The simplest, but most correct charger
For the first time, faced with the need to reanimate already dead batteries, I decided to study the issue and set myself the goal of “shoving in the unshoveable,” i.e. squeeze out the last of the batteries prepared for disposal. This question arose in the mid-90s - at that time the most common and used batteries were acid, alkaline, nickel-cadmium and nickel-metal hydride batteries.
I’ll say right away that the standard chargers designed for charging different batteries could no longer cope: some already at the beginning of the cycle said that nothing could be done, while others honestly went through the cycle, but the battery never gained its capacity even by 10%.
So, there are two ways to charge from a constant current source: constant (over time) current or constant (over time) voltage. However, in any case, the patient warms up and boils (if the electrolyte is liquid). Skipping all the details, I’ll move on to what I deduced for myself.
What happens is this: batteries need to be charged not only in pulses, but also discharged in pauses between charge pulses. But more importantly, DC pulses are also not very favorable. As a result, this device was born:
The simplest charger "simplest charger"
Charger circuit
This solution allows the battery to be charged and also discharged in half-cycle intervals.
R1 - the charge current is regulated, which is 10% of the battery capacity + Jdischarge.
R2 - is calculated so that during pauses in the discharge a current Jdischarge flows through it, 10 times less than the charge current. I also use incandescent lamps for this purpose if the charge currents are high.
For example, if the battery capacity is 55Ah, then the charging current must be maintained throughout the charge equal to Jcharge=5.5+0.55=6.1A.
The first experience was so promising that I couldn't believe it.
1. The 10-NKGTs-10 alkaline briquette was so dead that the native army fully automatic charger refused to charge at all. I charged this device so much that I still (since 1995) use this battery (of course, charging it if necessary). Even if only occasionally.
2. A miner's lantern made in 1992, which spent several years in a discharged state on a friend's balcony (with our winters). At the time he was handed over to me in 1997, he showed no signs of life at all. But I still use it when fishing
3. The battery in the first car was rejected by the seller upon purchase (UA9CDV) and was highly recommended for replacement in the first winter, because “he had a lot of trouble with it”... But I drove the car for several years and the third owner is still driving it. Car from 1993.
4. The battery of a friend’s video camera in 2000 did not last even 5 minutes. After the “correct” procedure, he forced the video camera to work for 1 hour, although according to the passport it could only work continuously for 45 minutes and he never managed to do it longer.
I won’t list more, because the page will become sad.
At the same time, it should be noted that the batteries did not “boil” as with the original chargers and did not get so hot.
Terms of use:
1. Use resistor R1 to set the charging current to 1/10 of the battery capacity
2. Use resistor R2 to set the discharge current to 1/10 of the charging current
3. During manual charging, maintain the charging current constant over time. This requirement is desirable, but as far back as I can remember, I have never complied with it. Therefore, the charge current was initially set higher, because it will inevitably decrease significantly (depending on the condition of the battery).
4. Under such conditions, it takes 14-16 hours to charge any battery (from those listed at the beginning).
In the case of Li-on and Li-Pol batteries, the issue is much more difficult to solve: with the use of charging processors and other hardware, however, they do not have memory, so there is an option to bypass various tricks. But I don’t recommend charging them with asymmetrical current (it’s better to use constant current). Although I did it more than once))
Taking into account this experience, I made a third terminal in the transceiver’s power supply, to which I supplied power from the transformer through a diode. Now, by connecting the battery to this terminal and to the negative terminal, I have been charging all my old batteries for almost 10 years. Moreover, the current output is significant!
Significantly better operational features Rechargeable batteries can be achieved if they are charged using an asymmetric volume. The charging device circuit that implements this principle is shown in the figure.
With a good half-cycle of the input alternating voltage, current flows through the elements VD1, R1 and is stabilized by the diode VD2. Part of the stabilized voltage is supplied to the base of transistor VT2 through variable resistor R3. Transistors VT2 and VT4 of the lower side of the device work as a current generator, the value of which depends on the resistance of resistor R4 and the voltage at the base of VT2.
The charging current in the battery circuit flows through the elements VD3, SA1.1, PA1, SA1.2, the battery, and the collector differential of the transistor VT4, R4.
With a negative half-cycle of alternating voltage on diode VD1, the operation of the device is similar, but the upper arm works - VD1 stabilizes the negative voltage, which regulates the current flowing through the battery in reverse voltage (discharge current).
The PA1 milliammeter shown in the diagram is used during initial setup, in the future its possible turn off by moving the toggle switch to the second position.
This Charger has the following advantages: 1. Charging and discharging currents can be adjusted independently of each other. Therefore, in this device it is likely to use rechargeable batteries with different energy capacities. 2. In the event of any loss of alternating voltage, each of the arms is closed and no current flows through the battery, which protects the battery from spontaneous discharge.
In this device, it is possible to use domestic elements as VD1 and VD2 - KC133A, VT1 and VT2 - KT315B or KT503B. The remaining elements are selected depending on the charging current. If it does not exceed 100 mA, then use KG815 or KT807 with any letter indices as transistors VT3 and VT4 (located on a heat sink with a heat-dissipating surface area of 5...15 sq.cm), and as diodes VD3 and VD4 - D226, KD105 also with any letter indices.
Required reading:
Homemade simple desulfator with current control, charging with pulsed current desulfator
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Diagram and description of a homemade charger for charging car batteries with asymmetric current.
Significantly better performance characteristics of batteries can be achieved if they are charged with an asymmetrical current.
A charging device circuit that implements this principle is shown in Figure 1.
Fig.1. Click on the picture to view.
With a positive half-cycle of the input alternating voltage, current flows through the elements VD1, R1 and is stabilized by the diode VD2. Part of the stabilized voltage is supplied to the base of transistor VT2 through variable resistor R3. Transistors VT2 and VT4 of the lower side of the device work as a current generator, the value of which depends on the resistance of resistor R4 and the voltage at the base of VT2. The charging current in the battery circuit flows through the elements VD3, SA1.1, PA1, SA1.2, the battery, and the collector differential of the transistor VT4, R4.
With a negative half-cycle of the alternating voltage on the diode VD1, the operation of the device is similar, but the upper arm works - VD1 stabilizes the negative voltage, which regulates the current flowing through the battery in reverse voltage (discharge current).
The PA1 milliammeter shown in the diagram is used during the initial setup; later it can be turned off by moving the switch to another position.
This charger has the following advantages: 1. Charging and discharging currents can be adjusted independently of each other. Therefore, in this device it is possible to use batteries with different energy capacities. 2. In the event of any loss of alternating voltage, each of the arms is closed and no current flows through the battery, which protects the battery from spontaneous discharge.
In this device, domestic elements can be used as VD1 and VD2 - KC133A, VT1 and VT2 - KT315B or KT503B. The remaining elements are selected depending on the charging current. If it does not exceed 100 mA, then KT815 or KT807 with any letter indices should be used as transistors VT3 and VT4 (placed on a heat sink with a heat-dissipating surface area of 5...15 sq.cm), and diodes VD3 and VD4 - D226 , KD105 also with any letter indices.
Popular charger schemes:
Thanks to this method, it is possible to reduce the charging voltage due to periodic anodic and cathodic polarization of the electrodes. The method consists of cyclically changing the magnitude and direction of the current through the battery electrodes.
I 3 = Q N /10, A And I p = Qn/50, A, (6.48)
The advantage of the method of charging batteries with asymmetric current is that there is no need for CTC, since irreversible sulphitation of the electrodes does not occur.
The absence of excessive gas emission during charging helps to increase the service life of batteries.
At the same time, a complex power supply control circuit is one of the disadvantages of the method,
Low current charging carried out to compensate for the energy lost as a result of self-discharge of a battery that is inoperative.
Charging with low currents (0.025 - 0.1 A) is carried out when the batteries are in storage areas or directly on the equipment, as well as working as a backup power source.
Charging can be carried out in two modes:
At constant current;
At constant voltage.
Charge with small currents of constant value.
For charging, a rectifier device without a voltage stabilizer and a distribution board are used, which provides connection to several different groups of batteries.
The number of batteries in each group depends on the required recharge, which, in turn, is determined by the capacity and technical condition of the battery.
The recharging current is maintained at 0.025 - 0.1 A, depending on the technical condition of the batteries. Thus, one VSA-5A converter can recharge 200 - 300 starter batteries.
Charge with low currents at constant voltage.
For charging, a rectifier with a voltage stabilizer is used, to which the batteries are connected. In order to compensate for self-discharge and prevent partial loss of battery capacity, it is necessary to maintain the voltage within 2.18 - 2.25 V for each battery. The final voltage value depends on the specific battery used.
To determine the specific value of the recharge voltage, the density of the electrolyte in the battery is monitored. If during recharging the density of the electrolyte decreases, this indicates that the self-discharge current exceeds the sub-charge currents. In this case, it is necessary to increase the charging voltage. Otherwise, the batteries may irreversibly lose their electrical capacity.
In Fig. 1 shows a simple charger designed to use the method described above. The circuit provides a pulse charging current of up to 10 A (used for accelerated charging). To restore and train batteries, it is better to set the pulse charging current to 5 A. In this case, the discharge current will be 0.5 A. The discharge current is determined by the value of resistor R4.
Rice. 1 Electrical diagram of the charger.
The circuit is designed in such a way that the battery is charged by current pulses during one half of the period of the mains voltage, when the voltage at the output of the circuit exceeds the voltage at the battery. During the second half-cycle, diodes VD1, VD2 are closed and the battery is discharged through load resistance R4.
The charging current value is set by regulator R2 using an ammeter. Considering that when charging the battery, part of the current also flows through resistor R4 (10%), the readings of ammeter PA1 should correspond to 1.8 A (for a pulse charging current of 5 A), since the ammeter shows the average value of the current over a period of time, and the charge produced during half the period.
The circuit provides protection for the battery from uncontrolled discharge in the event of an accidental loss of mains voltage. In this case, relay K1 with its contacts will open the battery connection circuit. Relay K1 is used of the RPU-0 type with an operating winding voltage of 24 V or a lower voltage, but in this case a limiting resistor is connected in series with the winding.
For the device, you can use a transformer with a power of at least 150 W with a voltage in the secondary winding of 22...25 V.
The PA1 measuring device is suitable with a scale of 0...5 A (0...3 A), for example M42100. Transistor VT1 is installed on a radiator with an area of at least 200 square meters. cm, for which it is convenient to use the metal case of the charger design.
The circuit uses a transistor with a high gain (1000...18000), which can be replaced with KT825 when changing the polarity of the diodes and zener diode, since it has a different conductivity. The last letter in the transistor designation can be anything.
Rice. 2 Electrical diagram of the starting device.
To protect the circuit from accidental short circuit, fuse FU2 is installed at the output.
The resistors used are R1 type C2-23, R2 - PPBE-15, R3 - C5-16MB, R4 - PEV-15, the value of R2 can be from 3.3 to 15 kOhm. Any VD3 zener diode is suitable, with a stabilization voltage from 7.5 to 12 V.
The given circuits of the starting (Fig. 2) and charger devices (Fig. 1) can be easily combined (there is no need to isolate the body of the transistor VT1 from the body of the structure), for which it is enough to wind another winding of approximately 25...30 turns on the starting transformer wire PEV-2 with a diameter of 1.8...2.0 mm.
