Do-it-yourself charger for a car battery using a thyristor. How to make an automatic charger for a car battery with your own hands. Final assembly of the device

A thyristor battery charger has a number of advantages. This circuit allows you to safely charge any 12 V car battery, without the risk of boiling.

Additionally, devices of this type are suitable for restoring lead-acid batteries. This is achieved by monitoring charging parameters, which means the ability to simulate recovery modes.

A common, simple, but very effective thyristor phase-pulse power regulator circuit has long been used to charge lead-acid batteries.

Find out the charging time of your battery

Charging on KU202N allows:

• achieve charging current up to 10A;
• produce a pulse current that has a beneficial effect on the life expectancy of the battery;
• assemble the device yourself from inexpensive parts available at any radio electronics store;
• repeat the circuit diagram even for a beginner who is superficially familiar with the theory.

Conventionally, the presented scheme can be divided into:

• A step-down device is a transformer with two windings that converts 220V from the network into 18-22V, which is necessary for the operation of the device.
• The rectifier unit that converts the pulse voltage into a permanent one is assembled from 4 diodes or implemented using a diode bridge.
• Filters are electrolytic capacitors that cut off alternating components of the output current.
• Stabilization is carried out using zener diodes.
• The current regulator is produced by a component built on transistors, thyristors and variable resistance.
• Monitoring of output parameters is realized using an ammeter and a voltmeter.

Principle of operation

A circuit of transistors VT1 and VT2 controls the thyristor electrode. The current passes through VD2, which protects against return pulses. The optimal charging current is controlled by component R5. In our case, it should be equal to 10% of the battery capacity. To monitor the current regulator, this parameter must be installed in front of the connection terminals with an ammeter.

This circuit is powered by a transformer with an output voltage of 18 to 22 V. It is imperative to place the diode bridge, as well as the control thyristor, on the radiators to remove excess heat. The optimal radiator size should exceed 100cm2. When using diodes D242-D245, KD203, be sure to isolate them from the device body.

This thyristor charger circuit must be equipped with a fuse for the output voltage. Its parameters are selected according to your own needs. If you do not intend to use currents greater than 7 A, then a 7.3 A fuse will be sufficient.

Features of assembly and operation

Theristor testing circuit

Assembled according to the presented diagram Charger in the future it can be supplemented with automatic protective systems (against polarity reversal, short circuit, etc.). Particularly useful, in our case, will be the installation of a system for cutting off the current supply when charging the battery, which will protect it from overcharging and overheating.

It is advisable to complete other protective systems LED indicators, signaling short circuits and other problems.

Monitor the output current carefully as it may vary due to line fluctuations.

Like similar thyristor phase-pulse regulators, a charger assembled according to the presented circuit interferes with radio reception, so it is advisable to provide an LC filter for the network.

Thyristor KU202N can be replaced with similar ones KU202V, KU 202G or KU202E. You can also use the more productive T-160 or T-250.

DIY thyristor charger

To assemble the presented circuit yourself, you will need a minimum of time and effort, along with low costs for components. Most of the components can be easily replaced with analogues. Some parts can be borrowed from failed electrical equipment. Before use, the components should be checked, thanks to this, a charger assembled even from used parts will work immediately after assembly.

Unlike models on the market, the performance of a self-assembled charger is maintained over a larger range. You can charge a car battery from -350C to 350C. This and the ability to regulate the output current, giving the battery a large amperage, allows in a short time to compensate the battery for a charge sufficient to turn the starter on the engine.

Thyristor chargers have a place in car enthusiasts' garages due to their ability to safely charge a car battery. The schematic diagram of this device allows you to assemble it yourself using products from the radio market. If knowledge is not enough, you can use the services of radio amateurs who, for a fee that is several times less than the cost of a store-bought charger, will be able to assemble the device for you according to the diagram provided to them.

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:

1. 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.

1. 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.

1. 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.

1. 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.

1. 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:

1. A) Headlights not turned off when stopping and sub-zero temperatures are the most common causes of battery discharge on the road.
2. A) The battery fails if it is not recharged for a long time when the car is idle.
3. A) For recharging, a mains voltage of 220 V is used.
4. A) It is not advisable to charge the battery with a homemade device if it is not removed from the car.
5. 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: The car charger is designed to transfer electric current with a given voltage directly to Battery

Answers to 5 Frequently Asked Questions

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

1. 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.
2. You need to be very careful not to confuse “plus” and “minus”, otherwise Charger will burn.
3. 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:

1. Stack.
2. Sonar.
3. 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.

1. Direct to mains battery connection is prohibited. Chargers are intended for this purpose.
2. Even device made with high quality and 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:

1. dc-dc buck converter.
2. Ammeter.
3. Diode bridge KVRS 5010.
4. Hubs 2200 uF at 50 volts.
5. transformer TS 180-2.
6. Circuit breakers.
7. Plug for connecting to the network.
8. "Crocodiles" for connecting terminals.
9. 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 supplied pulse block power supply 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

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 being connected in series with the primary winding of the power transformer T1 ballast capacitors C4-C9. 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 switched on charger for at least 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.

Shown in the photo appearance 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 larger size scale 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 circuits alternating current.

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. Distinctive feature of this LED that it changes color when the connection polarity changes. 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 short 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 assembly experience electronic circuits or does not need to automatically turn off the charger after charging the battery, I propose a simplified version of the device circuit for charging 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 easily be 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.

Often car owners have to deal with the phenomenon of the inability to start the engine due to a low battery. To solve the problem, you will need to use a battery charger, which costs a lot of money. In order not to spend money on buying a new charger for a car battery, you can make it yourself. It is only important to find a transformer with the necessary characteristics. To make a homemade device, you don’t have to be an electrician, and the whole process will take no more than a few hours.

Features of battery operation

Not all drivers know that lead-acid batteries are used in cars. Such batteries are distinguished by their endurance, so they can last up to 5 years.

To charge lead-acid batteries, a current equal to 10% of the total battery capacity is used. This means that to charge a battery with a capacity of 55 A/h, a charging current of 5.5 A is required. If a very high current is applied, this can lead to boiling of the electrolyte, which, in turn, will lead to a decrease in service life devices. A small charging current does not extend the life of the battery, but it does not have a negative impact on the integrity of the device.

This is interesting! When a current of 25 A is supplied, the battery is quickly recharged, so within 5-10 minutes after connecting a charger with this rating, you can start the engine. Such a high current is produced by modern inverter chargers, but it negatively affects the battery life.

When charging the battery, the charging current flows back to the working one. The voltage for each can should not be higher than 2.7 V. A 12 V battery has 6 cans that are not connected to each other. Depending on the battery voltage, the number of cells differs, as well as the required voltage for each cell. If the voltage is higher, this will lead to a process of decomposition of the electrolyte and plates, which contributes to the failure of the battery. To prevent the electrolyte from boiling, the voltage is limited to 0.1 V.

The battery is considered discharged if, when connecting a voltmeter or multimeter, the devices show a voltage of 11.9-12.1 V. Such a battery should be recharged immediately. A charged battery has a voltage at the terminals of 12.5-12.7 V.

Example of voltage at the terminals of a charged battery

The charging process is the restoration of spent capacity. Charging batteries can be done in two ways:

1. D.C. In this case, the charging current is regulated, the value of which is 10% of the device capacity. Charging time is 10 hours. The charging voltage varies from 13.8 V to 12.8 V for the entire charging duration. The disadvantage of this method is that it is necessary to control the charging process and turn off the charger in time before the electrolyte boils. This method is gentle on the batteries and has a neutral effect on their service life. To implement this method, transformer chargers are used.
2. Constant pressure. In this case, a voltage of 14.4 V is supplied to the battery terminals, and the current varies from large values to smaller ones automatically. Moreover, this change in current depends on such a parameter as time. The longer the battery is charged, the lower the current becomes. The battery will not be able to be recharged unless you forget to turn off the device and leave it for several days. The advantage of this method is that after 5-7 hours the battery will be charged by 90-95%. The battery can also be left unattended, which is why this method is popular. However, few car owners know that this charging method is “emergency”. When using it, the service life of the battery is significantly reduced. In addition, the more often you charge in this way, the faster the device will discharge.

Now even an inexperienced driver can understand that if there is no need to rush into charging the battery, then it is better to give preference to the first option (in terms of current). With accelerated charge recovery, the service life of the device is reduced, so there is a high probability that you will need to buy a new battery in the near future. Based on the above, the material will consider options for manufacturing chargers based on current and voltage. For production, you can use any available devices, which we will discuss later.

Battery charging requirements

Before carrying out the procedure for making a homemade battery charger, you must pay attention to the following requirements:

1. Providing a stable voltage of 14.4 V.
2. Device autonomy. This means that a homemade device should not require supervision, since the battery is often charged at night.
3. Ensuring that the charger turns off when the charging current or voltage increases.
4. Reverse polarity protection. If the device is connected to the battery incorrectly, the protection should be triggered. For implementation, a fuse is included in the circuit.

Polarity reversal is a dangerous process, as a result of which the battery may explode or boil. If the battery is in good condition and only slightly discharged, then if the charger is connected incorrectly, the charging current will increase above the rated one. If the battery is discharged, then when the polarity is reversed, an increase in voltage above the set value is observed and, as a result, the electrolyte boils.

Options for homemade battery chargers

Before you start developing a battery charger, it is important to understand that such a device is homemade and can negatively affect the battery life. However, sometimes such devices are simply necessary, as they can significantly save money on purchasing factory-made devices. Let's look at what you can make your own battery chargers from and how to do it.

Charging from a light bulb and a semiconductor diode

This charging method is relevant in situations where you need to start a car on a dead battery at home. In order to do this, you will need the components to assemble the device and a 220 V alternating voltage source (socket). The circuit of a homemade charger for a car battery contains the following elements:

1. Incandescent lamp. An ordinary light bulb, which is also popularly referred to as “Ilyich’s lamp.” The power of the lamp affects the charging speed of the battery, so the higher this indicator, the faster you can start the engine. The best option is a lamp with a power of 100-150 W.
2. Semiconductor diode. An electronic element whose main purpose is to conduct current in only one direction. The need for this element in the charging design is to convert alternating voltage to direct voltage. Moreover, for such purposes you will need a powerful diode that can withstand a heavy load. You can use a diode, either domestic or imported. In order not to buy such a diode, it can be found in old receivers or power supplies.
3. Plug for connecting to a socket.
4. Wires with terminals (crocodiles) for connecting to the battery.

It is important! Before assembling such a circuit, you need to understand that there is always a risk to life, so you should be extremely careful and careful.

Connection diagram of a charger from a light bulb and a diode to a battery

The plug should be plugged into the socket only after the entire circuit has been assembled and the contacts have been insulated. To avoid the occurrence of short circuit current, a 10 A circuit breaker is included in the circuit. When assembling the circuit, it is important to take into account the polarity. The light bulb and semiconductor diode must be connected to the positive terminal circuit of the battery. When using a 100 W light bulb, a charging current of 0.17 A will flow to the battery. To charge a 2 A battery, you will need to charge it for 10 hours. The higher the power of the incandescent lamp, the higher the charging current.

It makes no sense to charge a completely dead battery with such a device, but recharging it in the absence of a factory charger is quite possible.

Battery charger from rectifier

This option also falls into the category of the simplest homemade chargers. The basis of such a charger includes two main elements - a voltage converter and a rectifier. There are three types of rectifiers that charge the device in the following ways:

• D.C;
• alternating current;
• asymmetrical current.

Rectifiers of the first option charge the battery exclusively with direct current, which is cleared of alternating voltage ripples. AC rectifiers apply pulsating AC voltage to the battery terminals. Asymmetric rectifiers have a positive component, and half-wave rectifiers are used as the main design elements. This scheme has better results compared to DC and AC rectifiers. It is its design that will be discussed further.

In order to assemble a high-quality battery charging device, you will need a rectifier and a current amplifier. The rectifier consists of the following elements:

• fuse;
• powerful diode;
• Zener diode 1N754A or D814A;
• switch;
• variable resistor.

Electrical circuit of an asymmetric rectifier

In order to assemble the circuit, you will need to use a fuse rated for a maximum current of 1 A. The transformer can be taken from an old TV, the power of which should not exceed 150 W, and the output voltage should be 21 V. As a resistor, you need to take a powerful element of the MLT- brand 2. The rectifier diode must be designed for a current of at least 5 A, so the best option is models like D305 or D243. The amplifier is based on a regulator based on two transistors of the KT825 and 818 series. During installation, the transistors are installed on radiators to improve cooling.

The assembly of such a circuit is carried out using a hinged method, that is, all the elements are located on the old board cleared of tracks and connected to each other using wires. Its advantage is the ability to adjust the output current for charging the battery. The disadvantage of the diagram is the need to find the necessary elements, as well as arrange them correctly.

The simplest analogue of the above diagram is a more simplified version, shown in the photo below.

Simplified circuit of a rectifier with a transformer

It is proposed to use a simplified circuit using a transformer and rectifier. In addition, you will need a 12 V and 40 W (car) light bulb. Assembling the circuit is not difficult even for a beginner, but it is important to pay attention to the fact that the rectifier diode and the light bulb must be located in the circuit that is fed to the negative terminal of the battery. The disadvantage of this scheme is that it produces a pulsating current. To smooth out pulsations, as well as reduce strong beats, it is recommended to use the circuit presented below.

A circuit with a diode bridge and a smoothing capacitor reduces ripple and reduces runout

Charger from a computer power supply: step-by-step instructions

IN Lately A popular option for car charging is that you can make it yourself using computer unit nutrition.

Initially you will need a working power supply. Even a unit with a power of 200 W is suitable for such purposes. It produces a voltage of 12 V. It will not be enough to charge the battery, so it is important to increase this value to 14.4 V. Step-by-step instruction Making a charger for a battery from a computer power supply looks like this:

1. Initially, all excess wires that come out of the power supply are soldered off. You only need to leave the green wire. Its end needs to be soldered to the negative contacts, where the black wires come from. This manipulation is done so that when the unit is connected to the network, the device starts up immediately.

   

   The end of the green wire must be soldered to the negative contacts where the black wires were located

2. The wires that will be connected to the battery terminals must be soldered to the minus and plus output contacts of the power supply. The plus is soldered to the exit point of the yellow wires, and the minus to the exit point of the black ones.
3. At the next stage, it is necessary to reconstruct the operating mode of pulse width modulation (PWM). The TL494 or TA7500 microcontroller is responsible for this. For reconstruction you will need the lower leftmost leg of the microcontroller. To get to it, you need to turn the board over.

   

   The TL494 microcontroller is responsible for the PWM operating mode

4. Three resistors are connected to the bottom pin of the microcontroller. We are interested in the resistor that is connected to the output of the 12 V block. It is marked in the photo below with a dot. This element should be unsoldered, and then measure the resistance value.

   

   The resistor indicated by the purple dot must be desoldered

5. The resistor has a resistance of about 40 kOhm. It must be replaced with a resistor with a different resistance value. To clarify the value of the required resistance, you must first solder a regulator (variable resistor) to the contacts of the remote resistor.

   

   A regulator is soldered in place of the removed resistor

6. Now you should connect the device to the network, having previously connected a multimeter to the output terminals. The output voltage is changed using a regulator. You need to get a voltage value of 14.4 V.

   

   Output voltage is regulated by variable resistor

7. As soon as the voltage value is reached, the variable resistor should be unsoldered, and then the resulting resistance should be measured. For the example described above, its value is 120.8 kOhm.

   

   The resulting resistance should be 120.8 kOhm

8. Based on the obtained resistance value, you should select a similar resistor, and then solder it in place of the old one. If you cannot find a resistor of this resistance value, then you can select it from two elements.

   

   Soldering resistors in series adds up their resistance

9. After this, the functionality of the device is checked. If desired, you can install a voltmeter (or an ammeter) to the power supply, which will allow you to monitor the voltage and charging current.

General view of the charger from the computer power supply

This is interesting! The assembled charger has the function of protection against short circuit current, as well as against overload, but it does not protect against polarity reversal, so you should solder the output wires of the appropriate color (red and black) so as not to mix them up.

When connecting the charger to the battery terminals, a current of about 5-6 A will be supplied, which is the optimal value for devices with a capacity of 55-60 A/h. The video below shows how to make a charger for a battery from a computer power supply with voltage and current regulators.

What other charger options are there for batteries?

Let's consider a few more options for independent battery chargers.

Using a laptop charger for the battery

One of the simplest and quick ways reviving a dead battery. To implement the scheme for reviving the battery using charging from a laptop, you will need:

1. Charger for any laptop. The charger parameters are 19 V and the current is about 5 A.
2. Halogen lamp with a power of 90 W.
3. Connecting wires with clamps.

Let's move on to the implementation of the scheme. The light bulb is used to limit the current to an optimal value. You can use a resistor instead of a light bulb.

A laptop charger can also be used to “revive” a car battery.

Assembling such a scheme is not difficult. If you do not plan to use the laptop charger for its intended purpose, you can cut off the plug and then connect the clamps to the wires. First, use a multimeter to determine the polarity. The light bulb is connected to a circuit that goes to the positive terminal of the battery. The negative terminal from the battery is connected directly. Only after connecting the device to the battery can voltage be supplied to the power supply.

DIY charger from a microwave oven or similar devices

Using the transformer block, which is located inside the microwave, you can make a charger for the battery.

Step-by-step instructions for making a homemade charger from a transformer block from a microwave are presented below.

Connection diagram of a transformer block, diode bridge and capacitor to a car battery

The device can be assembled on any base. It is important that all structural elements are reliably protected. If necessary, the circuit can be supplemented with a switch, as well as a voltmeter.

Transformerless charger

If the search for a transformer has led to a dead end, then you can use the simplest circuit without step-down devices. Below is a diagram that allows you to implement a charger for a battery without using voltage transformers.

Electrical circuit of the charger without using a voltage transformer

The role of transformers is performed by capacitors, which are designed for a voltage of 250V. The circuit should include at least 4 capacitors, placing them in parallel. A resistor and an LED are connected in parallel to the capacitors. The role of the resistor is to dampen the residual voltage after disconnecting the device from the network.

The circuit also includes a diode bridge designed to operate with currents up to 6A. The bridge is included in the circuit after the capacitors, and the wires going to the battery for charging are connected to its terminals.

How to charge a battery from a homemade device

Separately, you should understand the question of how to properly charge the battery with a homemade charger. To do this, it is recommended to adhere to the following recommendations:

1. Maintain polarity. It is better to once again check the polarity of a homemade device with a multimeter rather than “biting your elbows”, because the cause of battery failure was an error with the wires.
2. Do not test the battery by shorting the contacts. This method only “kills” the device, and does not revive it, as indicated in many sources.
3. The device should be connected to a 220 V network only after the output terminals are connected to the battery. The device is turned off in the same way.
4. Compliance with safety precautions, since work is carried out not only with electricity, but also with battery acid.
5. The battery charging process must be monitored. The slightest malfunction can cause serious consequences.

Based on the above recommendations, it should be concluded that homemade devices, although acceptable, are still not capable of replacing factory ones. Making your own charger is not safe, especially if you are not confident that you can do it correctly. The material presents the simplest schemes for implementing chargers for car batteries, which will always be useful in the household.

Compliance with the operating mode of rechargeable batteries, and in particular the charging mode, guarantees their trouble-free operation throughout their entire service life. Charging batteries produce a current, the value of which can be determined by the formula

where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.

A classic charger for a car battery consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats (see Fig. 1) and transistor current stabilizers are used as current regulators.

In both cases, these elements generate significant thermal power, which reduces the efficiency of the charger and increases the likelihood of its failure.

To regulate the charging current, you can use a store of capacitors connected in series with the primary (mains) winding of the transformer and acting as reactances that dampen excess network voltage. A simplified version of such a device is shown in Fig. 2.

In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is insignificant.

The disadvantage in Fig. 2 is the need to provide a voltage on the secondary winding of the transformer one and a half times greater than the rated load voltage (~ 18÷20V).

The charger circuit, which provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.

It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.

Switches Q1 - Q4 can be used to connect various combinations of capacitors and thereby regulate the charging current.

The variable resistor R4 sets the response threshold of K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.

In Fig. Figure 4 shows another charger in which the charging current is smoothly regulated from zero to the maximum value.

The change in current in the load is achieved by adjusting the opening angle of the thyristor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5. The maximum battery charging current is 10A, set with an ammeter. The device is provided on the mains and load side with fuses F1 and F2.

A version of the charger printed circuit board (see Fig. 4), 60x75 mm in size, is shown in the following figure:

In the diagram in Fig. 4, the secondary winding of the transformer must be designed for a current three times greater than the charging current, and accordingly, the power of the transformer must also be three times greater than the power consumed by the battery.

This circumstance is a significant drawback of chargers with a current regulator thyristor (thyristor).

Note:

The rectifier bridge diodes VD1-VD4 and the thyristor VS1 must be installed on radiators.

It is possible to significantly reduce power losses in the SCR, and therefore increase the efficiency of the charger, by moving the control element from the circuit of the secondary winding of the transformer to the circuit of the primary winding. such a device is shown in Fig. 5.

In the diagram in Fig. 5 control unit is similar to that used in the previous version of the device. SCR VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is approximately 10 times less than the charging current, relatively little thermal power is released on the diodes VD1-VD4 and the thyristor VS1 and they do not require installation on radiators. In addition, the use of an SCR in the primary winding circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the current curve shape coefficient (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing a design (for example, use a variable resistor with a plastic axis).

A version of the printed circuit board of the charger in Figure 5, measuring 60x75 mm, is shown in the figure below:

Note:

The rectifier bridge diodes VD5-VD8 must be installed on radiators.

In the charger in Figure 5 there is a diode bridge VD1-VD4 type KTs402 or KTs405 with the letters A, B, C. Zener diode VD3 type KS518, KS522, KS524, or made up of two identical zener diodes with a total stabilization voltage of 16÷24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is unijunction, type KT117A, B, V, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247, etc.). The diodes are installed on radiators with an area of ​​at least 200 sq.cm, and the radiators will become very hot; a fan can be installed in the charger case for ventilation.