Charger for NiCd and NiMH batteries. Nickel-cadmium batteries: device, restoration. How to charge a nickel-cadmium battery? Charger circuit for nickel cadmium

Today we will tell you how to properly charge nickel-cadmium batteries.

Classic charge- this is a charge with a stabilized current of 10% of the capacity indicated on the battery for 14 hours. Thus, for a cell to be charged 100%, it needs to be given 140% of its capacity. Let's look at the example of the battery shown in the picture above. The battery says: 600 mAh (translated means 600 mAh miles Ampere hours) to charge it, you need to supply a current equal to 600/10 = 60 miles Ampere for 14 hours. Similarly, to charge a 1200 mAh battery - 120 mA for 14 hours.

Accelerated charging of Ni-Cd batteries— charge with a stabilized current of 30% -40% of the capacity indicated on the battery. In this case, the condition of reporting 140% capacity is maintained. Let's consider the example of a battery with a capacity of 1000mAh: we need to report 140% of the capacity, that is, 1000mAh x 140%= 1400mAh. Let's say the charge current is chosen to be 35% of the capacity, which is equal to 350mA, to get the charging time we take 1400 mAh / 350mA = 4 hours.

Pulse charge Ni-Cd batteries This type of charge is used to partially restore the capacitive characteristics of the battery and extend its service life. The essence of pulse charging of a nickel-cadmium battery is alternating charge pulses with short-term load connection (discharge pulses).

The discharge current is selected within 5-10% of the battery capacity. The ratio of the length of the discharge pulse to the charge pulse is about 1:10. For example: 20ms discharge pulse, 200ms charge pulse. All of the above types of charge are valid, but during operation the battery loses its useful capacity. The most correct way to determine the end of the charge is method of measuring the change in voltage across an element. (delta V)

Charge Ni-Cd batteries by delta V This is the most progressive and accurate type of battery charging, preventing it from overcharging. Most modern chargers are based on this principle of operation, in combination with monitoring the temperature of the element. So what is delta V? During the charging process of the battery, the voltage at its terminals increases and reaches an upper peak at the moment when the battery has received the maximum possible charge. After passing the point of maximum stress, it begins to fall. This process is called “delta V”. For Ni-Cd batteries, the value of delta V at the end of the charge is about 10 mV, the same parameter y is 3-7 mV. At the moment the charge ends, a rapid increase in the temperature of the element is also observed. Modern specialized microcircuits for charging Ni-Cd batteries such as MAX712 or a cheaper, but no less smart analogue microcircuit MC33340, are able to monitor these characteristics (voltage, temperature). However, it must be taken into account that overcharging with a current above 10-20% of the capacity can lead to a battery explosion. Thus, if there is no particular need for fast charging, a classic charger is quite suitable, i.e. providing a stable current of 10% of the rated capacity.

When using nickel-cadmium batteries, before charging them, they must be discharged to a voltage of 0.8 - 1 V per cell. At first I used a simple method - I loaded it with an incandescent lamp or a one-watt resistor, but there were cases when I forgot about the battery and it discharged to zero.
A simple device was made to discharge nickel-cadmium batteries.

The discharge current is set by the resistance of resistor R6, and for a battery with a voltage of 3.7 V and a capacity of 700 mAh, this is approximately 70 mA. The voltage threshold to which the battery is discharged is set by resistor R2. The discharge process is indicated by the HL1 LED. When the specified voltage is reached, transistor VT1 closes, reducing the discharge current to 3 - 5 mA, and the HL1 LED goes out. To set the threshold, you need to connect the device to the power supply and move the resistor R2 to a position at which the HL1 LED goes out.

Transistor VT1 - low-power, germanium, zener diode VD1 for stabilization voltage 2 - 3.3 V, for example KS130, KS133, KS433.

The converter operates from 3 to 1.8 V, while consuming 150 mA. Below 1.8 V (0.9 V for each battery), generation stops, the current drops to 10 - 15 mA and depends on the resistance of resistor R1, LEDs HL1 and HL2 go out, well, that’s all, you can charge the batteries.

If you need to discharge one battery, then a germanium diode VD1 should be used, for example D9, D18.
Transistor VT1 is silicon, with a collector-emitter saturation voltage of 0.5 - 0.8 V and with a constant collector current of at least 1 A, for example KT815, KT817, KT630, KT831.
Transformer T1 is wound on a ferrite ring with an outer diameter of 10 mm with a permeability of 1000 - 2000, contains two windings - 30 turns in the base circuit and 50 turns in the collector circuit, with a wire with a diameter of 0.15 mm. If the converter does not work when you first turn it on, you need to swap the terminals of one of the windings of transformer T1.

This time we will talk about designing a simple USB charger for Ni-Cd and Ni-Mh batteries.

The circuit of a fairly good charger is simple and can be implemented with a budget of only 20 rubles. This is already cheaper than any Chinese charger. The heart of our charger is the well-known LM317 linear stabilizer chip.

The input of the circuit is supplied with a voltage of 5 V from any USB port.

The microcircuit stabilizes the voltage to 1.5 V. This is the voltage of a fully charged Ni-Mh battery.

And the device works very simply. The battery will be charged with a voltage of 1.5-1.6 Volts from the microcircuit. Resistor R1, acting as a current sensor, simultaneously limits the charging current. By selecting it, the current can be reduced or increased.

When a battery is connected to the output of the circuit, a voltage drop is formed across resistor R1. It is enough to trigger a transistor, the collector circuit of which has an LED connected to it. The latter lights up and will go out as the battery charges until it turns off completely. This will happen at the end of the charging process.

Thus, the diode lights up when the battery is charging and goes out when the latter is fully charged. At the same time, as the battery charges, the current will decrease, and at the end its value will be 0.

It follows from this that overcharging and failure of the battery is impossible.

The LM317 chip operates in linear mode, so a small heat sink will not hurt. Although at a current of 300 mA the heating of the microcircuit is within normal limits. It is advisable to select an LED with a minimum operating voltage. Color is absolutely not important. Instead of BC337, it is allowed to use any low-power reverse conduction transistor, even on KT315. The desired power of resistor R1 is 0.5-1 Watt. All remaining resistors are 0.25 and even 0.125 Watts. Since the voltage range is very narrow, even resistor errors can affect the operation of the circuit. Therefore, it is strongly recommended to replace resistor R2 with a multi-turn resistor of 100 Ohms.

With its help, you can very accurately adjust the desired output voltage.

First you need to find all the necessary components, as well as a slot for batteries.

The device can charge batteries of almost any standard if you adapt the appropriate slot. When assembling, you do not need to use a printed circuit board. Installation is done using a hinged method. The components are glued under the battery slot and filled with hot glue, since the circuit is very reliable in operation.

The assembled device looks something like this:

But it can look much better.

You just need to choose an LED with the lowest possible glow voltage, otherwise it may not light up at all. This scheme can charge several batteries, but it is recommended to use it only to charge one.

Today, one of the most popular types of energy replenishment for household appliances is nickel-cadmium batteries. This is a fairly easy-to-use device that, if handled correctly, will last a fairly long period of time. How to properly handle nickel-cadmium batteries should be considered in more detail.

general characteristics

The nickel-cadmium battery is designed in such a way that with low internal resistance it can deliver a fairly large current. Such batteries can withstand even short circuits.

Batteries of the presented type can easily withstand long-term loads. When the ambient temperature drops, their performance remains virtually unchanged.

Nickel-cadmium batteries are inferior to other types in capacity. However, their high efficiency makes batteries one of the most popular and in demand in the field of portable technology.

For devices with electric motors that consume high currents, the use of chargers such as nickel-cadmium batteries is simply irreplaceable.

The discharge currents at which they are used are in the range of 20-40 A. The maximum load for NiCd batteries is 70 A.

Advantages

The presented devices have a number of advantages. They are capable of operating in a wide range of discharge and charge currents, as well as temperatures.

Nickel-cadmium batteries can be charged at low temperatures due to their high load capacity. They are not picky about the type of tightening device. This is a significant advantage. It makes the device stand out from the mass of other varieties, since the nickel-cadmium battery can be charged in any conditions. It is resistant to mechanical stress and fireproof. Nickel-cadmium batteries have more than 1000 charge cycles and have the ability to recover after a decrease in capacity.

Low cost along with the listed advantages make NiCd batteries very popular.

Flaws

The nickel-cadmium battery design also has a number of disadvantages. The main one is the “memory effect”.

Over the course of several charge-discharge cycles, the structure of the electrode surface changes. In this case, chemical compounds are formed in the separator, which will subsequently interfere with the discharge of low currents. This leads to the source remembering its incomplete discharge.

The further you charge nickel-cadmium batteries, the more they will lose their efficiency. The source will have less and less capacity.

A disadvantage is also the high self-discharge during the first day, up to 10% after charging. Large dimensions can also be considered a disadvantage.

Charger

To understand how to charge nickel-cadmium batteries, you should consider a number of features of this process.

Fast charging mode for the presented power sources is preferable to slow charging. Pulse replenishment of capacity is better for them than direct current.

It is recommended to restore the device. Nickel-cadmium batteries require this. Manufacturers of the corresponding devices have taken into account how to charge them using this method. Reversible charging speeds up the process due to the recombination of gases released during the process.

The presented technique for restoring such batteries allows increasing the service life by up to 15%. How to charge a nickel-cadmium battery? There is a whole technology. To increase efficiency, some users use fast charging followed by refueling with weak currents. This allows the battery to be filled more tightly.

Storage and disposal

The batteries shown should be stored in a discharged state. There are chargers that have a discharge function. If there is none, before storage, nickel-cadmium batteries are emptied using an incandescent lamp with a permissible current of 3-20 A. The battery is connected to it and wait until the spiral begins to turn red.

This procedure will allow you to store the device for quite a long time. Moreover, environmental conditions and temperature changes will not have an impact on the device.

If you need to dispose of this type of battery, you should take it to a special collection point for such devices. All developed countries have them. This is due to the presence of cadmium in the battery. Its toxicity is comparable to mercury.

Understanding the technology of how to charge a nickel-cadmium battery, store it and dispose of it, you can have no doubt about the safety and durability of this power source. It will not harm the environment and human health if batteries are disposed of responsibly.

Recovery

Nickel-cadmium batteries are the only type of such devices that require restoration.

Periodic discharge-charge cycle will increase the life of the batteries. This should not be done too often, but from time to time it is simply necessary.

There are two types of devices for recovery. The first is called a reverse pulse charger with different duration times. This is a very effective device, but complex and expensive. Restoring nickel-cadmium batteries can be done with a simpler device. It performs a discharge-charge cycle automatically. This device is cheaper, more convenient and allows you to charge 2-4 batteries at once.

To carry out the process, you need to insert batteries into the equipment cassette. The number of batteries is set using the switch. Plugging the device into the network will activate the indicator. Red indicates charging and yellow indicates discharging. Green light indicating process termination. Batteries must be discharged forcibly. To do this, you need to switch a certain lever on the device. After the discharge is completed, the device will continue the charging process automatically.

Having become familiar with the basic characteristics of a power source such as nickel-cadmium batteries, you can use them correctly. By following the manufacturer's instructions and regularly reconditioning your batteries, you can significantly extend their life. By correctly disposing of the presented device, it will be quite simple to protect yourself, other people and the environment as a whole from the toxic effects of cadmium.

To calculate the charging time of a nickel metal hydride (Ni-MH) battery, you can use the following simplified formula:

Charging time (h) = Battery capacity (mAh) / Charger current (mA)

Let's say we have a Ni-MH battery with a capacity of 2000mAh, let's assume the charging current in our homemade charger is 500mA. We divide the battery capacity by the charging current and get 2000/500=4 hours!

Rules that are advisable to follow for long-term operation of a nickel-metal hydride (Ni-MH) battery:
Store Ni-MH batteries with a low charge level (30 - 50% of its capacity)
Nickel-Metal Hydride batteries are sensitive to heat, so never overload them, otherwise the Ni-MH battery's ability to hold and release its accumulated charge will sharply decrease.
Ni-MH batteries can be trained, but not necessarily. Four charge/discharge cycles in a good charger allows you to achieve maximum capacity, which is lost during battery storage.
After discharging or charging, give the hybrid some time to cool to room temperature. Charging Ni-MH batteries at temperatures below 5 or above 50 degrees can significantly damage their health.
If it becomes necessary to discharge a Ni-MH battery, do not discharge it below the level of 0.9V for each cell
If you constantly use the same battery of batteries in any device in recharging mode, then sometimes it is advisable to discharge each battery from the assembly to a level of 0.9V and charge it fully in an external charger.

For those who are not very well versed in radio electronics and are taking their first steps in this direction, I recommend assembling such a simple memory circuit, using just one bipolar transistor. Depending on the selected resistance value R2, the charging current will change and, in principle, charge a variety of batteries, even lithium ones.

R1 = 120 Ohm, R2 = See the table on the diagram, C1 = 220 uF 35V, D1 = 1N4007, D2 = almost any LED, Q1 - BD135 transistor

The circuit is ideal for use from the vehicle’s on-board network or from any power supply with an output voltage of 6-12 volts. It can be used to charge mobile phones, various electronic toys, tablets, MP3s, etc. The circuit is quite universal, since we select the charging current. A lit LED indicates that charging is in progress.

The table above indicates the minimum and maximum supply voltage of the charger. For example, to charge a 6V battery, the minimum voltage required is 12V. It is recommended to charge the battery with a current that is 10 times lower than the battery capacity, and it will take about 15 hours to charge it. If you double the charging current, you can charge the battery twice as fast and this will not damage the battery. The transistor must be mounted on a heatsink.

If you use various devices that still use AA batteries, then you have to change them often, for example, in a metal detector or GPS-GLONAS tourist navigator eTrex. But there is a solution to this problem: replacing conventional batteries with nickel AA batteries. This is where you need to charge AA batteries

The bipolar transistor and LED HL1 are the basis of the DC source circuit. The forward voltage of the LED is about 1.5 volts minus the voltage of the emitter junction of transistor VT1 (0.6 V) follows through a resistor with a nominal value of 6.8 Ohms or 15 Ohms, depending on the position of the SA1 toggle switch. When choosing a resistance of 15 ohms in the emitter circuit, the charging current will be about 60 mA, and with a resistance of 6.8 ohms the current will be 130 mA. This is quite enough to charge a nickel-cadmium battery with a capacity of 600 mAh in 14 hours or 5 hours, depending on the resistor.

A comparator on the LM393 chip is used to automatically turn off the memory. Its inverse input is set to 2.9 volts using a trimmer, and its direct input monitors the battery voltage.

During the charging process of a nickel-cadmium battery, the internal output transistor LM393 is open and, therefore, VT1 is also open. Once the battery is 80% charged or more, the voltage at the battery terminals will be above 1.45 volts. The voltage at the non-inverting input DD2 will become higher than the reference voltage at the inverting input and at the output of the comparator the signal will change to the opposite one, transistor VT1 will turn off, turning off the current source.

In order to prevent switching of the comparator in the threshold voltage range, a 0.1 µF capacitor was introduced into the design, creating feedback between the output and the inverting input of the microcircuit.

Four NAND gates DD1 are used to construct two generators with different frequencies. When the signals from them are connected, a tone signal appears, which is sent to the piezoelectric element at the moment when the battery charge is complete.

This circuit, made using 4 bipolar transistors, is primarily used for charging 12 volt Ni-Cd batteries. In addition, you can charge the batteries using 6 And 9 volts, but you will have to reduce the power of the device. The built-in current regulator regulates charging current up to four amps. When it reaches its maximum, the voltage across resistance R1 is 0.7V, so it opens transistor Q1. At this point in time, transistor Q2 is open and shunts the base of Q3 to ground, which leads to a shift in the mode of Q4, through which charging occurs. This is how the charging current is adjusted. When charging batteries with a low voltage level, excess charger voltage will drop to Q4.

The primary winding of the transformer is typical at 230 volts, the voltage of the secondary winding should be about 30 volts, with a current of 3 amperes. The diode bridge was assembled using four 1N5400 diodes; Fuse F1 for current 500 mA. Resistor R1 is difficult to find due to its non-standard resistance; it can be replaced with a resistance of 0.3 ohms each. The circuit can be supplemented with a filter capacitor and reverse polarity protection.

The charger described in the article is intended primarily for charging Ni-MH nickel batteries. It is based on a specialized LT4060 charge control microassembly. The circuit provided below is quite powerful and efficient; it is used to quickly (about an hour) charge a Ni-MH battery.