DIY car battery charger. Do-it-yourself chargers for a car battery Schemes of simple chargers for car batteries using thyristors

I know that I’ve already gotten all sorts of different chargers, but I couldn’t help but repeat an improved copy of the thyristor charger for car batteries. Refinement of this circuit makes it possible to no longer monitor the state of charge of the battery, also provides protection against polarity reversal, and also saves the old parameters

On the left in the pink frame is a well-known circuit of a phase-pulse current regulator; you can read more about the advantages of this circuit

The right side of the diagram shows a car battery voltage limiter. The point of this modification is that when the voltage on the battery reaches 14.4V, the voltage from this part of the circuit blocks the supply of pulses to the left side of the circuit through transistor Q3 and charging is completed.

I laid out the circuit as I found it, and on the printed circuit board I slightly changed the values ​​of the divider with the trimmer

This is the printed circuit board I got in the SprintLayout project

The divider with trimmer on the board has changed, as mentioned above, and also added another resistor to switch voltages between 14.4V-15.2V. This voltage of 15.2V is necessary for charging calcium car batteries

There are three LED indicators on the board: Power, Battery connected, Polarity reversal. I recommend putting the first two green, the third LED red. The variable resistor of the current regulator is installed on the printed circuit board, the thyristor and diode bridge are placed on the radiator.

I'll post a couple of photos of the assembled boards, but not in the case yet. There are also no tests of a charger for car batteries yet. I'll post the rest of the photos once I'm in the garage.

I also started drawing the front panel in the same application, but while I’m waiting for a parcel from China, I haven’t started working on the panel yet

I also found on the Internet a table of battery voltages at different states of charge, maybe it will be useful to someone

An article about another simple charger would be interesting.

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Don’t want to delve into the routine of radio electronics? I recommend paying attention to the proposals of our Chinese friends. For a very reasonable price you can purchase quite high-quality chargers

A simple charger with an LED charging indicator, green battery is charging, red battery is charged.

There is short circuit protection and reverse polarity protection. Perfect for charging Moto batteries with a capacity of up to 20A/h; a 9A/h battery will charge in 7 hours, 20A/h in 16 hours. The price for this charger is only 403 rubles, free delivery

This type of charger is capable of automatically charging almost any type of 12V car and motorcycle batteries up to 80A/H. It has a unique charging method in three stages: 1. Constant current charging, 2. Constant voltage charging, 3. Drop charging up to 100%.
There are two indicators on the front panel, the first indicates the voltage and charging percentage, the second indicates the charging current.
Quite a high-quality device for home needs, the price is just RUR 781.96, free delivery. At the time of writing these lines number of orders 1392, grade 4.8 out of 5. When ordering, do not forget to indicate Eurofork

Charger for a wide variety of 12-24V battery types with current up to 10A and peak current 12A. Able to charge Helium batteries and SA\SA. The charging technology is the same as the previous one in three stages. The charger is capable of charging both automatically and manually. The panel has an LCD indicator indicating voltage, charging current and charging percentage.

A good device if you need to charge all possible types of batteries of any capacity, up to 150Ah

The described charger was developed for restoring and charging batteries of cars and motorcycles. Its main feature is a pulsed charging current, which has a positive effect on the time and quality of battery regeneration.
The new development uses a circuit based on composite thyristors, expands the control band, and does not require powerful cooling heat sinks. The circuit not only works out the optimal conditions for charging and restoring the battery, but also protects them when the nominal voltage level at the terminals is reached.
The voltage from the alternating network is supplied to the power transformer T1 through a network filter composed of capacitors C1, C2 and a network choke T2 with back-to-back windings. This filter suppresses the interference that occurs as a result of turning on the thyristors VS1 ... VS3. Network noise after the rectifier bridge VD1 is filtered by capacitor C5. The key thyristor control circuit includes a low-power thyristor VS1 with control circuits on a resistive divider R1-R2-R3 and an indication LED HL1. The lower arm of the divider is formed by resistor R2 and LED HL1, which performs two functions: an indicator of the presence of mains voltage and a control voltage stabilizer. Resistor R3 smoothly regulates the charge current.

Resistor R4 in the anode circuit of thyristor VS1 limits the control current of the key thyristor VS2 to the nominal level. The R5-HL2 chain is the load of VS1, and the glow of HL2 indicates the battery charge.
The control signal from the R3 engine (adjustable constant voltage level) is supplied to the control electrode of the thyristor VS1 and, at a certain voltage at its anode, opens VS1. A voltage appears on the R5-HL2 chain, which is supplied to the control electrode of the power thyristor VS2 and turns it on. The current from the rectifier bridge VD1 through the open thyristor VS2 passes through the measuring device PA1 to the charging battery GB1. Capacitors SZ and C4 reduce noise in the circuits, which eliminates random switching of the control thyristor VS1.

To protect the battery from overcharging, a limiting circuit is used. The switch on thyristor VS3 turns off the power thyristor VS2 when the voltage on the battery increases above a specified limit. When thyristor VS3 opens, the voltage at its anode drops to almost zero, as does the voltage at the control electrode of thyristor VS1, which closes. Power thyristor VS2 also closes and charging of battery GB1 stops. The HL2 LED goes out.
When the GB1 battery self-discharges for a long time, the voltage at its terminals decreases and the battery charge is resumed. Diode VD2 prevents the reverse supply of voltage from resistor R9 to the control electrode of thyristor VS1 in the charge current control circuit.
For normal operation of the protection, the voltage on the battery should not exceed 16.2... 16.8 volts. The protection response voltage is set using resistor R7. Initially, the resistor R7 slider is installed in the upper position according to the diagram. When the protection is triggered, the voltage on the battery is measured, then the engine slowly “lowers” ​​down and the charge switching voltage is monitored.
Main technical characteristics of the thyristor charger:
Mains voltage: 190-230 volts
Power: 200 watts
Maximum load current: 20 amperes
Average charge current: 3-5 amperes
Efficiency: more than 80%
Rated battery voltage: 12 volts
Battery capacity: 55-240 Ah
Charging time: 1-3 hours
All radio components of the device, both domestic and foreign:
FU1 - 2 amp fuse
T1 - network transformer for 16-18 volts and 20 amperes
T2-TLF214
VS1, VS3 - KU101B
VS2 - T122-25-6 - can be replaced with KU202N
VD1 - RS405L
VD2 - D106B - replace with D226B
VD3 - D818G - replace with KS168B
HL1 - AL307B - "Network"
HL2 - AL307V - "Charge"
R1 - 1.5 kOhm
R2, R5 - 2.2 kOhm
R3 - 47 kOhm
R4 - 120 Ohm
R6 - 1.3 kOhm
R7 - 10 kOhm
R8 - 33 kOhm
R9 - 510 Ohm
C1 - 0.33 uF x 275 volts
C2 - 0.1 uF x 450 volts
C3 - 0.1 µF
C4 - 2.2 uF x 16 volts
C5 - 0.33 µF
C6 - 1 uF x 16 volts

Charger for car batteries.

It’s not new to anyone if I say that any motorist should have a battery charger in their garage. Of course, you can buy it in a store, but when faced with this question, I came to the conclusion that I don’t want to buy an obviously not very good device at an affordable price. There are those in which the charging current is regulated by a powerful switch, which adds or reduces the number of turns in the secondary winding of the transformer, thereby increasing or decreasing the charging current, while in principle there is no current control device. This is probably the cheapest option for a factory-made charger, but a smart device is not that cheap, the price is really steep, so I decided to find a circuit on the Internet and assemble it myself. The selection criteria were as follows:

A simple scheme, without unnecessary bells and whistles;
- availability of radio components;
- smooth adjustment of charging current from 1 to 10 amperes;
- it is desirable that this is a diagram of a charging and training device;
- not complicated setup;
- stability of operation (according to reviews of those who have already done this scheme).

After searching the Internet, I came across an industrial circuit for a charger with regulating thyristors.

Everything is typical: a transformer, a bridge (VD8, VD9, VD13, VD14), a pulse generator with adjustable duty cycle (VT1, VT2), thyristors as switches (VD11, VD12), a charge control unit. Simplifying this design somewhat, we get a simpler diagram:

There is no charge control unit in this diagram, and the rest is almost the same: trans, bridge, generator, one thyristor, measuring heads and fuse. Please note that the circuit contains a KU202 thyristor; it is a little weak, so in order to prevent breakdown by high current pulses, it must be installed on a radiator. The transformer is 150 watt, or you can use a TS-180 from an old tube TV.

Adjustable charger with a charge current of 10A on the KU202 thyristor.

And one more device that does not contain scarce parts, with a charging current of up to 10 amperes. It is a simple thyristor power regulator with phase-pulse control.

The thyristor control unit is assembled on two transistors. The time during which capacitor C1 will charge before switching the transistor is set by variable resistor R7, which, in fact, sets the value of the battery charging current. Diode VD1 serves to protect the thyristor control circuit from reverse voltage. The thyristor, as in the previous schemes, is placed on a good radiator, or on a small one with a cooling fan. The printed circuit board of the control unit looks like this:

The scheme is not bad, but it has some disadvantages:
- fluctuations in supply voltage lead to fluctuations in the charging current;
- no short circuit protection other than a fuse;
- the device interferes with the network (can be treated with an LC filter).

Charging and restoring device for rechargeable batteries.

This pulse device can charge and restore almost any type of battery. The charging time depends on the condition of the battery and ranges from 4 to 6 hours. Due to the pulsed charging current, the battery plates are desulfated. See the diagram below.

In this scheme, the generator is assembled on a microcircuit, which ensures more stable operation. Instead of NE555 you can use the Russian analogue - timer 1006VI1. If anyone doesn’t like the KREN142 for powering the timer, it can be replaced with a conventional parametric stabilizer, i.e. resistor and zener diode with the required stabilization voltage, and reduce resistor R5 to 200 Ohm. Transistor VT1- on the radiator without fail, it gets very hot. The circuit uses a transformer with a 24 volt secondary winding. A diode bridge can be assembled from diodes like D242. For better cooling of the transistor heatsink VT1 You can use a fan from a computer power supply or system unit cooling.

Restoring and charging the battery.

As a result of improper use of car batteries, their plates can become sulfated and the battery fails.
There is a known method for restoring such batteries when charging them with an “asymmetrical” current. In this case, the ratio of charging and discharging current is selected to be 10:1 (optimal mode). This mode allows you not only to restore sulfated batteries, but also to carry out preventive treatment of serviceable ones.

Rice. 1. Electrical circuit of the charger

In Fig. 1 shows a simple charger designed to use the method described above. The circuit provides a pulse charging current of up to 10 A (used for accelerated charging). To restore and train batteries, it is better to set the pulse charging current to 5 A. In this case, the discharge current will be 0.5 A. The discharge current is determined by the value of resistor R4.
The circuit is designed in such a way that the battery is charged by current pulses during one half of the period of the mains voltage, when the voltage at the output of the circuit exceeds the voltage at the battery. During the second half-cycle, diodes VD1, VD2 are closed and the battery is discharged through load resistance R4.

The charging current value is set by regulator R2 using an ammeter. Considering that when charging the battery, part of the current also flows through resistor R4 (10%), the readings of ammeter PA1 should correspond to 1.8 A (for a pulse charging current of 5 A), since the ammeter shows the average value of the current over a period of time, and the charge produced during half the period.

The circuit provides protection for the battery from uncontrolled discharge in the event of an accidental loss of mains voltage. In this case, relay K1 with its contacts will open the battery connection circuit. Relay K1 is used of the RPU-0 type with an operating winding voltage of 24 V or a lower voltage, but in this case a limiting resistor is connected in series with the winding.

For the device, you can use a transformer with a power of at least 150 W with a voltage in the secondary winding of 22...25 V.
The PA1 measuring device is suitable with a scale of 0...5 A (0...3 A), for example M42100. Transistor VT1 is installed on a radiator with an area of ​​at least 200 square meters. cm, for which it is convenient to use the metal case of the charger design.

The circuit uses a transistor with a high gain (1000...18000), which can be replaced with a KT825 when changing the polarity of the diodes and zener diode, since it has a different conductivity (see Fig. 2). The last letter in the transistor designation can be anything.

Rice. 2. Electrical circuit of the charger

To protect the circuit from accidental short circuit, fuse FU2 is installed at the output.
The resistors used are R1 type C2-23, R2 - PPBE-15, R3 - C5-16MB, R4 - PEV-15, the value of R2 can be from 3.3 to 15 kOhm. Any VD3 zener diode is suitable, with a stabilization voltage from 7.5 to 12 V.
reverse voltage.

Which wire is better to use from the charger to the battery.

Of course, it is better to take flexible copper stranded, but the cross-section needs to be selected based on the maximum current that will flow through these wires, for this we look at the plate:

If you are interested in the circuitry of pulsed charge-recovery devices using the 1006VI1 timer in the master oscillator, read this article:

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 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 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 flows from it 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.

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

The charger assembled according to the presented diagram can later 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 equip other protective systems with LED indicators that indicate 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.