Due to the rapid development of portable devices of modern household appliances, Ni-Cd and Ni-NiMh rechargeable batteries are now widely used, the service life of which is highly dependent on proper operation. In this regard, there is a need for a device that has the ability to measure the basic technical characteristics of batteries in use, such as capacity and internal resistance, as well as provide the batteries with an optimal charging mode.
The author of the article purchased a Canon A710IS camera, which uses two AA batteries as a power source. Almost immediately it became clear that the camera could function normally only with expensive alkaline batteries costing from 5 UAH ($0.7). With cheaper batteries, it either refused to turn on, or took only a few pictures, and then turned off. In this regard, almost immediately, two GP batteries with a capacity of 2700 mAh were purchased. With these GP batteries, the camera could function normally for about a month, and approximately 2GB of photos and videos could be taken.
After a year of operation, the number of pictures that the camera could take after the batteries were fully charged began to decrease catastrophically. In addition, it was noticed that the self-discharge of batteries has increased.
After a year and a half of operation, the camera became almost impossible to use - after the batteries were fully charged, it was possible to take no more than 20-30 pictures (or 6-7 minutes of video), and if the camera was not used for more than a week, it, as a rule, even didn't turn on. And this despite the fact that there were no more than 30 actual charge cycles, with the manufacturer’s indicated resource being up to 1000...
Since the batteries were charged with a Chinese-made charger and no charge-discharge cycles were performed to prevent sulfation, it was concluded that the possible cause of premature battery failure was improper charging mode and lack of discharge-charge training cycles.
When trying to restore batteries using the method of discharge-charge cycles, it turned out that the capacity of the batteries was a little more than 1000 mAh and they could not be restored (the capacity was checked by discharging fully charged batteries onto an incandescent light bulb, and the light time of the light bulb and the current consumption were approximately determined capacity). At the same time, checking the capacity of 5-year-old Energizer 2300mAh batteries showed a capacity of about 1400mAh, however, in the camera they showed results approximately similar to GP batteries, with only one positive difference - the self-discharge was less - the camera turned on even after two weeks, but could take no more than 10 photos.
After all the experiments, it was decided to purchase new batteries and assemble a charger that would meet the following requirements:
- it was very simple in circuit design and did not contain expensive components;
- had the ability to accelerate battery charging and conduct training discharge-charge cycles;
- during charging and discharging, the consumed/distributed capacity in mAh was calculated. with direct measurement of current and at the end of the charge the internal resistance of the battery was determined;
- the end of charging was determined using the ∆U method and there was control of the battery temperature;
- it was possible to control the charging process on a computer to visualize it, as well as evaluate the decision to complete the charge;
For quite a long time, a search was carried out on the Internet and various magazines for a suitable scheme, but they were either too uninformative, too complex, or did not provide the required technical characteristics.
In the end, the charger (hereinafter referred to as charger) was based on a circuit with , adapted for charging two Ni-Cd or Ni-Mg batteries of the same type. In addition, a three-digit LED indicator was added and new software was written. The charger diagram is shown in Fig. 1.
Rice. 1
A special feature of the circuit is the constant measurement of current during the charge-discharge process, which reduced the requirement for its stability and made it possible to make a more accurate calculation of the capacity.
The device requires two power supplies to power it. The first of them, connected to X2-X4, should have a characteristic close to the current source, with an open circuit voltage of about 4..6V, and a current corresponding to the desired charging current.
The second one, connected to X3-X4, must be a voltage source, with a voltage of 6...11V and a current of at least 50mA to directly power the control and indication circuit. If the voltage of this source is at least 8V, then instead of the expensive low-dropout stabilizer LM2940-5 (DA2), you can use the common stabilizer L7805 (KREN5A).
In practice, a charger was taken from an unknown phone, on which DC 5.0V/740mA was written. In fact, at idle it produced 7V, and the charging current, when connected to two batteries connected in series, was 580mA. This charger (shown as ZU in the diagram) was modified as follows. The 4.7uF 400V capacitor was replaced by 10uF 400V, for safety a 0.25A fuse was added instead of the resistor used for this purpose, a small radiator was attached to the high-voltage transistor 13003 in the TO-126 case (like the domestic KT815), and, most importantly, on the transformer an additional winding of 15 turns of wire with a diameter of 0.18 mm (in diagram W2) was wound in series with the existing one, after which a VD10 diode of type 1N5819 and a capacitor C2 220 uF 25V were soldered onto the surface. It is necessary that when winding an additional winding W2, the winding direction is the same as in the existing W1 - the voltage on the windings must be summed up. The VD10 diode and capacitor C2 were glued with hot glue directly to the transformer.
The whole rework took about an hour and a half. As a result, even at the beginning of charging completely discharged new batteries, the voltage at contact X3 did not drop below 7V, while the charge current was 640mA. At the end of the charge, the current dropped to 560mA. This made it possible to charge completely discharged 2700 mAh batteries in 5 hours. If it is necessary to increase the charge current, you should use a more powerful flyback switching power supply, converted in a similar way, or use a separate power supply as a current source (X2-X4) (more preferable).
The control circuit is based on a common microcontroller from Atmel - Atmega 8A. The controller is set to an internal oscillator with a frequency of 1 MHz. The PC0 and PC1 pins of the controller are configured as ADC inputs. Resistors R8, R6 and R7, R5 form dividers to match the voltage on the batteries with the internal reference voltage source of the ADC controller - 2.56V. Thanks to the dividers, the maximum measured voltage was 2.56/3*(3+1.5)=3.84V. Zener diodes VD5, VD6 serve to limit the voltage at the inputs to 4.5 V, capacitors C11, C12 - to filter the measured voltage.
By measuring the voltage before and after resistor R13, it became possible to measure the charge current, and the requirement for stability of the charge current was reduced. When calculating the capacity, the device measures the charging current in mA every second and sums it up. The display shows the amount divided by 3600, i.e. consumed (distributed) capacity in mAh. Resistor R13 consists of three 1 Ohm 0.25 W resistors connected in parallel.
The HL2 device uses a three-digit common cathode LED indicator KOOHI E30361LC8W. When tested, it turned out that even with a current of 2 mA per segment, the brightness of the glow was quite intense. This made it possible to do without additional transistors by connecting the cathodes directly to the controller ports, since the total current did not exceed the 40 mA per port allowed by the datasheet. As it turned out later, the indicator also works normally without diodes VD7,8,9. Any similar indicator can be used. If the glow intensity is insufficient, it is possible to reduce the quenching resistors to 560 Ohms.
L1, C3, C4 serve for additional filtering of the controller power supply. Connector X1 is designed to connect the charger to the computer. Parts R1, R2, R25, R26, VD1, VD2 are used to protect the controller from improper connection to an external device (computer). If such a connection is not planned, their use is not necessary.
Button SA1 is used to select the operating mode of the charger when it is turned on. LED VD4 serves for additional indication of the current operating mode of the charger. Its presence allows you to use the charger without the HL2 indicator (if there is no need for additional information about the charging process). The PB6 port is used programmatically both as an input to poll the button (when the LED is off), and as an output to indicate the operating mode.
The DS18B20 sensor is used to measure battery temperature. It must be located as close to the batteries as possible. In the author's version, the sensor was fixed between the batteries directly in the holder, with the hemisphere facing the batteries. If it is absent, the device also works, but accordingly, the temperature is not displayed.
Elements VT1,VT2,VT3,R11,R12,R9,R10 form the charging current switch. Any low-power n-p-n transistor (for example, KT315B) can be used as transistor VT1, but it is necessary to increase resistor R9 to 4.7 kOhm. VT2 can be any similar one with a current transfer coefficient of at least 50.
VT4,R14,R15,R16 form a bit key. When transistor VT4 is turned on, the battery discharge current flows through resistors R13, R16 and is limited by them at a level of about 410 mA. Since the discharge current flows through resistor R13, it is possible to measure the discharge current and calculate the capacity given by the battery, eliminating the need for discharge current sources. As a transistor VT4, it is possible to use a composite n-p-n transistor, for example KT972, KT827, in this case it is necessary to increase the resistance R14 to 1.5 kOhm.
Connector XS1 is intended for in-circuit programming of the controller.
With partial use of SMD elements, the board size was 69x50mm. The LED indicator was fixed directly to the charger housing with hot-melt adhesive and connected to the board using MGTF wires. The case for the entire device was taken from the power supply of the SEGA console, measuring 80x55x50mm. A groove was cut into the case for the battery holder, which was glued in with hot-melt adhesive on the inside. The appearance of the board is shown in photo 1, the layout of the components inside the case in photo 2, the appearance of the entire memory in photo 3.
Photo 1
Photo 2
Photo 3
To connect the circuit to a computer, you need an adapter (data cable) assembled on a MAX232 or its equivalent. The author's diagram was assembled according to Fig. 2. The Tx pin of the adapter must be connected to the Rx pin of the device, and the Rx of the adapter, respectively, to the Tx pin of the device.
Rice. 2
When developing a program for the device, the algorithm described in .
The charger operating algorithm consists of several phases:
1. Determining the presence of a battery.
2. Selecting the operating mode.
3. Rank (if selected)
4. Pre-charge.
5. Fast charging.
6. Top-off charge.
7. Maintenance charge.
In the phase of determining the presence of a battery, the charging current switch VT2 is turned on, and the voltage at the holder terminals is measured. If the voltage is higher than 3.3V, then there are no batteries. At the same time, dashes “---” are displayed on the indicator. A decrease in voltage below 3.3V is regarded as the appearance of batteries, while the HL2 indicator goes out and the VD4 LED begins to blink at a frequency of five times per second.
If within 25 sec. the SA1 button will not be pressed, the device “remembers” its last mode stored in the EEPROM and begins to work out it. Those. if there was a power failure, the device will continue to charge the batteries if the last mode was charging, or will switch to trickle charging mode if charging was completed. The only “but” is that information about the charge (discharge) capacity will be lost, the charger will start counting again. This prevents fully charged batteries from being recharged during a power outage.
If the SA1 button during the first 25 seconds. will still be pressed, the HL2 indicator first displays the battery voltage (the total voltage is divided by two, i.e. the average voltage per battery is displayed), then “ЗР1” will start flashing - charging mode without a discharge pulse. If you press the button again, the “ЗР2” mode will be highlighted - charge mode with a discharge pulse. The next time you press, “ONE” will be displayed - discharge mode followed by charging in “ZR2” mode. Then - in a circle, while the VD4 LED flashes in accordance with the selected mode (see below). You have 10 seconds to select a mode. since the last button press.
If discharge mode has been selected, the batteries are first discharged to a voltage of less than 0.8V per battery. In this case, the following information is displayed on the indicator in the cycle: “TIME” (mode), “U”, “voltage per battery” (in volts), “A”, “discharge current” (in amperes), “AcH”, “ discharge capacity" (in ampere-hours). The VD4 LED flashes twice per second. If the discharge lasts more than nine hours, “ErH” is displayed - a time error. After discharge, the charger always switches to the “ZR2” fast charge mode.
The fast charge mode (both ZR1 and ZR2) is always preceded by a precharging phase. In this case, the charging current is supplied for 300ms, followed by a pause of 700ms. Those. the average current is 30% of that measured at the moment the current is applied. In this case, the following information is displayed on the indicator: “NZR” (initial charge mode), “U”, “voltage per battery”, “A”, “current in amperes” (average current), “t”, “temperature” ( in degrees Celsius). The last two values are not displayed if the sensor is not connected or the measured temperature is less than 1°C. The VD4 LED blinks once every two seconds with short flashes. The precharging phase lasts at least 1 minute. The main condition for the transition to the main charging mode is to increase the voltage on the batteries to more than 1V per battery. If within 30 min. It is not possible to “boost” the batteries, the error “ErU” is displayed - voltage error.
Fast charging modes ZR1 and ZR2 occur as follows. The charging current turns on. Once a second the charging current is turned off and there is a short pause of 5ms. for stabilization. Then for 16ms. Six battery voltage measurements are taken in a row, after which the voltage is averaged. If the 3Р1 mode is selected, then after the measurements the charging current is turned on again. If the ZP2 mode is selected, then after the measurements the transistor VT4 is turned on, and a discharge current flows through the batteries for 5 ms, after which VT4 is turned off, and VT1, VT2, VT3 are turned on again - the charging current begins to flow again.
The advantage of the ZR1 method is the better equalization of the concentration of active substances throughout the entire volume, the lower probability of the formation of large crystalline formations on the electrodes and their passivation. An additional advantage of this method is that the voltage is measured without the flow of charging current, and the influence of contact resistance and internal battery resistance on the measurement accuracy is practically eliminated. The mode with a discharge pulse (ЗР2) is called FLEX negative pulse charging or Reflex Charging. The advantage of this method is the lower temperature of the battery during charging and the ability to eliminate large crystalline formations on the electrodes (causing the “memory” effect).
During the charging process, the following information is displayed in a cycle on the HL2 indicator: “ЗР1” (or “ЗР2”, if the mode is ЗР2), “U”, “voltage per battery”, “A”, “current in amperes”, “AcH” , “charge capacity”, “t”, “temperature”, “dt”, “temperature increment”. The last four values are not displayed if the DS18B20 temperature sensor is not present. In ZR1 mode, the VD4 LED blinks once per second with equal intervals of pause and illumination. In ZR2 mode – also once per second, but with a long pause and short illumination.
After 15 min. After the fast charging process begins, the charger remembers the initial temperature of the batteries. Subsequently, the device displays the dt parameter - the increase in temperature since the beginning of the charge. The initial temperature is remembered after 15 minutes. in order to reduce the effect of heating from the power supply, after turning it on, to the full charge current. Increasing the dt parameter to 15°C is one of the conditions for ending the charge. The fact is that at the end of the charge, the energy transmitted by the charger ceases to be absorbed by the batteries and is almost completely converted into heat. This causes a violation of the thermal balance, and the temperature begins to rise to a certain new value, at which the energy received by the batteries from the charger will not be equal to the energy released by the batteries into the environment. The energy released by batteries into the environment, to a first approximation, depends on the geometry of the batteries (which has not changed since the beginning of charging), and the temperature difference between the batteries and the environment. Thus, for each charge current, there will be a fairly constant value of the temperature increment at the end of the charge. It is an increment, and not any specific temperature value. It was experimentally determined that for a charge current of 600 mA and AA battery format, the temperature increment at the end of the charge is 11...13 ° C. Since this method was used by the author as an additional one, the increment value was chosen with a margin of 15°C. In practice, the end of the charge by dt occurs quite rarely, as a rule, with old high-capacity batteries.
The main criterion for determining the end of charging is a decrease or constant voltage over a 10-minute interval, i.e. dV£0. The storage memory contains an array of ten cells. The memory measures the voltage every second and adds it to the previous values. Once every 60 sec. averaging is carried out, i.e. the resulting sum is divided by 60, then the array is shifted, and the resulting value is written to the free cell, and the sum counter is reset to zero. Thus, the voltage values for the last ten minutes are always available, at one-minute intervals. After this, a check is carried out for dV £ 0, i.e. all previous voltage values must be greater than or equal to the last U i ³U 10. However, after testing the device, the condition had to be slightly supplemented. The fact is that the ADC is discrete, and in this device it has 1024 steps, relative to the reference voltage, 2.56V. Taking into account the resistive dividers, the step step is about 3.7 mV. Thus, even if the voltage on the battery does not increase, but is in the middle of the step, the ADC produces a “floating” voltage by the value of the step. Due to multiple averaging (360 measurements are averaged per minute), the actual voltage fluctuation in the array at a constant battery voltage was 2 mV. This delayed the moment of determining the end of charging, which often led to the end of charging when the temperature dt was exceeded. In this regard, the condition was somewhat relaxed - out of nine checks of conditions, 5 had to strictly comply with the condition U i ³U 10, and four could deviate from it by no more than 2 mV, i.e. if U i 10, then (U 10 - U i) £2mV. After this change, repeated analysis of the charging curves showed the stability of the charger operation.
During fast charging of ZR1 and ZR2, the following accidents are possible: when the charging time is more than 9 hours. – time error “ErH”, when delivering more than 3800 mAh to the battery – capacity error – ErA, if after detecting the end of the charge, the voltage on two batteries is less than 2.5V – voltage error “ErU”. In error mode, the VD4 LED flashes five times per second.
After detecting the end of charging (dV or dt), or if the batteries heat up to a critical temperature of 50°C during charging, the charger goes into recharging mode. This mode lasts 20 minutes. and serves to equalize the battery charge in the battery. If the battery temperature is more than 40°C, the recharging current is 5%, if less than 40°C - 20% of the charging source current. The amount of recharging current is regulated by the pulse method, as well as in the precharging mode.
During the recharging process, the HL2 indicator displays information in a cycle similar to the main charge mode, only the mode is indicated as “dЗР”, and the temperature rise information “dt” is not displayed. The VD4 LED blinks at a frequency of once every two seconds with long flashes.
After the end of the additional charging mode, the charger switches to the maintenance drip charge mode with 0.5% current. In this case, once, immediately after the end of recharging, an approximate calculation of the internal resistance of the batteries is made, based on measuring the voltage of the batteries without load, as well as under load with discharge resistance, according to the formula R in = (E emf * 5.97)/U load - 5.97, where 5.97 is the load resistance (0.33+5.1+0.54 (transistor resistance)). The following information is displayed on the indicator: “OK”; “dU” - if there was a trigger according to the dV£0 method, or “dt” - if there was a trigger according to the condition of exceeding the temperature dt; "U"; “voltage per battery at the end of charge”; "E-Z"; "charge capacity"; “E-P” (if there was a discharge mode); “discharge capacity” (if there was a discharge mode); "rVN"; “internal resistance at the end of the charge” (in Ohms). The VD4 LED is constantly lit. The charging process is completed.
To visualize the process, an application was created in the free graphical programming environment Hi-Asm (http://hiasm.com). There are a sufficient number of examples on the website of the author of the Hi-Asm environment and on the Internet; the author of this article needed only four evenings to create a memory application without any programming skills in languages of a similar level. To start the entire complex, you must first connect the adapter cable to the charger and the COM1 port of the computer, run the CHARGER.exe application, then install the batteries in the charger and apply power. After the voltage is indicated on the display, select the required charging mode: ZR1, ZR2 or ONCE using the SA1 button. After starting the corresponding mode, you must press the “CYCLE” button in the CHARGER application, as a result, graphs of changes in the temperature and voltage of the batteries will begin to be built during the charging process. After pressing the “CYCLE” button, the application sends a request to the memory in the form of code 0x0F once a minute. In response, the memory sends a packet of eight bytes: four bytes of battery voltage in mV (without a comma), then three bytes of temperature (the first two are integers, then the tenths without a comma), and at the end the CR code (13). All data is sent in ACS|| code. When the charging process is completed, the charger transmits zeros in all data, as a result a window appears with the inscription “Charging complete.”
For example, the charge graphs for GP 2700 mAh batteries (age 1.5 years) are shown - Fig. 3, DURACEL 2650mAh (new) - Fig. 4., of unknown origin with the inscription 700 mAh from a radio-controlled car (six months old) - Fig. 5.
Figure 3 shows graphs of battery charge from the camera described at the beginning of the article. As you can see, the batteries were able to deliver only 1210 mAh immediately after charging, the efficiency of the charging process was only about 67%, the batteries had a fairly high internal resistance - 0.52 Ohm (for two batteries connected in series). There was no voltage drop at the end of the fast charge. Since the efficiency of the process was low, the temperature increased quite rapidly throughout the entire time, although the increase in temperature at the end of the charge is still quite obvious.
Rice. 3. GP 2700mAh (age 1.5 years) R in =0.52 Ohm, E charge =1.79A/h, E times =1.21A/h
In Fig. Figure 4 shows charge graphs for DURACEL batteries purchased to replace GP. Here the graphs are like from a textbook - a clear voltage peak with a drop of 5 mV. The temperature practically does not increase during the charging process, and has a very pronounced sharp increase at the end of the charge, with a growth rate of 0.3 ° C/min. The efficiency of the process is about 90%, and the battery resistance is 0.21 Ohm. The camera on one charge of these batteries was able to capture 7GB of photos and videos over two months of intensive use!
Rice. 4 DURACEL 2650mAh (new) R in = 0.21 Ohm, E charge = 2.95 A/h, E times = 2.66 A/h
Well, the last graphs in Fig. 5 shows the charging process of batteries from an unknown Chinese manufacturer. The radio-controlled car, which was equipped with these batteries, practically stopped functioning after six months - the battery charge lasted for 1-2 minutes. As you can see, their actual capacity is only 110mAh, instead of the promised 700mAh. The voltage graph shows that they can hardly be called batteries...
Rice. 5 Unknown 700 mAh (age vn = 0.27 Ohm, E charge = 0.23 A/h, Eraz = 0.11 A/h
The charger requires virtually no adjustment. It may be necessary to adjust the voltage dividers, since a rather large error is possible due to the spread of ratings. To do this, you need to install pre-charged batteries in the charger and turn it on in discharge mode. In this mode, by selecting R6 or R8, calibrate the indicated battery voltage displayed on the HL2 indicator using a reference voltmeter connected directly to the batteries. After this, connect a reference ammeter in series with the batteries, and select R5 or R7 (also in discharge mode) to calibrate the indicated current. The second way is to calibrate with a correction factor inside the program; how and where to change is in the notes of the source code.
The firmware of the microcontroller was carried out using a regular LPT programmer consisting of 4 resistors (it can be found on the Internet without much difficulty). Programmed fuses: CKSEL3=CKSEL2=CKSEL1=SUT0=0 – checkboxes. Instead of Atmega 8A, you can use Atmega 8.
When planning the layout of memory elements inside the case, it is necessary to minimize the influence of heating of the batteries from the components of the power supply and board!
When using the charger together with DURACEL batteries, an interesting fact emerged: if the batteries are practically not used for more than a month and a half, their capacity after discharge-charge is only 1700...1800 mAh, however, after one or two discharge-charge cycles, the capacity is restored to 2600 mAh. But nothing helped the old GP and Energizer batteries - over time, their capacity steadily decreased. The conclusion suggests itself - if you don’t use batteries, then do training cycles with them at least once a month.
Hex-codes of the controller firmware, the original project in C (for ), circuit diagram and board layout (), the CHARGER.exe application, its source in Hi-Asm (v.4.03) are attached to the article.
Literature
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad | |
|---|---|---|---|---|---|---|---|
| Picture 1. | |||||||
| DA1 | MK AVR 8-bit | ATmega8 | 1 | To notepad | |||
| DA2 | Linear regulator | LM2940-N | 1 | To notepad | |||
| temperature sensor | DS18B20 | 1 | To notepad | ||||
| VT1, VT4 | MOSFET transistor | IRLL110 | 2 | To notepad | |||
| VT2 | bipolar transistor | KT814A | 1 | To notepad | |||
| VT3 | bipolar transistor | KT3107A | 1 | To notepad | |||
| VD1, VD2, VD5, VD6 | Zener diode | 4.5 V | 4 | To notepad | |||
| VD3, VD10 | Schottky diode | 1N5819 | 2 | To notepad | |||
| VD4 | Light-emitting diode | Any red | 1 | To notepad | |||
| VD7-VD9 | Diode | KD522A | 3 | To notepad | |||
| C1, C6 | 1000 µF 16 V | 2 | To notepad | ||||
| C2, C7 | Electrolytic capacitor | 220 µF 25 V | 2 | C7 can be used at 16 V | To notepad | ||
| C3 | Electrolytic capacitor | 100 µF | 1 | To notepad | |||
| C4, C5, C8-C12 | Capacitor | 0.1 µF | 7 | To notepad | |||
| R1, R2, R9, R14, R25, R26 | Resistor | 100 Ohm | 6 | To notepad | |||
| R3, R10, R15 | Resistor | 10 kOhm | 3 | To notepad | |||
| R4 | Resistor | 560 Ohm | 1 | To notepad | |||
| R5, R6 | Resistor | 3 kOhm | 2 | To notepad | |||
| R7, R8 | Resistor | ||||||
Nickel-metal hydride batteries are gradually spreading on the market, and their production technology is being improved. Many manufacturers are gradually improving their characteristics. In particular, the number of charge-discharge cycles increases and the self-discharge of Ni─MH batteries decreases. This type of battery was produced to replace Ni─Cd batteries and is gradually pushing them out of the market. But there remain some areas of use where nickel-metal hydride batteries cannot replace cadmium ones. Especially where high discharge currents are required. Both types of batteries require proper charging to extend their service life. We have already talked about charging nickel-cadmium batteries, and now it’s the turn to charge Ni-MH batteries.
During the charging process, a series of chemical reactions take place in the battery, which uses part of the supplied energy. The other part of the energy is converted into heat. The efficiency of the charging process is that part of the supplied energy that remains in the “reserve” of the battery. The efficiency value may vary depending on charging conditions, but is never 100 percent. It is worth noting that the efficiency when charging Ni-Cd batteries is higher than in the case of nickel-metal hydride batteries. The process of charging Ni─MH batteries occurs with a large release of heat, which imposes its own limitations and features. Read more about this in the article at the given link.
By and large, there are only two types of charging: drip and accelerated. Fast and accelerated are practically the same thing. They differ only in the method of stopping the charging process.
In general, any charging of Ni─MH batteries with a current greater than 0.1C is fast and requires monitoring of some criteria for the end of the process. Trickle charging does not require this and can continue indefinitely.
Now, let's take a closer look at the features of different types of charging.
It is worth saying here that this type of charging does not increase the service life of Ni─MH batteries. Since trickle charging does not turn off even after a full charge, the current is selected very small. This is done to ensure that the batteries do not overheat during long-term charging. In the case of Ni─MH batteries, the current value can even be reduced to 0.05C. For nickel-cadmium, 0.1C is suitable.
With drip charging, there is no characteristic maximum voltage and the only limitation for this type of charging can be time. To estimate the required time, you will need to know the capacity and initial charge of the battery. To calculate charging time more accurately, you need to discharge the battery. This will eliminate the influence of the initial charge. The efficiency of trickle charging of Ni─MH batteries is 70 percent, which is lower than other types. Many manufacturers of nickel-metal hydride batteries do not recommend using trickle charging. Although recently more and more information has appeared that modern models of Ni─MH batteries do not degrade during the trickle charging process.
Manufacturers of Ni─MH batteries in their recommendations provide characteristics for charging with a current value in the range of 0.75─1C. Focus on these values when choosing what current to charge Ni─MH batteries. Charge currents higher than these values are not recommended as this may cause the safety valve to open to relieve pressure. It is recommended to quickly charge nickel-metal hydride batteries at a temperature of 0-40 degrees Celsius and a voltage of 0.8-8 volts.
The efficiency of the fast charging process is much greater than that of drip charging. It is about 90 percent. However, by the time the process is completed, the efficiency decreases sharply, and the energy turns into heat release. The temperature and pressure inside the battery rise sharply. have an emergency valve that can open when the pressure increases. In this case, the properties of the battery will be irretrievably lost. And the high temperature itself has a detrimental effect on the structure of the battery electrodes. Therefore, we need clear criteria by which the charging process will be stopped.
We will present the requirements for the charger (charger) for Ni─MH batteries below. For now, we note that such chargers charge according to a certain algorithm. The stages of this algorithm are generally as follows:
At this stage, a current of 0.1C is applied and the voltage at the poles is checked. To start the charging process, the voltage should be no more than 1.8 volts. Otherwise the process will not start.
It is worth noting that checking for the presence of a battery is carried out at other stages. This is necessary in case the battery is removed from the charger.
If the memory logic determines that the voltage value is greater than 1.8 volts, then this is perceived as the absence of a battery or its damage.
Here you can determine an approximate estimate of the battery charge. If the voltage is less than 0.8 volts, then fast charging of the battery cannot be started. In this case, the charger will turn on pre-charging mode. During normal use, Ni─MH batteries rarely discharge to voltages below 1 volt. Therefore, pre-charging is activated only in the case of deep discharges and after long-term battery storage.
As mentioned above, pre-charging is activated when Ni─MH batteries are deeply discharged. The current at this stage is set at 0.1─0.3C. This stage is limited in time and lasts somewhere around 30 minutes. If during this time the battery does not restore the voltage to 0.8 volts, then the charge is interrupted. In this case, the battery is most likely damaged.
At this stage, there is a gradual increase in the charging current. The current increases smoothly over 2-5 minutes. At the same time, as at other stages, the temperature is controlled and the charge is turned off at critical values.
The charge current at this stage is in the range of 0.5─1C. The most important thing at the fast charging stage is to turn off the current in a timely manner. To do this, when charging Ni─MH batteries, control is used according to several different criteria.
For those who are not aware, the delta voltage control method is used when charging. During the charging process it constantly grows, and at the end of the process it begins to fall. Typically, the end of the charge is determined by a voltage drop of 30 mV. But this control method does not work very well with nickel-metal hydride batteries. In this case, the voltage drop is not as pronounced as in the case of Ni─Cd. Therefore, to trigger the shutdown, you need to increase the sensitivity. And with increased sensitivity, the likelihood of false alarms due to battery noise increases. In addition, when charging several batteries, the operation occurs at different times and the whole process is blurred.
But still, stopping charging due to a voltage drop is the main thing. When charging with a current of 1C, the voltage drop to turn off is 2.5-12 mV. Sometimes manufacturers set detection not by a drop, but by the absence of a change in voltage at the end of the charge.
In this case, during the first 5-10 minutes of charging, the voltage delta control is turned off. This is because when fast charging starts, the battery voltage can change greatly as a result of the fluctuation process. Therefore, at the initial stage, the control is turned off to eliminate false alarms.
Due to the not very high reliability of switching off charging based on the voltage delta, control is also used based on other criteria.
There is also a method for monitoring the charging process by analyzing the voltage derivative. In this case, it is not the voltage delta that is monitored, but the rate of its maximum increase. The method allows you to stop fast charging slightly before the charge is complete. But such control is associated with a number of difficulties, in particular, more accurate voltage measurement.
Some chargers for Ni─MH batteries use pulsed rather than direct current for charging. It is delivered for a duration of 1 second at intervals of 20-30 milliseconds. Experts cite a more uniform distribution of active substances throughout the battery volume and a reduction in the formation of large crystals as the advantages of such a charge. In addition, more accurate voltage measurements are reported between current injections. As a development of this method, Reflex Charging was proposed. In this case, when applying a pulsed current, the charge (1 second) and discharge (5 seconds) alternate. The discharge current is 1─2.5 times lower than the charge. The advantages include a lower temperature during charging and the elimination of large crystalline formations.
When charging nickel-metal hydride batteries, it is very important to monitor the end of the charging process using various parameters. Emergency termination methods must be provided. For this purpose, the absolute temperature value can be used. Often this value is 45-50 degrees Celsius. In this case, the charge must be interrupted and resumed after cooling. The ability of Ni─MH batteries to accept a charge at this temperature decreases.
It is important to set a charge time limit. It can be estimated by the capacity of the battery, the magnitude of the charging current and the efficiency of the process. The limit is set at the estimated time plus 5-10 percent. In this case, if none of the previous control methods work, the charge will turn off at the set time.
At this stage, the charging current is set to 0.1─0.3C. Duration about 30 minutes. Longer recharging is not recommended as it will shorten battery life. The recharging stage helps to equalize the charge of the cells in the battery. It is best if, after fast charging, the batteries cool down to room temperature, and then recharging starts. Then the battery will restore its full capacity.
Chargers for Ni─Cd batteries often switch the batteries into trickle charging mode after completing the charging process. For Ni─MH batteries, this will only be useful if a very small current is supplied (about 0.005C). This will be enough to compensate for battery self-discharge.
Ideally, the charger should have the function of enabling maintenance charging when the battery voltage drops. Maintenance charging only makes sense if a sufficiently long time elapses between charging the batteries and using them.
And it’s also worth mentioning the ultra-fast charging of batteries. It is known that when charged to 70 percent of its capacity, a nickel-metal hydride battery has a charging efficiency close to 100 percent. Therefore, at this stage it makes sense to increase the current to speed up its passage. In such cases, currents are limited to 10C. The main problem here is determining those 70 percent of the charge at which the current should be reduced to normal fast charging. This greatly depends on the degree of discharge at which the battery began charging. High current can easily lead to overheating of the battery and destruction of the structure of its electrodes. Therefore, the use of ultra-fast charging is recommended only if you have the appropriate skills and experience.
It is not practical to disassemble any individual models for charging Ni─MH batteries within the framework of this article. It is enough to note that these can be narrowly targeted chargers for charging nickel-metal hydride batteries. They have a hard-wired charging algorithm (or several) and constantly work according to it. And there are universal devices that allow you to fine-tune charging parameters. Eg, . Such devices can be used to charge various batteries. Including for, if there is a power adapter of appropriate power.
It is necessary to say a few words about what characteristics and functionality a charger for Ni─MH batteries should have. The device must be able to adjust the charging current or set it automatically depending on the type of batteries. Why is it important?
Now there are many models of nickel-metal hydride batteries, and many batteries of the same form factor may differ in capacity. Accordingly, the charging current should be different. If you charge with a current higher than normal, there will be heating. If it is below normal, the charging process will take longer than expected. In most cases, the currents on chargers are made in the form of “presets” for standard batteries. In general, when charging, manufacturers of Ni-MH batteries do not recommend setting a current of more than 1.3-1.5 amperes for type AA, regardless of capacity. If for some reason you need to increase this value, then you need to take care of forced cooling of the batteries.
Another problem involves the charger cutting off power during charging. In this case, when the power is turned on, it will start again from the battery detection stage. The moment at which fast charging ends is determined not by time, but by a number of other criteria. Therefore, if it has passed, it will be skipped when turned on. But the recharging stage will take place again, if it has already happened. As a result, the battery receives unwanted overcharging and excess heating. Among other requirements for the charger of Ni-MH batteries is a low discharge when the charger is turned off. The discharge current in a de-energized charger should not exceed 1 mA.
It is worth noting that the charger has another important function. It must recognize primary current sources. Simply put, zinc-manganese and alkaline batteries.
When installing and charging such batteries in a charger, they may well explode, since they do not have an emergency valve to relieve pressure. The charger is required to be able to recognize such primary current sources and not initiate charging.
Although it is worth noting here that determining batteries and primary current sources has a number of difficulties. Therefore, memory manufacturers do not always equip their models with similar functions.
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
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?
There is often no need to design complex devices that take into account many parameters of the discharge-charge cycle of batteries. It is enough to take into account a couple of parameters such as end-of-discharge voltage, end-of-charging voltage and charging current. Selected cycle parameters prevent overcharging or undercharging of batteries, which subsequently increases their service life.
The device is powered from an unstabilized source with an output current of at least 100 mA, the voltage of which, taking into account ripple, should be within 11.5...30 V.
Scheme:
Device operation:
First, a battery of four batteries is connected to the charger and then the supply voltage is applied. While the battery voltage exceeds 4 V (on average 1 V per cell), transistor VT1 is open, transistors VT2-VT4, diodes VD1-VD4 and thyristor VS1 are closed. Transistor VT5 is open and saturated, through it and resistor R13 the battery is discharged. HL2 LED is on. The discharge current should not be set to more than 1/10 of the battery capacity.
When the battery voltage drops below 4 V during discharge, the Schmitt trigger will switch, transistor VT1 will close, and VT2 will open. The output of the Schmitt trigger will be set to a high voltage (about 8 V). Diode VD1 and thyristor VS1 open, as a result of which diode VD3 opens, transistor VT5 closes, LED HL2 goes out, and the discharge mode stops. At the same time, the high-level voltage from the output of the Schmitt trigger will open diode VD2 and transistor VT3, as a result of which LED HL1 will light up, transistor VT4 and diode VD4 will open, through which the battery will begin charging with a stable current.
By pressing the SB1 button, the device forcibly switches from discharging mode to charging mode. This is necessary if Ni-MH batteries are used, which are not subject to the “memory effect” and, accordingly, do not need to be pre-discharged.
During charging, when the battery voltage reaches 5.92 V (average 1.48 V per cell), the Schmitt trigger will switch: transistor VT1 will open and VT2 will close. Diode VD2 and transistor VT3 will close, LED HL1 will go out, as a result of which transistor VT4 and diode VD4 will close, and the charging process will stop. But the thyristor VS1 remains open, so the transistor VT5 will not open and the discharge mode will not turn on. After turning off the power of the device, you must disconnect the battery from it, otherwise it will be discharged.
Installation and components:
Transistors KT315B (VT1-VT3) can be replaced with transistors KT315G or KT315E. You can use other low-power silicon transistors of the n-p-n structure with a maximum collector current of at least 100 mA, but for a Schmitt trigger it is advisable to select transistors with a base current transfer coefficient of at least 50. Transistors VT4 and VT5 - any of the KT814, KT816 series. They are mounted on heat sinks made of strips of soft aluminum measuring 28x8 mm and 1 mm thick, bent in the shape of the letter "U". Diodes - any low-power silicon, except VD4, which must withstand the charging current. Trimmer resistors R2 and R5 are multi-turn SP5-2. It is advisable to use LEDs HL1 and HL2 in different colors to clearly indicate the operating mode of the device.
Setting:
To set up the device, you need an auxiliary battery of 9... 12 V, to which a variable resistor with a resistance of several kOhms is connected by a potentiometer. To make it easier to accurately set the required voltage in the open circuit of one of the extreme terminals of this resistor, it is advisable to include another variable resistor with ten times less resistance as a rheostat.
The engines of trimming resistors R2 and R5 are set to the lowest position according to the diagram. Temporarily break the connection of the left resistor R1 according to the output circuit with the positive output of the device. During setup, this output becomes the input of the device, which is connected to the variable resistor motor. The negative terminal of the auxiliary battery is connected to the common wire of the device. The battery being charged is not connected to the output. After turning on the power, you need to make sure that there is a stable voltage of 9 V at the output of the DA1 chip.
Then the switching thresholds are set. A voltmeter is connected to the emitter of transistor VT2. First, the slider of trimming resistor R2 sets the lower switching threshold to 4 V. When the input voltage drops below this threshold by 0.05...0.1 V, transistor VT1 should close and a high voltage level should be established at the emitter of transistor VT2. Then, using the trimmer resistor R5, the upper switching threshold is set to 5.92 V. When the input voltage increases above this threshold by 0.05...0.1 V, transistor VT2 should open and a low voltage level should be established at the emitter of transistor VT2. Check both switching thresholds.
Next, check that after transistor VT2 opens, thyristor VS1 also opens. If this is not the case, reduce the resistance of resistor R6, achieving clear opening of the SCR. To turn off the thyristor, the supply voltage is briefly turned off.
Finally, a series-connected milliammeter and a rechargeable battery are connected to the output of the device. In charging mode, select resistor R9 to set the desired brightness of LED HL1, and select resistor R11 to set the required charging current. Next, disconnect the auxiliary battery and restore the connection of the left resistor R1 according to the output circuit with the positive output of the device. SCR VS1 is turned off. The multimeter is connected to the output of the device in voltage measurement mode. Observe the process of charging the battery and automatically switching the device to the discharge mode after reaching the output voltage of 5.92 V. Next, in the discharge mode, resistor R12 sets the brightness of the LED HL2 and the initial discharge current by selecting resistor R13. Then connect the thyristor VS1 and switch the device to charging mode. Upon completion, you need to make sure that the thyristor VS1 has opened and prevented the discharge mode from being activated.
Strong heating of the batteries at the end of charging indicates that the charging current is too high; it needs to be reduced, but this will increase the charging time.
G. VORONOV, Stavropol "Radio" No. 1 2012
Nimh batteries are power sources that are classified as alkaline batteries. They are similar to nickel-hydrogen batteries. But the level of their energy capacity is greater.
The internal composition of ni mh batteries is similar to the composition of nickel-cadmium power supplies. To prepare the positive terminal, a chemical element is used, nickel, while the negative terminal is prepared using an alloy that includes hydrogen-absorbing metals.
There are several typical designs of nickel metal hydride batteries:
Among the advantages of such a power source are:
Among the restrictions that relate to nickel metal hydride batteries are:
The charging process of nickel metal hydride batteries involves certain chemical reactions. For their normal operation, part of the energy supplied by the charger is required from the network.
The efficiency of the charging process is the portion of the energy received by the power source that is stored. The value of this indicator may vary. But it is impossible to achieve 100 percent efficiency.
Before charging metal hydride batteries, study the main types, which depend on the magnitude of the current.
This type of charging for batteries must be used carefully, as it leads to a reduction in service life. Since this type of charger is turned off manually, the process requires constant monitoring and regulation. In this case, the minimum current indicator is set (0.1 of the total capacity).
Since when charging ni mh batteries in this way, the maximum voltage is not set, they focus only on the time indicator. To estimate the time interval, use the capacity parameters that a discharged power source has.
The efficiency of a power supply charged in this way is about 65–70 percent. Therefore, manufacturing companies do not recommend using such chargers, since they affect the performance parameters of the battery.
When determining what current can be used to charge ni mh batteries in fast mode, the manufacturers' recommendations are taken into account. The current value is from 0.75 to 1 of the total capacity. It is not recommended to exceed the set interval, as the emergency valves are activated.
To charge nimh batteries in fast mode, the voltage is set from 0.8 to 8 volts.
The fast charging efficiency of ni mh power supplies reaches 90 percent. But this parameter decreases as soon as the charging time ends. If you do not turn off the charger in a timely manner, the pressure inside the battery will begin to increase and the temperature will increase.
To charge the ni mh battery, perform the following steps:
This mode is entered if the battery is completely discharged. At this stage, the current is between 0.1 and 0.3 of the capacitance. It is prohibited to use high currents. The time period is about half an hour. As soon as the voltage parameter reaches 0.8 volts, the process stops.
The process of increasing the current is carried out within 3–5 minutes. The temperature is monitored throughout the entire period. If this parameter reaches a critical value, the charger is turned off.
When fast charging nickel metal hydride batteries, the current is set at 1 of the total capacity. In this case, it is very important to quickly disconnect the charger so as not to harm the battery.
To monitor the voltage, use a multimeter or voltmeter. This helps eliminate false positives that adversely affect the performance of the device.
Some chargers for ni mh batteries operate not with constant, but with pulsed current. Current is supplied at specified intervals. The supply of pulsed current promotes uniform distribution of the electrolytic composition and active substances.
To replenish the full charge of the ni mh battery, at the last stage the current indicator is reduced to 0.3 of the capacity. Duration – about 25–30 minutes. It is forbidden to increase this time period, since this helps to minimize the period of operation of the battery.
Some models of chargers for nickel-cadmium batteries are equipped with a fast charging mode. To do this, the charging current is limited by setting the parameters at 9–10 of the capacity. You need to reduce the charge current as soon as the battery is charged to 70 percent.
If the battery is charged in accelerated mode for more than half an hour, the structure of the current-carrying terminals is gradually destroyed. Experts recommend using this type of charger if you have some experience.
How to properly charge power supplies, and also eliminate the possibility of overcharging? To do this, you must follow these rules:
The process of restoring ni mh batteries is to eliminate the consequences of the “memory effect”, which are associated with loss of capacity. The likelihood of this effect increasing if the unit is often incompletely charged. The device fixes the lower limit, after which the capacity decreases.
Before restoring the power source, prepare the following items:
A light bulb or a charger equipped with the appropriate mode is connected to the battery with your own hands in order to completely discharge it. After this, charging mode is activated. The number of recovery cycles depends on how long the battery has not been used. It is recommended to repeat the training process 1-2 times during the month. By the way, I restore in this way those sources that have lost 5–10 percent of their total capacity.
To calculate the lost capacity, a fairly simple method is used. So, the battery is fully charged, after which it is discharged and the capacity is measured.
This process will be greatly simplified if you use a charger, with which you can control the voltage level. It is also beneficial to use such units because the likelihood of deep discharge is reduced.
If the charge level of nickel metal hydride batteries has not been established, then the light bulb must be installed carefully. Using a multimeter, the voltage level is monitored. This is the only way to prevent the possibility of a complete discharge.
Experienced specialists carry out both the restoration of one element and the entire block. During the charging period, the existing charge is equalized.
Restoring a power source that has been in use for 2–3 years, with a full charge or discharge, does not always bring the expected result. This is because the electrolytic composition and conductive terminals are gradually changing. Before using such devices, the electrolytic composition is restored.
Watch a video about restoring such a battery.
The service life of ni mh batteries largely depends on whether the power source is allowed to overheat or be significantly overcharged. Additionally, experts advise taking into account the following rules:
If not one, but several power sources are charged at the same time, then the degree of charge is maintained at the set level. Therefore, inexperienced consumers carry out battery restoration separately.
Nimh batteries are effective power sources that are actively used to complete various devices and units. They stand out with certain advantages and features. Before using them, it is necessary to take into account the basic rules of use.
