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We charge and use NiMH batteries correctly. Charger for NiCd and NiMH batteries Charger for ni cd battery circuits

B Most people who use batteries in their portable equipment know firsthand that this is a very fastidious power source, especially when it comes to nickel-metal hydride batteries (hereinafter referred to as NiMH)

These batteries have a limited lifespan both in time and in the number of discharge-charge cycles. The charger with all the mechanisms involved in this process also plays an important role.

B Most users of NiMH batteries are not aware of the intricacies of working with these batteries and are often disappointed in their use, not suspecting that the short life and low capacity are the result of improper use of the battery

The chargers that are included in the basic kit (see photo below) are, so to speak, “night lights,” i.e. they have the simplest circuit without stabilization, without shutdown function, discharge function, temperature control, delta shutdown, etc.

Actually, until recently, I only used such chargers, which created nothing but trouble for me when using batteries. Service life was minimal

So I decided to search online for chargers at auctions. Basically there were “night lights”, as well as modern intelligent NiMH chargers, microprocessor Chinese devices with all the necessary functions, but their price of 1500-3000 rubles did not suit me and by chance I came across a very old German charger Conrad VC4+1 for NiCd and NiMH + 1 crown 9v

IN There is no information on this charger on the Internet, only rare links to pages from German auctions.

Without thinking for a long time, I decided to buy this lot and after 2 weeks I had this charger in my hands. The price of the lot was 370 rubles and 250 rubles delivery, a total of 620 rubles for an ancient German charger with unknown qualities

Conrad VC4+1 Specifications and Features

After a short observation with a multimeter, as well as searching on the Internet, studying the inscriptions on the back cover of the device, I can say the following:

– charging current adjustable from 15 mA to 4000 mA
– two charging modes: “fast 85 minutes with a current of 1C” and “drip current of 0.1C”
– automatic discharge before charging up to 0.9V
– temperature sensor on the positive contact of the device
– automatic shutdown with subsequent charge support
– charging with pulsed current and pulses
– socket for charging batteries of the “crown” type
– type of batteries NiCd and NiMH, sizes from AAA to D size
– preliminary drip charging of a completely dead battery
– four independent channels

This is what the original charger looks like, which I bought at an auction, I really wanted to hold it in my hands and use such an interesting device

I haven’t figured out the delta shutdown and the operation of the temperature sensor yet. Below I want to provide photos of the charger boards

As you can see, a hand with a soldering iron had already looked in here; apparently, the charger was under repair. Basically, as I understand it, the power points of the device were simply soldered

German technologies were already available to everyone a dozen years ago and people used fairly smart chargers. As you can see and the diagrams, this is far from a night light

I am very pleased with the purchase and consider myself very lucky. This is a very rare charger in Russia, very old, but has functionality that is quite enough to keep your batteries in perfect condition.

G I consider the main advantages to be the ability to regulate the charging current from 15 mA to 4000 mA, as well as auto shutdown after 16 hours or 85 minutes (I did not notice a shutdown by voltage or delta) and support for full charge with pulses with a frequency of 1 in 20 seconds.

If anyone suddenly wants to buy such a charger for themselves, try searching on German online auctions. In Germany, this charge was quite common and well known.

Recently, smart chargers for NiMH batteries from LaCrosse, models bc-900, BC 1000 and technoline bc-700, have appeared on the market, as well as Chinese counterfeits and parodies. Such chargers differ both in appearance and in their operating principle and, of course, functionality. The price of smart chargers still remains high for the average user - 1500-3000 rubles, depending on the model and manufacturer


These devices promise to carry out all the necessary measures to ensure that NiMH serves its owner for a long time and faithfully, here is, for example, a list of features of the most expensive and functional models

TEST– full charge of the battery, followed by a full discharge to determine the actual capacity (indication on the screen), then full charge of the batteries
CHARGE– independent charge of each channel with a selected current (200/500/700/1000 mA)
DISCHARGE– battery discharge (adjustable) to reduce memory effect
TRAINING– up to 20 charge/discharge cycles until the battery capacity is fully restored

Works with all NiCd and NiMH “AA” and “AAA” batteries
LCD screen shows information for each battery separately
Can charge “AA” and “AAA” size batteries simultaneously
Detects bad batteries
Battery overheat protection
Possibility to select the charging current power for each channel
Automatically switches to trickle charging when charging is complete to ensure maximum battery capacity
Charging automatically starts at 200mA (optimal for extending battery life)

TO As you can see, the functionality really differs significantly from conventional “night lights,” but the next question arises: is such a smart charger worth $100?

Personally, since I already bought a Conrad VC4+1 and loved this charger for its antique charm and originality, now I will refuse to buy a LaCrosse, which in principle I do not regret. Because Many people don’t like the charging of the LaCrosse - for example, the rough regulation of the charge current.

During the operation of rechargeable batteries, it is recommended to periodically monitor their electrical capacity, measured in ampere-hours (Ah). To determine this parameter, it is necessary to discharge a fully charged battery with a stable current and record the time after which its voltage decreases to a predetermined value. To assess the condition of the battery more fully, it is necessary to know its capacity at different values ​​of discharge current.

H To measure the capacity of my batteries, I use a voltmeter that is connected in parallel with a resistance that is the load on the battery. I choose the resistance according to the average current of the consumer in which the battery is planned to be used - this is a very important point for calculating the capacity, since under different conditions of power consumption - the capacity of the batteries varies greatly. Thus, I take a fully charged battery, load it with the current I need and observe when the voltage on the battery under load drops to 1 - 0.9 volts, then I make a calculation by multiplying the discharge current by time. For example, the battery was discharged with a current of 500 mA for 2 hours, which means the battery capacity is 1000 mAh

If I would like to comment on your comments, I would like to hear feedback from owners of smart chargers, share your experience of using them, what disadvantages do they have?

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.




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.

This charger can be used to charge both nickel-cadmium and nickel-metal hydride batteries. If you have a li-ion battery, then you probably need it.

Description of the charger operation for nickel-cadmium and nickel-metal hydride batteries

The circuit does not provide fast but effective charging since the charge is carried out with a standard current - one tenth of the battery capacity in combination with a charging time of 10 to 14 hours, without the risk of overcharging. If you are sure that the battery is only half discharged, then you can fully charge it in about 6...7 hours.

AA size batteries have a capacity of 1500 to 1800 mAh (milliamp-hour), so the charging current should be between 150 and 180 mA. If you want to charge multiple NiCad batteries at once, simply connecting them in series will result in the same charging current flowing through the entire stack of batteries, charging them simultaneously.

The question now is how to get us a constant current of 180 mA. The most elegant and accurate solution would be to use a current source. This role can be played by a current source connected according to the circuit. The LM317 microcircuit is quite well-known and adjustments are made by selecting the resistance of the resistor, which is connected to the OUT and ADJ pins.

In our case (for 0.18 A), the resistance will be 6.94 Ohms (1.25/0.18) = 6.94 Ohms. This value can be obtained from several series-parallel connected resistors, but it is easier to take a close standard value of 6.8 Ohms.

To get a current of 180 mA you need some voltage. The maximum voltage when charging a nickel-cadmium battery is 1.5 V, and the current source required is about 3 V. If you charge only one battery, the supply voltage will be 4.5 V.

If you are charging several NiCd batteries at once, you need to multiply 1.5 V by the number of batteries plus 3 V. For four batteries, this would be a supply voltage of 9 V. If the voltage is too low, the charging current will be weak.

For more than 4 years it has served me faithfully homemade charger for charging “aa” and “aaa” batteries (Ni-Mh, Ni-Ca) with a discharge function battery to a fixed voltage value (1 Volt). The battery discharge unit was created for the possibility of carrying out CTC(Control-training cycle), to put it simply: to restore battery capacity battered by incorrect Chinese chargers with a sequential charging formula of 2 or 4 batteries. As you know, this charging method shortens the life of batteries if they are not restored in time.







Charger Specifications:

  • Number of independent charging channels: 4
  • Number of independent discharge channels: 4
  • Charge current: 250 (mA)
  • Discharge current 140 (mA)
  • Discharge 1 cut-off voltage (V)
  • Indication: LED

The charger was not assembled for an exhibition, but what is called from improvised means, that is, the surrounding goods were disposed of, which would be a pity to throw away and there was no particular reason to store.

What can you use to make your own charger for “AA” and “AAA” batteries:

  • CD-Rom case
  • Power transformer from the radio (rewind)
  • Field effect transistors from motherboards and HDD boards
  • Other components were either bought or bitten out :)

As already noted, charging consists of several nodes that can live completely autonomously from each other. That is, you can work with 8 batteries at the same time: charge from 1 to 4 + discharge from 1 to 4. The photo shows that the battery cassettes are installed under the “AA” form factor in the common people’s “pen-type batteries”; if you need to work with “mini-pen-type batteries” “AAA”, it is enough to place a small caliber nut under the negative terminal. If desired, you can duplicate it with holders for size “aaa”. The presence of a battery in the holder is indicated by an LED (the flow of current is monitored).

Charge block

Charging is carried out with a stabilized current, each channel has its own current stabilizer. In order for the charge current to remain constant when connecting both 1 and 2, 3, 4 batteries, a parametric voltage stabilizer is installed in front of the current stabilizers. Naturally, the efficiency of this stabilizer is not high and you will need to install all the transistors on the heat sink. Plan the ventilation of the case and the size of the radiator in advance, taking into account that in a closed case the temperature on the radiator will be higher than in a disassembled state. You can upgrade the circuit by introducing the ability to select the charge current. To do this, the circuit must be supplemented with one switch and one resistor for each channel, which will increase the base current of the transistor and, accordingly, increase the charge current passing through the transistor into the battery. In my case, the charge block is mounted using a hinged mounting.

Battery discharge unit


The discharge unit is more complex and requires precision in the selection of components. It is based on a comparator type lm393, lm339 or lp239, the function of which is to supply a “logical one” or “zero” signal to the gate of a field-effect transistor. When the field-effect transistor opens, it connects a load in the form of a resistor to the battery, the value of which determines the discharge current. When the battery voltage drops to the set shutdown threshold of 1 (Volts). The comparator slams shut and sets a logical zero at its output. The transistor comes out of saturation and disconnects the load from the battery. The comparator has hysteresis, which causes the load to be reconnected not at a voltage of 1.01 (V) but at 1.1-1.15 (V). You can simulate the action of the comparator by downloading. By selecting the resistor values, you can adjust the device to the voltage you need. For example: by raising the shutdown threshold to 3 Volts, you can make a discharge for li-on and Li-Po batteries.
You can it was designed to use the lm393 comparator in a DIP package. The comparators must be powered from a stabilized 5-volt source; its role is played by a TL-431 amplified by a transistor.