. The topic is relevant for everyone who uses high-power autonomous power supply, for mobile (mobile) radio stations, participants in radio expeditions and “Field Days”. It is better to install transistors VT2 and VT3 on heat sinks with sufficient surface area. It is better to make powerful low-resistance resistors from copper wire, winding it around a frame made of non-flammable, refractory material. It is possible to manufacture such resistors from high-resistance wire or use powerful low-voltage incandescent lamps. Since the latter have a variable resistance, on the one hand, they can cause instability of the protection threshold; on the other hand, when connected in series, they will be (additional) current stabilizers (here: charging current).

For sealed batteries with gel electrolyte, along with a cyclic gentle charging mode with a constant current, they use a floating charging current mode at a constant voltage, in which case it is necessary to set the voltage to 2.23...2.3 V per battery cell, which in terms of for example, for a 12-volt battery it will be: 13.38...13.8 V. When the temperature changes from minus 30° C to plus 50° C, the charge voltage can change from 2.15 to 2.55 V per cell. At a temperature of 20ْ C when using a battery in buffer mode, the voltage on it should be in the range of 2.3...2.35 V per cell. Voltage fluctuation (for example, when changing the load on a combined power supply with a “buffer” battery) should not exceed plus/minus 30 mV per element. When charging voltages are greater than 2.4 V per cell, measures should be taken to limit the charging current to a maximum of 0.5 A per amp-hour of capacity.

When using a battery in a buffer with a voltage stabilizer, the voltage at the output of the latter should be selected so that it does not exceed the voltage of a freshly charged battery, for example, 14.2 V for a 12-volt battery, taking into account the voltage drop across the isolation diode (between the stabilizer and the battery), which should be selected with a margin for the maximum load current and battery charging current (unless the possibility of connecting a discharged battery is excluded).

The diode must have the maximum possible reverse and minimum possible forward resistance to ensure, respectively, minimal discharge of the battery through the stabilizer disconnected from the network and a minimum drop in the charging voltage when changing the load as indicated above. Powerful Schottky barrier diodes work well here.

The principles outlined above are, for the most part, acceptable for miniature non-acid batteries, but the voltages and currents are different.

A few words about the regeneration of galvanic cells.

Rice. 2. Charging galvanic cells with asymmetric current. Basic electrical diagram.

In [1], a simple scheme for charging galvanic cells with an asymmetric current is given, when two diodes are connected to the secondary winding of a step-down transformer according to a half-wave rectification circuit of positive and negative voltage. A two-watt resistor with a resistance of 13 Ohms is connected in series with one diode (for direct charging current), and in series with another, connected in the opposite polarity, the same resistor, but with a resistance of 100 Ohms, to provide the discharge current. Both circuits are connected to a galvanic cell or battery of them. (Fig. 2). By the magnitude of the voltage supplied to the input of the rectifiers or the value of the resistor values ​​in the available proportion, you can synchronously change the charge and discharge current of galvanic current sources. The ratio of charging current to discharge current is 10:1, the ratio of pulse duration is 1:2. As indicated in [1], the device allows you to activate watch batteries and old small batteries. Moreover, the charge of the former should be carried out with a current of no more than 2 mA and last no more than 5 hours.

At one time, I used the “floating” method of charging galvanic cells, which allowed me to operate three 9-volt sets of 316 “Prima” elements for a couple of years and, for a total of 4 years, when the elements combined into one “survived” from the three sets . The elements were taken new: literally two weeks after release they arrived at my place, a preliminary selection for identity was carried out and the operating procedure was thought out. The charging mode I selected provided charging current for 12...15 hours from a stabilized power supply with an output voltage of 9.6 V, i.e., 1.51 V per element (up to 1.52...1.53 V is possible). This mode prevents the elements from heating up when charging, which means that the elements do not dry out for a long time. The battery was operated in a CB radio station with an output power of up to 1 W (VIS-R). The elements were not stored in a discharged state; operation was carried out in a buffer (stabilizer plus battery) in stationary conditions and in field conditions, after returning from which, the battery (inside the station) was returned to its place again: to the stabilizer.

City youth scientific and practical conference

“SCIENTIFIC POTENTIAL OF THE CITY - XXI AGE"

SECTION “Electrical engineering, electromechanics and industrial automation”

Myazitov Rishat,

10th grade students

educational institution

Secondary education

School No. 22 in Syzran

Scientific supervisor: Antipova Natalya Yurievna

Physics teacher, Secondary School No. 22

Consultant: Antipova Natalya Yurievna

Physics teacher, Secondary School No. 22

Syzran 2010

Introduction________________________________________________________________ 3

Materials and methods of research_______________________________________________ 4

Regeneration of galvanic cells _____________________________________ 5

Diagnostics of elements ___________________________________________________ 5

Charger for Krona battery ___________________________________ 5

Research results _________________________________________________ 7

Conclusion ________________________________________________________________ 8

Applications ____________________________________________________________ 9

Used literature _________________________________________________ 12

Introduction

The issue of reusing galvanic batteries of the manganese-zinc (Zn) system has long been of concern to electronics enthusiasts. The idea of ​​restoring discharged galvanic cells is not new. Over the years, a wide variety of methods have been used to “revitalize” elements: squirting with water, boiling, deforming a glass, charging with various currents. In some cases, a surge in electromotive force (EMF) was observed, followed by its rapid decay. The elements did not reach the expected capacity, and sometimes they leaked and even exploded.

Currently, the problem associated with the discharge of galvanic cells is very relevant, because they are used in many devices that surround us. For example: remote controls, children's electronic toys, all kinds of communication and communications equipment (mobile phones, walkie-talkies, etc.), watches, portable audio players, etc. Also, due to the global financial crisis, you can easily save on batteries by restoring the functionality of discharged cells by charging them.

As you already understood, we propose to design a charger for a Krona battery.

Why exactly “Krona” you ask. But simply because they are the most expensive of all galvanic elements, and accordingly the savings will be significant.

During our work, we used information and diagrams presented by V. Bogomolov and Alimov, located on the links:

respectively.

Currently, galvanic cells are restored using special chargers (Appendix 1). It has been practically established that the most common manganese-zinc cup cells and batteries, such as 3336L (KBS-L-0.5), 3336X (KBS-X-0.7), 373, 336 (Appendix 2) are better than others for regeneration. .

Materials and methods of research.

The purpose of the research in our work is a comprehensive, reliable study of various types of galvanic cells, batteries, their use in various devices, the maximum operating time before discharge and possible ways to restore these elements using chargers. After studying the material, we decided to design a charger on our own and find out its functionality.

In our work we used the following materials:

A step-down transformer

Diode bridge

Capacitor

Voltmeter

Connecting wires

To achieve the goal in our work, we used empirical methods: observation, measuring the voltage on a discharged battery, comparing the measured value with the maximum value. Voltage measurements were carried out using analog and digital voltmeters.

The experimental-theoretical method allowed us to study the theory about the purpose and operating principles of a transformer, diode, capacitor and apply the theory for a practical purpose - we designed a charger.

Regeneration of galvanic cells

The charging process must be carried out at a very specific voltage - 10-12 V. At a lower voltage, regeneration is very delayed; the cells, even after 8 ... 10 hours of charging, do not reach half their capacity. At higher voltages, there are often cases of elements boiling, and they become unusable.

To power small-sized transistor radios, 7D-0.1 type batteries are often used, which are secondary sources of direct current. The initial voltage of a normally charged 7D-0.1 battery is about 9 V. The battery is considered discharged if its voltage drops to 6.8-7 V.

In order for the battery to become functional again, it must be charged. To do this, a current is passed through it for 12-15 hours, the strength of which is numerically equal to approximately a tenth of its electrical capacity. When charging a battery, its electrodes are connected to the same poles of a direct current source.

Diagnostics of elements.

Before regenerating galvanic cells, it is necessary to diagnose them and find out which elements can be restored and which are not suitable for regeneration. The point of diagnosing elements is to determine the ability of an element to “hold” a certain load, for example, in the form of a 10 Ohm resistor. To do this, first connect a voltmeter to the element and measure the residual voltage, which should not be lower than 1V (an element with a lower voltage is definitely unsuitable for regeneration). Then the element is loaded for 1...2s. the specified resistor. If the cell voltage drops by no more than 0.2V, it is suitable for regeneration. Diagnostics are carried out using a voltmeter.

Charger for Krona battery.

The issue of reusing galvanic batteries of the manganese-zinc (Zn) system has long been of concern to electronics enthusiasts and is still relevant today, especially in the context of the global financial crisis, when anyone who uses galvanic cells can easily save on them by restoring the functionality of discharged elements by charging.

As you already understood, in this work we will talk about the manufacture of a charger for galvanic cells, namely for a 9 V “krone” battery. Why exactly the crown will make you wonder. But simply because it is the most expensive of all galvanic elements and is widely used in various radio receivers and radio-controlled toys (Appendix 4).

Battery "Krona" (also PP3, E-Block) - standard size . The name comes from the brand produced in carbon-manganese batteries of this standard size "Krona VTs".

Specifications: dimensions: 48.5 mm × 26.5 mm ×17.5 mm., n 9 ., typical 625 alkaline battery .(Appendix 3).

The Krona battery has a capacity (according to the passport) of 0.5 Ah, in reality (due to self-discharge during storage) it is two to three times less. The internal resistance of the Krona battery (about) is 34 Ohms.

Design

Alimov I. Regeneration of galvanic elements. - Radio. 1972, No. 6

Ivanov B.S. Electronic homemade products. - M.: Education, 1993

Handbook of amateur radio designer. - M.: Energia, 1973

Safonov O.A. Handbook for school radio amateurs. - M.: Education, 1970