The photo shows a homemade automatic charger for charging 12 V car batteries with a current of up to 8 A, assembled in a housing from a B3-38 millivoltmeter.
Why do you need to charge your car battery?
charger
The battery in the car is charged using an electric generator. To protect electrical equipment and devices from the increased voltage generated by a car generator, a relay-regulator is installed after it, which limits the voltage in the car’s on-board network to 14.1 ± 0.2 V. To fully charge the battery, a voltage of at least 14.5 is required IN.
Thus, it is impossible to fully charge the battery from a generator and before the onset of cold weather it is necessary to recharge the battery from a charger.
Analysis of charger circuits
The scheme for making a charger from a computer power supply looks attractive. The structural diagrams of computer power supplies are the same, but the electrical ones are different, and modification requires high radio engineering qualifications.
I was interested in the capacitor circuit of the charger, the efficiency is high, it does not generate heat, it provides a stable charging current regardless of the state of charge of the battery and fluctuations in the supply network, and is not afraid of output short circuits. But it also has a drawback. If during charging the contact with the battery is lost, the voltage on the capacitors increases several times (the capacitors and transformer form a resonant oscillatory circuit with the frequency of the mains), and they break through. It was necessary to eliminate only this one drawback, which I managed to do.
The result was a charger circuit without the above-mentioned disadvantages. For more than 16 years I have been charging any 12 V acid batteries with it. The device works flawlessly.
Schematic diagram of a car charger
Despite its apparent complexity, the circuit of a homemade charger is simple and consists of only a few complete functional units.
If the circuit to repeat seems complicated to you, then you can assemble a more one that works on the same principle, but without the automatic shutdown function when the battery is fully charged.
Current limiter circuit on ballast capacitors
In a capacitor car charger, regulation of the magnitude and stabilization of the battery charge current is ensured by connecting ballast capacitors C4-C9 in series with the primary winding of the power transformer T1. The larger the capacitor capacity, the greater the battery charging current.
In practice, this is a complete version of the charger; you can connect a battery after the diode bridge and charge it, but the reliability of such a circuit is low. If contact with the battery terminals is broken, the capacitors may fail.
The capacitance of the capacitors, which depends on the magnitude of the current and voltage on the secondary winding of the transformer, can be approximately determined by the formula, but it is easier to navigate using the data in the table.
To regulate the current in order to reduce the number of capacitors, they can be connected in parallel in groups. My switching is carried out using a two-bar switch, but you can install several toggle switches.
Protection circuit
from incorrect connection of battery poles
The protection circuit against polarity reversal of the charger in case of incorrect connection of the battery to the terminals is made using relay P3. If the battery is connected incorrectly, the VD13 diode does not pass current, the relay is de-energized, the K3.1 relay contacts are open and no current flows to the battery terminals. When connected correctly, the relay is activated, contacts K3.1 are closed, and the battery is connected to the charging circuit. This reverse polarity protection circuit can be used with any charger, both transistor and thyristor. It is enough to connect it to the break in the wires with which the battery is connected to the charger.
Circuit for measuring current and voltage of battery charging
Thanks to the presence of switch S3 in the diagram above, when charging the battery, it is possible to control not only the amount of charging current, but also the voltage. In the upper position of S3, the current is measured, in the lower position the voltage is measured. If the charger is not connected to the mains, the voltmeter will show the battery voltage, and when the battery is charging, the charging voltage. An M24 microammeter with an electromagnetic system is used as a head. R17 bypasses the head in current measurement mode, and R18 serves as a divider when measuring voltage.
Automatic charger shutdown circuit
when the battery is fully charged
To power the operational amplifier and create a reference voltage, a DA1 type 142EN8G 9V stabilizer chip is used. This microcircuit was not chosen by chance. When the temperature of the microcircuit body changes by 10º, the output voltage changes by no more than hundredths of a volt.
The system for automatically turning off charging when the voltage reaches 15.6 V is made on half of the A1.1 chip. Pin 4 of the microcircuit is connected to a voltage divider R7, R8 from which a reference voltage of 4.5 V is supplied to it. Pin 4 of the microcircuit is connected to another divider using resistors R4-R6, resistor R5 is a tuning resistor to set the operating threshold of the machine. The value of resistor R9 sets the threshold for switching on the charger to 12.54 V. Thanks to the use of diode VD7 and resistor R9, the necessary hysteresis is provided between the switch-on and switch-off voltages of the battery charge.
The scheme works as follows. When connecting a car battery to a charger, the voltage at the terminals of which is less than 16.5 V, a voltage sufficient to open transistor VT1 is established at pin 2 of microcircuit A1.1, the transistor opens and relay P1 is activated, connecting contacts K1.1 to the mains through a block of capacitors the primary winding of the transformer and battery charging begins.
As soon as the charge voltage reaches 16.5 V, the voltage at output A1.1 will decrease to a value insufficient to maintain transistor VT1 in the open state. The relay will turn off and contacts K1.1 will connect the transformer through the standby capacitor C4, at which the charge current will be equal to 0.5 A. The charger circuit will be in this state until the voltage on the battery decreases to 12.54 V. As soon as the voltage will be set equal to 12.54 V, the relay will turn on again and charging will proceed at the specified current. It is possible, if necessary, to disable the automatic control system using switch S2.
Thus, the system of automatic monitoring of battery charging will eliminate the possibility of overcharging the battery. The battery can be left connected to the included charger for at least a whole year. This mode is relevant for motorists who drive only in the summer. After the end of the racing season, you can connect the battery to the charger and turn it off only in the spring. Even if there is a power outage, when it returns, the charger will continue to charge the battery as normal.
The principle of operation of the circuit for automatically turning off the charger in case of excess voltage due to the lack of load collected on the second half of the operational amplifier A1.2 is the same. Only the threshold for completely disconnecting the charger from the supply network is set to 19 V. If the charging voltage is less than 19 V, the voltage at output 8 of the A1.2 chip is sufficient to hold the transistor VT2 in the open state, in which voltage is applied to the relay P2. As soon as the charging voltage exceeds 19 V, the transistor will close, the relay will release contacts K2.1 and the voltage supply to the charger will completely stop. As soon as the battery is connected, it will power the automation circuit, and the charger will immediately return to working condition.
Automatic charger design
All parts of the charger are placed in the housing of the V3-38 milliammeter, from which all its contents have been removed, except for the pointer device. The installation of elements, except for the automation circuit, is carried out using a hinged method.
The housing design of the milliammeter consists of two rectangular frames connected by four corners. There are holes made in the corners with equal spacing, to which it is convenient to attach parts.
The TN61-220 power transformer is secured with four M4 screws on an aluminum plate 2 mm thick, the plate, in turn, is attached with M3 screws to the lower corners of the case. The TN61-220 power transformer is secured with four M4 screws on an aluminum plate 2 mm thick, the plate, in turn, is attached with M3 screws to the lower corners of the case. C1 is also installed on this plate. The photo shows a view of the charger from below.
A 2 mm thick fiberglass plate is also attached to the upper corners of the case, and capacitors C4-C9 and relays P1 and P2 are screwed to it. A printed circuit board is also screwed to these corners, on which an automatic battery charging control circuit is soldered. In reality, the number of capacitors is not six, as in the diagram, but 14, since in order to obtain a capacitor of the required value it was necessary to connect them in parallel. The capacitors and relays are connected to the rest of the charger circuit via a connector (blue in the photo above), which made it easier to access other elements during installation.
A finned aluminum radiator is installed on the outer side of the rear wall to cool the power diodes VD2-VD5. There is also a 1 A Pr1 fuse and a plug (taken from the computer power supply) for supplying power.
The charger's power diodes are secured using two clamping bars to the radiator inside the case. For this purpose, a rectangular hole is made in the rear wall of the case. This technical solution allowed us to minimize the amount of heat generated inside the case and save space. The diode leads and supply wires are soldered onto a loose strip made of foil fiberglass.
The photo shows a view of a homemade charger on the right side. The installation of the electrical circuit is made with colored wires, alternating voltage - brown, positive - red, negative - blue wires. The cross-section of the wires coming from the secondary winding of the transformer to the terminals for connecting the battery must be at least 1 mm 2.
The ammeter shunt is a piece of high-resistance constantan wire about a centimeter long, the ends of which are sealed in copper strips. The length of the shunt wire is selected when calibrating the ammeter. I took the wire from the shunt of a burnt pointer tester. One end of the copper strips is soldered directly to the positive output terminal; a thick conductor coming from the contacts of relay P3 is soldered to the second strip. The yellow and red wires go to the pointer device from the shunt.
Printed circuit board of the charger automation unit
The circuit for automatic regulation and protection against incorrect connection of the battery to the charger is soldered on a printed circuit board made of foil fiberglass.
The photo shows the appearance of the assembled circuit. The printed circuit board design for the automatic control and protection circuit is simple, the holes are made with a pitch of 2.5 mm.
The photo above shows a view of the printed circuit board from the installation side with parts marked in red. This drawing is convenient when assembling a printed circuit board.
The printed circuit board drawing above will be useful when manufacturing it using laser printer technology.
And this drawing of a printed circuit board will be useful when applying current-carrying tracks of a printed circuit board manually.
The scale of the pointer instrument of the V3-38 millivoltmeter did not fit the required measurements, so I had to draw my own version on the computer, print it on thick white paper and glue the moment on top of the standard scale with glue.
Thanks to the larger scale size and calibration of the device in the measurement area, the voltage reading accuracy was 0.2 V.
Wires for connecting the charger to the battery and network terminals
The wires for connecting the car battery to the charger are equipped with alligator clips on one side and split ends on the other side. The red wire is selected to connect the positive terminal of the battery, and the blue wire is selected to connect the negative terminal. The cross-section of the wires for connecting to the battery device must be at least 1 mm 2.
The charger is connected to the electrical network using a universal cord with a plug and socket, as is used to connect computers, office equipment and other electrical appliances.
About Charger Parts
Power transformer T1 is used type TN61-220, the secondary windings of which are connected in series, as shown in the diagram. Since the efficiency of the charger is at least 0.8 and the charging current usually does not exceed 6 A, any transformer with a power of 150 watts will do. The secondary winding of the transformer should provide a voltage of 18-20 V at a load current of up to 8 A. If there is no ready-made transformer, then you can take any suitable power and rewind the secondary winding. You can calculate the number of turns of the secondary winding of a transformer using a special calculator.
Capacitors C4-C9 type MBGCh for a voltage of at least 350 V. You can use capacitors of any type designed to operate in alternating current circuits.
Diodes VD2-VD5 are suitable for any type, rated for a current of 10 A. VD7, VD11 - any pulsed silicon ones. VD6, VD8, VD10, VD5, VD12 and VD13 are any that can withstand a current of 1 A. LED VD1 is any, VD9 I used type KIPD29. A distinctive feature of this LED is that it changes color when the connection polarity is changed. To switch it, contacts K1.2 of relay P1 are used. When charging with the main current, the LED lights up yellow, and when switching to the battery charging mode, it lights up green. Instead of a binary LED, you can install any two single-color LEDs by connecting them according to the diagram below.
The operational amplifier chosen is KR1005UD1, an analogue of the foreign AN6551. Such amplifiers were used in the sound and video unit of the VM-12 video recorder. The good thing about the amplifier is that it does not require bipolar power supply or correction circuits and remains operational at a supply voltage of 5 to 12 V. It can be replaced with almost any similar one. For example, LM358, LM258, LM158 are good for replacing microcircuits, but their pin numbering is different, and you will need to make changes to the printed circuit board design.
Relays P1 and P2 are any for a voltage of 9-12 V and contacts designed for a switching current of 1 A. P3 for a voltage of 9-12 V and a switching current of 10 A, for example RP-21-003. If there are several contact groups in the relay, then it is advisable to solder them in parallel.
Switch S1 of any type, designed to operate at a voltage of 250 V and having a sufficient number of switching contacts. If you don’t need a current regulation step of 1 A, then you can install several toggle switches and set the charging current, say, 5 A and 8 A. If you charge only car batteries, then this solution is completely justified. Switch S2 is used to disable the charge level control system. If the battery is charged with a high current, the system may operate before the battery is fully charged. In this case, you can turn off the system and continue charging manually.
Any electromagnetic head for a current and voltage meter is suitable, with a total deviation current of 100 μA, for example type M24. If there is no need to measure voltage, but only current, then you can install a ready-made ammeter designed for a maximum constant measuring current of 10 A, and monitor the voltage with an external dial tester or multimeter by connecting them to the battery contacts.
Setting up the automatic adjustment and protection unit of the automatic control unit
If the board is assembled correctly and all radio elements are in good working order, the circuit will work immediately. All that remains is to set the voltage threshold with resistor R5, upon reaching which the battery charging will be switched to low current charging mode.
The adjustment can be made directly while charging the battery. But still, it’s better to play it safe and check and configure the automatic control and protection circuit of the automatic control unit before installing it in the housing. To do this, you will need a DC power supply, which has the ability to regulate the output voltage in the range from 10 to 20 V, designed for an output current of 0.5-1 A. As for measuring instruments, you will need any voltmeter, pointer tester or multimeter designed to measure DC voltage, with a measurement limit from 0 to 20 V.
Checking the voltage stabilizer
After installing all the parts on the printed circuit board, you need to apply a supply voltage of 12-15 V from the power supply to the common wire (minus) and pin 17 of the DA1 chip (plus). By changing the voltage at the output of the power supply from 12 to 20 V, you need to use a voltmeter to make sure that the voltage at output 2 of the DA1 voltage stabilizer chip is 9 V. If the voltage is different or changes, then DA1 is faulty.
Microcircuits of the K142EN series and analogues have protection against short circuits at the output, and if you short-circuit its output to the common wire, the microcircuit will enter protection mode and will not fail. If the test shows that the voltage at the output of the microcircuit is 0, this does not always mean that it is faulty. It is quite possible that there is a short circuit between the tracks of the printed circuit board or one of the radio elements in the rest of the circuit is faulty. To check the microcircuit, it is enough to disconnect its pin 2 from the board and if 9 V appears on it, it means that the microcircuit is working, and it is necessary to find and eliminate the short circuit.
Checking the surge protection system
I decided to start describing the operating principle of the circuit with a simpler part of the circuit, which is not subject to strict operating voltage standards.
The function of disconnecting the charger from the mains in the event of a battery disconnection is performed by a part of the circuit assembled on an operational differential amplifier A1.2 (hereinafter referred to as the op-amp).
Operating principle of an operational differential amplifier
Without knowing the operating principle of the op-amp, it is difficult to understand the operation of the circuit, so I will give a brief description. The op-amp has two inputs and one output. One of the inputs, which is designated in the diagram by a “+” sign, is called non-inverting, and the second input, which is designated by a “–” sign or a circle, is called inverting. The word differential op-amp means that the voltage at the output of the amplifier depends on the difference in voltage at its inputs. In this circuit, the operational amplifier is switched on without feedback, in comparator mode – comparing input voltages.
Thus, if the voltage at one of the inputs remains unchanged, and at the second it changes, then at the moment of passing through the point of equality of voltages at the inputs, the voltage at the output of the amplifier will change abruptly.
Testing the Surge Protection Circuit
Let's return to the diagram. The non-inverting input of amplifier A1.2 (pin 6) is connected to a voltage divider assembled across resistors R13 and R14. This divider is connected to a stabilized voltage of 9 V and therefore the voltage at the point of connection of the resistors never changes and is 6.75 V. The second input of the op-amp (pin 7) is connected to the second voltage divider, assembled on resistors R11 and R12. This voltage divider is connected to the bus through which the charging current flows, and the voltage on it changes depending on the amount of current and the state of charge of the battery. Therefore, the voltage value at pin 7 will also change accordingly. The divider resistances are selected in such a way that when the battery charging voltage changes from 9 to 19 V, the voltage at pin 7 will be less than at pin 6 and the voltage at the op-amp output (pin 8) will be more than 0.8 V and close to the op-amp supply voltage. The transistor will be open, voltage will be supplied to the winding of relay P2 and it will close contacts K2.1. The output voltage will also close diode VD11 and resistor R15 will not participate in the operation of the circuit.
As soon as the charging voltage exceeds 19 V (this can only happen if the battery is disconnected from the output of the charger), the voltage at pin 7 will become greater than at pin 6. In this case, the voltage at the op-amp output will abruptly decrease to zero. The transistor will close, the relay will de-energize and contacts K2.1 will open. The supply voltage to the RAM will be interrupted. At the moment when the voltage at the output of the op-amp becomes zero, diode VD11 opens and, thus, R15 is connected in parallel to R14 of the divider. The voltage at pin 6 will instantly decrease, which will eliminate false positives when the voltages at the op-amp inputs are equal due to ripple and interference. By changing the value of R15, you can change the hysteresis of the comparator, that is, the voltage at which the circuit will return to its original state.
When the battery is connected to the RAM, the voltage at pin 6 will again be set to 6.75 V, and at pin 7 it will be less and the circuit will begin to operate normally.
To check the operation of the circuit, it is enough to change the voltage on the power supply from 12 to 20 V and connect a voltmeter instead of relay P2 to observe its readings. When the voltage is less than 19 V, the voltmeter should show a voltage of 17-18 V (part of the voltage will drop across the transistor), and if it is higher, zero. It is still advisable to connect the relay winding to the circuit, then not only the operation of the circuit will be checked, but also its functionality, and by the clicks of the relay it will be possible to control the operation of the automation without a voltmeter.
If the circuit does not work, then you need to check the voltages at inputs 6 and 7, the op-amp output. If the voltages differ from those indicated above, you need to check the resistor values of the corresponding dividers. If the divider resistors and diode VD11 are working, then, therefore, the op-amp is faulty.
To check the circuit R15, D11, it is enough to disconnect one of the terminals of these elements; the circuit will work, only without hysteresis, that is, it turns on and off at the same voltage supplied from the power supply. Transistor VT12 can be easily checked by disconnecting one of the R16 pins and monitoring the voltage at the output of the op-amp. If the voltage at the output of the op-amp changes correctly, and the relay is always on, it means that there is a breakdown between the collector and emitter of the transistor.
Checking the battery shutdown circuit when it is fully charged
The operating principle of op amp A1.1 is no different from the operation of A1.2, with the exception of the ability to change the voltage cutoff threshold using trimming resistor R5.
To check the operation of A1.1, the supply voltage supplied from the power supply smoothly increases and decreases within 12-18 V. When the voltage reaches 15.6 V, relay P1 should turn off and contacts K1.1 switch the charger to low current charging mode through a capacitor C4. When the voltage level drops below 12.54 V, the relay should turn on and switch the charger into charging mode with a current of a given value.
The switching threshold voltage of 12.54 V can be adjusted by changing the value of resistor R9, but this is not necessary.
Using switch S2, it is possible to disable the automatic operating mode by turning on relay P1 directly.
Capacitor charger circuit
without automatic shutdown
For those who do not have sufficient experience in assembling electronic circuits or do not need to automatically turn off the charger after charging the battery, I offer a simplified version of the circuit diagram for charging acid-acid car batteries. A distinctive feature of the circuit is its ease of repetition, reliability, high efficiency and stable charging current, protection against incorrect battery connection, and automatic continuation of charging in the event of a loss of supply voltage.
The principle of stabilizing the charging current remains unchanged and is ensured by connecting a block of capacitors C1-C6 in series with the network transformer. To protect against overvoltage on the input winding and capacitors, one of the pairs of normally open contacts of relay P1 is used.
When the battery is not connected, the contacts of relays P1 K1.1 and K1.2 are open and even if the charger is connected to the power supply, no current flows to the circuit. The same thing happens if you connect the battery incorrectly according to polarity. When the battery is connected correctly, the current from it flows through the VD8 diode to the winding of relay P1, the relay is activated and its contacts K1.1 and K1.2 are closed. Through closed contacts K1.1, the mains voltage is supplied to the charger, and through K1.2 the charging current is supplied to the battery.
At first glance, it seems that relay contacts K1.2 are not needed, but if they are not there, then if the battery is connected incorrectly, current will flow from the positive terminal of the battery through the negative terminal of the charger, then through the diode bridge and then directly to the negative terminal of the battery and diodes the charger bridge will fail.
The proposed simple circuit for charging batteries can be easily adapted to charge batteries at a voltage of 6 V or 24 V. It is enough to replace relay P1 with the appropriate voltage. To charge 24-volt batteries, it is necessary to provide an output voltage from the secondary winding of transformer T1 of at least 36 V.
If desired, the circuit of a simple charger can be supplemented with a device for indicating charging current and voltage, turning it on as in the circuit of an automatic charger.
How to charge a car battery
automatic homemade memory
Before charging, the battery removed from the car must be cleaned of dirt and its surfaces wiped with an aqueous solution of soda to remove acid residues. If there is acid on the surface, then the aqueous soda solution foams.
If the battery has plugs for filling acid, then all the plugs must be unscrewed so that the gases formed in the battery during charging can escape freely. It is imperative to check the electrolyte level, and if it is less than required, add distilled water.
Next, you need to set the charge current using switch S1 on the charger and connect the battery, observing the polarity (the positive terminal of the battery must be connected to the positive terminal of the charger) to its terminals. If switch S3 is in the down position, the arrow on the charger will immediately show the voltage the battery is producing. All you have to do is plug the power cord into the socket and the battery charging process will begin. The voltmeter will already begin to show the charging voltage.
Automatic devices are simple in design, but very reliable in operation. Their design was created using a simple design without unnecessary electronic additions. They are designed for simple charging of batteries of any vehicles.
Pros:
- The charger will last for many years with proper use and proper maintenance.
Minuses:
- Lack of any protection.
- Eliminating discharge mode and the possibility of reconditioning the battery.
- Heavy weight.
- Quite a high cost.
The classic charger consists of the following key elements:
- Transformer.
- Rectifier.
- Adjustment block.
Such a device produces direct current at a voltage of 14.4V, not 12V. Therefore, according to the laws of physics, it is impossible to charge one device with another if they have the same voltage. Based on the above, the optimal value for such a device is 14.4 Volts.
The key components of any charger are:
- transformer;
- mains plug;
- fuse (provides short circuit protection);
- wire rheostat (adjusts the charging current);
- ammeter (shows the strength of electric current);
- rectifier (converts alternating current to direct current);
- rheostat (regulates current and voltage in the electrical circuit);
- bulb;
- switch;
- frame;
Wires for connection
To connect any charger, as a rule, red and black wires are used, red is positive, black is negative.
When choosing cables to connect a charger or starting device, you must select a cross-section of at least 1 mm2.
Attention. Further information is provided for informational purposes only. Whatever you want to bring to life, you do at your own discretion. Incorrect or inept handling of certain spare parts and devices will cause them to malfunction.
Having looked at the available types of chargers, let’s move on directly to making them ourselves.
Charging the battery from the computer power supply
To charge any battery, 5-6 ampere hours is enough, this is about 10% of the capacity of the entire battery. Any power supply with a capacity of 150 W or more can produce it.
So, let's look at 2 ways to make your own charger from a computer power supply.
Method one
For manufacturing you need the following parts:
- power supply, power from 150 W;
- resistor 27 kOhm;
- current regulator R10 or resistor block;
- wires with a length of 1 meter;
Work progress:
- To start we will need to disassemble the power supply.
- We extract wires we do not use, namely -5v, +5v, -12v and +12v.
- We replace the resistor R1 to a pre-prepared 27 kOhm resistor.
- Removing the wires 14 and 15, and 16 we simply turn off.
- From the block We bring out the power cord and wires to the battery.
- Install the current regulator R10. In the absence of such a regulator, you can make a homemade resistor block. It will consist of two 5 W resistors, which will be connected in parallel.
- To set up the charger, We install a variable resistor in the board.
- To exits 1,14,15,16 We solder the wires and use a resistor to set the voltage to 13.8-14.5V.
- At the end of the wires connect the terminals.
- We delete the remaining unnecessary tracks.
Important: adhere to the complete instructions, the slightest deviation can lead to burnout of the device.
Method two
To manufacture our device using this method, you will need a slightly more powerful power supply, namely 350 W. Since it can output 12-14 amps which will satisfy our needs.
Work progress:
- In computer power supplies The pulse transformer has several windings, one of them is 12V, and the second is 5V. To make our device, you only need a 12V winding.
- To start our block you will need to find the green wire and connect it to the black wire. If you use a cheap Chinese unit, there may be a gray wire instead of a green one.
- If you have an old power supply and with a power button, the above procedure is not needed.
- Further, we make 2 thick busbars from the yellow and black wires, and cut off the unnecessary wires. A black tire will be a minus, a yellow one will be a plus.
- To improve reliability Our device can be swapped. The fact is that the 5V bus has a more powerful diode than the 12V.
- Since the power supply has a built-in fan, then he is not afraid of overheating.
Method three
For manufacturing we will need the following parts:
- power supply, power 230 W;
- board with TL 431 chip;
- resistor 2.7 kOhm;
- resistor 200 Ohm power 2 W;
- 68 Ohm resistor with a power of 0.5 W;
- resistor 0.47 Ohm power 1 W;
- 4-pin relay;
- 2 diodes 1N4007 or similar diodes;
- resistor 1kOhm;
- bright LED;
- wire length of at least 1 meter and cross-section of at least 2.5 mm 2, with terminals;
Work progress:
- Desoldering all wires except 4 black and 2 yellow wires, since they carry power.
- Close the contacts with a jumper, responsible for overvoltage protection so that our power supply does not turn off due to overvoltage.
- We replace it on a board with a TL 431 chip built-in resistor for a 2.7 kOhm resistor, to set the output voltage to 14.4 V.
- Add a 200 Ohm resistor with a power of 2 W per output from the 12V channel, to stabilize the voltage.
- Add a 68 Ohm resistor with a power of 0.5 W per output from the 5V channel, to stabilize the voltage.
- Solder the transistor on the board with the TL 431 chip, to eliminate obstacles when setting the voltage.
- Replace the standard resistor, in the primary circuit of the transformer winding, to a 0.47 Ohm resistor with a power of 1 W.
- Assembling a protection scheme from incorrect connection to the battery.
- Unsolder from the power supply unnecessary parts.
- We output necessary wires from the power supply.
- Solder the terminals to the wires.
For ease of use of the charger, connect an ammeter.
The advantage of such a homemade device is the inability to recharge the battery.
The simplest device using an adapter
cigarette lighter adapter Now consider the case when there is no unnecessary power supply available, our battery is dead and needs to be charged.
Every good owner or fan of all kinds of electronic devices has an adapter for recharging autonomous equipment. Any 12V adapter can be used to charge a car battery.
The main condition for such charging is that the voltage supplied by the source is no less than that of the battery.
Work progress:
- Necessary cut off the connector from the end of the adapter wire and peel off the insulation at least 5 cm.
- Since the wire goes double, it is necessary to divide it. The distance between the ends of the 2 wires must be at least 50 cm.
- Solder or tape to the ends of the terminal wire for secure fixation on the battery.
- If the terminals are the same, then you need to take care of putting insignia on them.
- The biggest disadvantage of this method consists of constant monitoring of the temperature of the adapter. Since if the adapter burns out, it can render the battery unusable.
Before connecting the adapter to the network, you must first connect it to the battery.
Charger made from a diode and a household light bulb
Diode is a semiconductor electronic device that is capable of conducting current in one direction and has a resistance equal to zero.
The charging adapter for the laptop will be used as a diode.
To manufacture this type of device, we will need:
- charging adapter for laptop;
- bulb;
- wires from 1 m long;
Each car charger produces about 20V voltage. Since the diode replaces the adapter and passes voltage only in one direction, it is protected from short circuits that can occur if connected incorrectly.
The higher the power of the light bulb, the faster the battery charges.
Work progress:
- To the positive wire of the laptop adapter We connect our light bulb.
- From a light bulb we throw the wire to the positive.
- Disadvantage from the adapter directly connect to the battery.
If connected correctly, our light bulb will glow because the current at the terminals is low and the voltage is high.
Also, you need to remember that proper charging requires an average current of 2-3 amperes. Connecting a high-power light bulb leads to an increase in current strength, and this, in turn, has a detrimental effect on the battery.
Based on this, you can connect a high-power light bulb only in special cases.
This method involves constantly monitoring and measuring the voltage at the terminals. Overcharging the battery will produce excessive amounts of hydrogen and may damage it.
When charging the battery in this way, try to stay near the device, since leaving it temporarily unattended can lead to failure of the device and the battery.
Checking and setting
To test our device, you must have a working car light bulb. First, using a wire, we connect our light bulb to the charger, remembering to observe the polarity. We plug in the charger and the light comes on. Everything is working.
Each time, before using a homemade charging device, check its functionality. This check will eliminate all possibilities of damaging your battery.
How to charge a car battery
Quite a large number of car owners consider charging the battery a very simple matter.
But in this process there are a number of nuances on which the long-term operation of the battery depends:
Before you put the battery on charge, you need to carry out a number of necessary actions:
- Use chemical resistant gloves and goggles.
- After removing the battery carefully inspect it for signs of mechanical damage and traces of liquid leakage.
- Unscrew the protective caps, to release the generated hydrogen, to avoid boiling the battery.
- Take a close look at the liquid. It should be transparent, without flakes. If the liquid is dark in color and there are signs of sediment, seek professional help immediately.
- Check fluid level. Based on current standards, there are marks on the side of the battery, “minimum and maximum,” and if the fluid level is below the required level, it must be refilled.
- Flood Only distilled water is needed.
- Don't turn it on charger into the network until the crocodiles are connected to the terminals.
- Observe polarity when connecting alligator clips to the terminals.
- If during charging If you hear boiling sounds, then unplug the device, let the battery cool down, check the fluid level and then you can reconnect the charger to the network.
- Make sure that the battery is not overcharged, since the condition of its plates depends on this.
- Charge the battery only in well-ventilated areas, as toxic substances are released during the charging process.
- Electrical network must have installed circuit breakers that turn off the network in the event of a short circuit.
After you charge the battery, over time the current will drop and the voltage at the terminals will increase. When the voltage reaches 14.5V, charging should be stopped by disconnecting from the network. When the voltage reaches more than 14.5 V, the battery will begin to boil and the plates will become free of liquid.
Analysis of more than 11 circuits for making a charger with your own hands at home, new circuits for 2017 and 2018, how to assemble a circuit diagram in an hour.
TEST:
To understand whether you have the necessary information about batteries and chargers for them, you should take a short test:- What are the main reasons why a car battery discharges on the road?
A) The motorist got out of the vehicle and forgot to turn off the headlights.
B) The battery has become too hot due to exposure to sunlight.
- Can the battery fail if the car is not used for a long time (sitting in a garage without starting)?
A) If left idle for a long time, the battery will fail.
B) No, the battery will not deteriorate, it will only need to be charged and it will function again.
- What current source is used to recharge the battery?
A) There is only one option - a network with a voltage of 220 volts.
B) 180 Volt network.
- Is it necessary to remove the battery when connecting a homemade device?
A) It is advisable to remove the battery from its installed location, otherwise there is a risk of damaging the electronics due to high voltage.
B) It is not necessary to remove the battery from its installed location.
- If you confuse “minus” and “plus” when connecting a charger, will the battery fail?
A) Yes, if connected incorrectly, the equipment will burn out.
B) The charger simply will not turn on; you will need to move the necessary contacts to the correct places.
Answers:
- A) Headlights not turned off when stopping and sub-zero temperatures are the most common causes of battery discharge on the road.
- A) The battery fails if it is not recharged for a long time when the car is idle.
- A) For recharging, a mains voltage of 220 V is used.
- A) It is not advisable to charge the battery with a homemade device if it is not removed from the car.
- A) The terminals should not be mixed up, otherwise the homemade device will burn out.
Battery on vehicles require periodic charging. The reasons for the discharge can be different - from headlights that the owner forgot to turn off, to negative temperatures outside in winter. For recharge battery You will need a good charger. This device is available in large varieties in auto parts stores. But if there is no opportunity or desire to purchase, then memory You can do it yourself at home. There are also a large number of schemes - it is advisable to study them all in order to choose the most suitable option.
Definition: A car charger is designed to transmit electric current with a given voltage directly to Battery
Answers to 5 Frequently Asked Questions
- Will I need to take any additional measures before charging the battery in my car?– Yes, you will need to clean the terminals, since acid deposits appear on them during operation. Contacts It needs to be cleaned very well so that current flows to the battery without difficulty. Sometimes motorists use grease to treat terminals; this should also be removed.
- How to wipe charger terminals?— You can buy a specialized product in a store or prepare it yourself. Water and soda are used as a self-made solution. The components are mixed and stirred. This is an excellent option for treating all surfaces. When the acid comes into contact with soda, a reaction will occur and the motorist will definitely notice it. This area will need to be thoroughly wiped to get rid of all acids. If the terminals were previously treated with grease, it can be removed with any clean rag.
- If there are covers on the battery, do they need to be opened before charging?— If there are covers on the body, they must be removed.
- Why is it necessary to unscrew the battery caps?— This is necessary so that the gases formed during the charging process can freely exit the case.
- Is there a need to pay attention to the electrolyte level in the battery?- This is done without fail. If the level is lower than required, then you need to add distilled water inside the battery. Determining the level is not difficult - the plates must be completely covered with liquid.
It’s also important to know: 3 nuances about operation
The homemade product differs somewhat in its method of operation from the factory version. This is explained by the fact that the purchased unit has built-in functions, helping in work. They are difficult to install on a device assembled at home, and therefore you will have to adhere to several rules when operation.
- A self-assembled charger will not turn off when the battery is fully charged. That is why it is necessary to periodically monitor the equipment and connect it to multimeter– for charge control.
- You need to be very careful not to confuse “plus” and “minus”, otherwise Charger will burn.
- The equipment must be turned off when connecting to charger.
By following these simple rules, you will be able to recharge correctly battery and avoid unpleasant consequences.
Top 3 charger manufacturers
If you don’t have the desire or ability to assemble it yourself memory, then pay attention to the following manufacturers:
- Stack.
- Sonar.
- Hyundai.
How to avoid 2 mistakes when charging a battery
It is necessary to follow the basic rules in order to properly nourish battery by car.
- Direct to mains battery connection is prohibited. Chargers are intended for this purpose.
- Even device it is made with high quality and from good materials, you will still need to periodically monitor the process charging, so that troubles don't happen.
Following simple rules will ensure reliable operation of self-made equipment. It is much easier to monitor the unit than to spend money on components for repairs.
The simplest battery charger
Scheme of a 100% working 12 volt charger
Look at the picture for the diagram memory at 12 V. The equipment is intended for charging car batteries with a voltage of 14.5 Volts. The maximum current received during charging is 6 A. But the device is also suitable for other batteries - lithium-ion, since the voltage and output current can be adjusted. All the main components for assembling the device can be found on the Aliexpress website.
Required components:
- dc-dc buck converter.
- Ammeter.
- Diode bridge KVRS 5010.
- Hubs 2200 uF at 50 volts.
- transformer TS 180-2.
- Circuit breakers.
- Plug for connecting to the network.
- "Crocodiles" for connecting terminals.
- Radiator for diode bridge.
Transformer any one can be used at your own discretion. The main thing is that its power is not lower than 150 W (with a charging current of 6 A). It is necessary to install thick and short wires on the equipment. The diode bridge is fixed on a large radiator.
Look at the picture of the charger circuit Dawn 2. It is compiled according to the original Memory If you master this scheme, you will be able to independently create a high-quality copy that is no different from the original sample. Structurally, the device is a separate unit, closed with a housing to protect the electronics from moisture and exposure to bad weather conditions. It is necessary to connect a transformer and thyristors on the radiators to the base of the case. You will need a board that will stabilize the current charge and control the thyristors and terminals.
1 smart memory circuit
Look at the picture for a circuit diagram of a smart charger. The device is necessary for connection to lead-acid batteries with a capacity of 45 amperes per hour or more. This type of device is connected not only to batteries that are used daily, but also to those on duty or in reserve. This is a fairly budget version of the equipment. It does not provide indicator, and you can buy the cheapest microcontroller.
If you have the necessary experience, then you can assemble the transformer yourself. There is also no need to install audible warning signals - if battery connects incorrectly, the discharge lamp will light up to indicate an error. The equipment must be equipped with a switching power supply of 12 volts - 10 amperes.
1 industrial memory circuit
Look at the industrial diagram charger from Bars 8A equipment. Transformers are used with one 16-volt power winding, several vd-7 and vd-8 diodes are added. This is necessary in order to provide a bridge rectifier circuit from one winding.
1 inverter device diagram
Look at the picture for a diagram of an inverter charger. This device discharges the battery to 10.5 Volts before charging. The current is used with a value of C/20: “C” indicates the capacity of the installed battery. After that process the voltage rises to 14.5 Volts using a discharge-charge cycle. The ratio of charge and discharge is ten to one.
1 electrical circuit charger electronics
1 powerful memory circuit
Look at the picture at the diagram of a powerful charger for a car battery. The device is used for acidic battery, having high capacity. The device easily charges a car battery with a capacity of 120 A. The output voltage of the device is self-regulated. It ranges from 0 to 24 volts. Scheme It is notable for the fact that it has few components installed, but it does not require additional settings during operation.
Many could already see the Soviet Charger. It looks like a small metal box and may seem quite unreliable. But this is not true at all. The main difference between the Soviet model and modern models is reliability. The equipment has structural capacity. In the event that to the old device connect the electronic controller, then charger it will be possible to revive. But if you no longer have one at hand, but there is a desire to assemble it, you need to study the diagram.
To the features their equipment includes a powerful transformer and rectifier, with the help of which it is possible to quickly charge even a very discharged battery. Many modern devices will not be able to reproduce this effect.
Electron 3M
In an hour: 2 DIY charging concepts
Simple circuits
1 the simplest scheme for an automatic charger for a car battery
A high-quality car battery cannot be overestimated. However, over time it becomes less capacious and can discharge faster. This process is also influenced by other factors related to operating conditions. To avoid getting into a difficult situation, it is worth having a simple DIY charger at home or in the garage.
In most cases, the circuit diagram of a homemade charger will be relatively simple. It will be possible to assemble such a device from available inexpensive components. At the same time, the electric unit will help to quickly start the car. It is preferable to acquire starting-charging equipment, but it requires a little more power from the elements used.
It is necessary to use electric recharge for the battery in situations where measurements at the terminals of an electrical device show a level below 11.2 V for most passenger cars. Although the engine is able to start at this voltage level, unwanted chemical processes begin inside. Sulfation and destruction of the plates occurs. The capacity is noticeably reduced.
It is important to know that during a long winter or parking a car for several weeks, the charge level drops, so it is recommended to monitor this value with a multimeter, and if necessary, use a self-made charger for car batteries or purchased at a car store.
To recharge the battery, two types of devices are most often used:
- DC voltage output on “crocodiles”;
- systems with pulse type of operation.
When charging from a constant current device, the charge current value is selected arithmetically corresponding to 1/10 of the capacity value set by the manufacturer. When a 60 A*h battery is available, the output amperage should be at the level of 6 A. It is worth considering studies according to which a moderate reduction in the number of output amperes helps to reduce sulfation processes.
If the plates become partially covered with unwanted sulfate deposits, then experienced motorists will use desulfation operations. The methodology used is as follows:
- We discharge the battery until 3-5 V appears on the multimeter after measurement, using large currents and a short duration of their influence for the operation, for example, cranking with a starter;
- at the next stage, we slowly fully charge the unit from a one-amp source;
- previous operations are repeated for 7-10 cycles.
A similar operating principle is used in factory pulse-type charging desulfating devices. During one cycle, a short-term pulse of reverse polarity is received at the battery terminals within a few milliseconds, followed by direct polarity.
It is necessary to monitor the condition of the device and prevent overcharging of the battery. When the values of 12.8-13.2 V are reached at the contacts, it is worth disconnecting the system from the make-up. Otherwise, a boiling phenomenon will occur, an increase in the concentration and density of the electrolyte poured inside and subsequent destruction of the plates. To prevent negative phenomena, the factory circuit diagram of the charger is equipped with electronic control and automatic shutdown boards.
What is the circuit of a car charger?
In a garage environment, you can use several types of car chargers. They can be as primitive as possible, consisting of several elements, or rather bulky multifunctional stationary devices. Typically, car owners follow the path of simplification.
The simplest schemes
If there is no factory charger available, and you need to revive the battery without delay, then the simplest option will do. It involves a limiting resistance in the form of a load and a power source capable of generating 12-25 V.
You can even assemble a homemade charger on your knees if you have a laptop charger in the house. They usually output about 19 V and 2 A. When assembling, it is worth considering the polarity:
- external contact – minus;
- internal contact is a plus.
Important! A limiting resistance must be installed, which is often used as a light bulb from the interior.
It is not worth unscrewing the lamp from the turn signal or even the “stops”, as they will become an overload for the circuit. The circuit consists of the following interconnected elements: negative terminal of the laptop unit - lamp - negative terminal of the charging battery - positive terminal of the charging battery - plus of the laptop unit. An hour and a half to two hours is enough to bring the battery back to life enough so that you can start the engine from it.
If you don’t have laptops or netbooks, we recommend going to the radio market in advance for a powerful diode designed for a reverse voltage of more than 1000 V and a current of more than 3 A. The small dimensions of the part allow you to carry it with you in the glove compartment or trunk so as not to end up in an undesirable position.
You can use such a diode in a homemade circuit. First, we fold it back and take out the battery. At the next stage, we assemble a chain of elements: the first contact of a household outlet in the apartment - the negative contact on the diode - the positive contact of the diode - the limiting load - the negative terminal of the battery - plus the battery - the second contact of the household outlet.
The limiting load in such an assembly is usually a powerful incandescent lamp. It is preferable to choose them from 100 W. The resulting current can be determined from the school formula:
U * I = W, Where
- U – voltage, V;
- I – current strength, A;
- W – power, kW.
Based on calculations, at a 100-watt load and 220-volt voltage, power output is limited to approximately half an ampere. Overnight the battery will receive about 5 A, which will ensure the engine starts. You can triple the power and at the same time speed up charging by adding a couple more of these lamps to the circuit. You should not overdo it and connect powerful consumers such as an electric stove to such a system, as you can damage the diode and battery.
It is important to know that the assembled direct-charging circuit of a car charger with your own hands is recommended for use as a last resort, if there is no other way out.
Remaking a computer power supply
Before starting experiments with electrical appliances, you need to objectively assess your own strengths in implementing the planned design option. Afterwards you can start assembling.
First of all, the selection of material resources is carried out. Often old computer systems are used for this purpose. The power supply is removed from them. Traditionally, they are equipped with leads of different voltages. In addition to the five-volt contacts, there are 12 V taps. The latter are also endowed with a current of 2 A. Such parameters are almost enough to assemble a circuit with your own hands.
We recommend raising the voltage to 15 V. This is often done empirically. To adjust, you will need a kilo-ohm resistance. Such a resistor is placed in parallel with other existing resistors in the block near the eight-legged microcircuit in the secondary circuit of the power supply unit.
Using a similar method, the value of the feedback circuit transmission coefficient is changed, which affects the output voltage. The method usually provides a rise to 13.5 V, which is enough for simple tasks with a car battery.
Crocodile pins are placed on the output contacts. There is no need to install additional limiting protections, since there are limiting electronics inside.
Transformer circuit
Due to its availability, reliability and simplicity, it has long been in demand among experienced drivers. It uses transformers with a secondary winding that produces 12-18 V. Such elements are found in old televisions, tape recorders and other household appliances. Among more modern devices, we can recommend used uninterruptible power supplies. They are available on the secondary market for a small fee.
The most minimalistic version of the scheme contains the following set:
- diode rectifying bridge;
- transformer selected according to parameters;
- protective load calculated according to the network.
Since a large current flows through the limiting load, this causes it to overheat. To balance the amperage without allowing the charging current to exceed, a capacitor is added to the circuit. Its place is the primary circuit of the transformer.
In extreme situations, with a properly calculated capacitor volume, you can take a chance and remove the transformer. However, such a circuit will become unsafe in terms of electric shock.
Optimal circuits can be called those in which there is adjustment of parameters and limiting of the charge current. We present one example on the page.
It will be possible to obtain a diode bridge with minimal effort from a failed car generator. It is enough to unsolder it and reconnect it if necessary.
Basic safety when assembling and operating circuits
When working on assembling a charger for a car battery, it is worth considering certain factors:
- everything must be assembled and installed on a fireproof site;
- when working with direct-flow primitive chargers, you need to arm yourself with means of protection against electric shock: rubber gloves and a mat;
- in the process of charging the battery for the first time with homemade devices, it is necessary to monitor the current state of the operating system;
- control points are the current strength and voltage at the charging output, the permissible degree of heating of the battery and charger, and preventing the electrolyte from boiling;
- If you leave the equipment overnight, it is important to equip the circuit with a residual current device.
Important! A powder fire extinguisher should always be nearby to prevent the fire from spreading.
The steady trend in the development of portable electronics almost every day forces the average user to deal with charging the batteries of their mobile devices. Whether you are the owner of a mobile phone, tablet, laptop or even a car, one way or another you will repeatedly have to deal with charging the batteries of these devices. Today, the market for choosing chargers is so vast and large that in this variety it is quite difficult to make a competent and correct choice of a charger suitable for the type of battery used. In addition, today there are more than 20 types of batteries with different chemical compositions and bases. Each of them has its own specific charge and discharge operation. Due to economic benefits, modern production in this area is now concentrated primarily on the production of lead-acid (gel) (Pb), nickel-metal-hydride (NiMH), nickel-cadmium (NiCd) batteries and lithium-based batteries - lithium-ion ( Li-ion) and lithium-polymer (Li-polymer). The latter of these, by the way, are actively used in powering portable mobile devices. Mainly, lithium batteries have earned popularity due to the use of relatively inexpensive chemical components, a large number of recharge cycles (up to 1000), high specific energy, low degree of self-discharge, and the ability to hold capacity at negative temperatures.
The electrical circuit of the charger for lithium batteries used in mobile gadgets boils down to providing them with a constant voltage during charging, which exceeds the nominal voltage by 10–15%. For example, if a 3.7 V lithium-ion battery is used to power a mobile phone, then to charge it you need a stabilized power source of sufficient power to maintain the charge voltage no higher than 4.2 V - 5 V. That is why most portable chargers that come with the device are designed for a nominal voltage of 5V, determined by the maximum voltage of the processor and battery charge, taking into account the built-in stabilizer.
Of course, you shouldn’t forget about the charge controller, which takes care of the main algorithm for charging the battery, as well as polling its status. Modern lithium batteries produced for mobile devices with low current consumption already come with a built-in controller. The controller performs the function of limiting the charge current depending on the current capacity of the battery, turns off the voltage supply to the device in the event of a critical battery discharge, and protects the battery in the event of a load short circuit (lithium batteries are very sensitive to high load current and tend to get very hot and even explode). For the purpose of unification and interchangeability of lithium-ion batteries, back in 1997, Duracell and Intel developed a control bus for polling the status of the controller, its operation and charge, called SMBus. Drivers and protocols were written for this bus. Modern controllers still use the basics of the charging algorithm prescribed by this protocol. In terms of technical implementation, there are many microcircuits that can implement charge control of lithium batteries. Among them, the MCP738xx series, MAX1555 from MAXIM, STBC08 or STC4054 with a built-in protective n-channel MOSFET transistor, a charge current detection resistor and a controller supply voltage range from 4.25 to 6.5 Volts stand out. At the same time, in the latest microcircuits from STMicroelectronics, the battery charge voltage value of 4.2 V has a spread of only +/- 1%, and the charging current can reach 800 mA, which will allow charging batteries with a capacity of up to 5000 mAh.
Considering the charging algorithm for lithium-ion batteries, it is worth saying that this is one of the few types that provide the certified ability to charge with a current of up to 1C (100% of the battery capacity). Thus, a battery with a capacity of 3000 mAh can be charged with a current of up to 3A. However, frequent charging with a large “shock” current, although it will significantly reduce its time, will at the same time quite quickly reduce the battery capacity and render it unusable. From the experience of designing electrical circuits for chargers, we will say that the optimal charging value for a lithium-in (polymer) battery is 0.4C - 0.5C of its capacity.
A current value of 1C is allowed only at the moment of initial battery charging, when the battery capacity reaches approximately 70% of its maximum value. An example would be the charging of a smartphone or tablet, when the initial restoration of capacity occurs in a short time, and the remaining percentages accumulate slowly.
In practice, quite often the effect of deep discharge of a lithium battery occurs when its voltage drops below 5% of its capacity. In this case, the controller is not able to provide sufficient starting current to build up the initial charge capacity. (This is why it is not recommended to discharge such batteries below 10%). To solve such situations, you need to carefully disassemble the battery and turn off the built-in charge controller. Next, you need to connect an external charge source to the battery terminals, capable of delivering a current of at least 0.4C of the battery capacity and a voltage of no higher than 4.3V (for 3.7V batteries). The electrical circuit of the charger for the initial stage of charging such batteries can be used from the example below.
This circuit consists of a 1A current stabilizer. (set by resistor R5) on the parametric stabilizer LM317D2T and the switching voltage regulator LM2576S-adj. The stabilization voltage is determined by feedback to the 4th leg of the voltage stabilizer, that is, the ratio of resistances R6 and R7, which set the maximum battery charging voltage at idle. The transformer must produce 4.2 - 5.2 V alternating voltage on the secondary winding. Then, after stabilization, we will receive 4.2 - 5V DC voltage, sufficient to charge the above-mentioned battery.
Nickel - metal - hydride batteries (NiMH) can most often be found in standard battery housings - this is the form factor AAA (R03), AA (R6), D, C, 6F22 9V. The electrical circuit of the charger for NiMH and NiCd batteries must include the following functionality related to the specific charging algorithm of this type of battery.
Different batteries (even with the same parameters) change their chemical and capacitive characteristics over time. As a result, it becomes necessary to organize the charging algorithm for each instance individually, since during the charging process (especially with high currents, which nickel batteries allow), excessive overcharging affects the rapid overheating of the battery. Temperatures during charging above 50 degrees due to chemically irreversible decomposition processes of nickel will completely destroy the battery. Thus, the electrical circuit of the charger must have the function of monitoring the temperature of the battery. To increase the service life and the number of recharge cycles of a nickel battery, it is advisable to discharge each cell to a voltage of at least 0.9V. current of about 0.3C from its capacity. For example, a battery with 2500 – 2700 mAh. Discharge the active load with a current of 1A. Also, the charger must support “training” charging, when a cyclic discharge to 0.9V occurs over several hours, followed by charging with a current of 0.3 - 0.4C. Based on practice, up to 30% of dead nickel batteries can be revived in this way, and nickel-cadmium batteries can be “reanimated” much more readily. According to the charging time, electrical circuits of chargers can be divided into “accelerated” (charge current up to 0.7 C with a full charge time of 2 – 2.5 hours), “medium duration” (0.3 – 0.4 C – charge in 5 – 6 hours .) and “classic” (current 0.1C – charging time 12 – 15 hours). When designing a charger for a NiMH or NiCd battery, you can also use the generally accepted formula for calculating charging time in hours:
T = (E/I) ∙ 1.5
where E is the battery capacity, mA/h,
I – charge current, mA,
1.5 – coefficient for compensation of efficiency during charging.
For example, the charging time of a battery with a capacity of 1200 mAh. a current of 120 mA (0.1C) will be:
(1200/120)*1.5 = 15 hours.
From the experience of operating chargers for nickel batteries, it is worth noting that the lower the charging current, the more recharge cycles the element will endure. As a rule, the manufacturer indicates the passport cycles when charging the battery with a current of 0.1 C with the longest charge time. The charger can determine the degree of charge of the cans by measuring the internal resistance due to the difference in voltage drop at the time of charging and discharging with a certain current (∆U method).
So, taking into account all of the above, one of the simplest solutions for self-assembling the electrical circuit of the charger and at the same time highly efficient is Vitaly Sporysh’s circuit, a description of which can easily be found on the Internet.
The main advantages of this circuit are the ability to charge both one and two batteries connected in series, thermal control of the charge using a digital thermometer DS18B20, control and measurement of current during charging and discharging, automatic shutdown upon completion of charging, and the ability to charge the battery in an “accelerated” mode. In addition, with the help of specially written software and an additional board on the MAX232 TTL level converter chip, it is possible to control charging on a PC and further visualize it in the form of a graph. The disadvantages include the need for independent two-level power supply.
Lead-based (Pb) batteries can often be found in devices with high current consumption: cars, electric vehicles, uninterruptible power supplies, and as power sources for various power tools. There is no point in listing their advantages and disadvantages, which can be found on many sites on the Internet. In the process of implementing the electrical circuit of the charger for such batteries, two charging modes should be distinguished: buffer and cyclic.
Buffer charging mode involves simultaneously connecting both the charger and the load to the battery. This connection can be seen in uninterruptible power supplies, cars, wind and solar power systems. At the same time, during recharging, the device acts as a current limiter, and when the battery reaches its capacity, it switches to voltage limiting mode to compensate for self-discharge. In this mode, the battery acts as a supercapacitor. Cyclic mode involves turning off the charger when charging is complete and reconnecting it if the battery is low.
There are quite a lot of circuit solutions for charging these batteries on the Internet, so let’s look at some of them. For a novice radio amateur to implement a simple charger “on the knees,” the electrical circuit of the charger on the L200C chip from STMicroelectronics is perfect. The microcircuit is an ANALOG current regulator with the ability to stabilize voltage. Of all the advantages that this microcircuit has, it is the simplicity of the circuit design. Perhaps this is where all the advantages end. According to the datasheet for this chip, the maximum charge current can reach 2A, which theoretically will allow you to charge a battery with a capacity of up to 20 A/h with voltage 
(adjustable) from 8 to 18V. However, as it turned out in practice, this microcircuit has much more disadvantages than advantages. Already when charging a 12-amp lead-gel SLA battery with a current of 1.2A, the microcircuit requires a radiator with an area of at least 600 square meters. mm. A radiator with a fan from an old processor works well. According to the documentation for the microcircuit, voltages up to 40V can be applied to it. In fact, if you apply a voltage of more than 33V to the input. – the microcircuit burns out. This charger requires a fairly powerful power source capable of delivering a current of at least 2A. According to the above diagram, the secondary winding of the transformer should produce no more than 15 - 17V. alternating voltage. The output voltage value at which the charger determines that the battery has reached its capacity is determined by the Uref value on the 4th leg of the microcircuit and is set by the resistive divider R7 and R1. Resistors R2 – R6 create feedback, determining the limit value of the battery charging current. 
Resistor R2 at the same time determines its minimum value. When implementing a device, do not neglect the power value of the feedback resistances and it is better to use the ratings indicated in the circuit. To implement switching of the charging current, the best option would be to use a relay switch to which resistors R3 - R6 are connected. It is better to avoid using a low-resistance rheostat. This charger is capable of charging lead-based batteries with a capacity of up to 15 Ah. provided that the chip is well cooled.
The electrical circuit of a 3A pulse charger will help to significantly reduce the charging dimensions of small-capacity lead batteries (up to 20 A/h). current stabilizer with voltage regulation LM2576-ADJ.
For charging lead-acid or gel batteries with a capacity of up to 80A/h. (for example, automobiles). The impulse electrical circuit of a universal type charger presented below is perfect.
The circuit was successfully implemented by the author of this article in a case from an ATX computer power supply. Its elemental base is based on radioelements, mostly taken from a disassembled computer power supply. The charger works as a current stabilizer up to 8A. with adjustable charge cut-off voltage. Variable resistance R5 sets the value of the maximum charge current, and resistor R31 sets its limit voltage. A shunt on R33 is used as a current sensor. Relay K1 is necessary to protect the device from changing the polarity of the connection to the battery terminals. Pulse transformers T1 and T21 in finished form were also taken from a computer power supply. The electrical circuit of the charger works as follows:
1. turn on the charger with the battery disconnected (charging terminals folded back)
2. We set the charge voltage with variable resistance R31 (upper in the photo). For lead 12V. battery it should not exceed 13.8 - 14.0 V.
3. When the charging terminals are connected correctly, we hear the relay click, and on the lower indicator we see the value of the charging current, which we set with the lower variable resistance (R5 according to the diagram).
4. The charging algorithm is designed in such a way that the device charges the battery with a constant specified current. As the capacity accumulates, the charging current tends to a minimum value, and “recharging” occurs due to the previously set voltage.
A completely drained lead battery will not turn on the relay, nor will the charging itself. Therefore, it is important to provide a forced button for supplying instantaneous voltage from the internal power source of the charger to the control winding of relay K1. It should be remembered that when the button is pressed, the protection against polarity reversal will be disabled, so before a forced start, you need to pay special attention to the correct connection of the charger terminals to the battery. As an option, it is possible to start charging from a charged battery, and only then transfer the charging terminals to the required installed battery. The developer of the circuit can be found under the nickname Falconist on various radio-electronic forums.
To implement the voltage and current indicator, a circuit was used on the PIC16F690 pic controller and “super-available parts”, the firmware and operation description of which can be found on the Internet.
This electrical circuit of the charger, of course, does not claim to be a “reference”, but it is fully capable of replacing expensive industrial chargers, and can even significantly surpass many of them in functionality. In conclusion, it is worth saying that the latest universal charger circuit is designed mainly for a person trained in radio design. If you are just starting out, then it is better to use much simpler circuits in a powerful charger using an ordinary powerful transformer, a thyristor and its control system using several transistors. An example of the electrical circuit of such a charger is shown in the photo below.
See also diagrams.
