How to assemble a 24 volt charger. Charger for car battery

15.10.2023

When parked for a long time, the car battery discharges over time. On-board electrical equipment constantly consumes a small current, and the battery undergoes a self-discharge process. But even regular use of the machine does not always provide sufficient charge.

This is especially noticeable in winter on short trips. In such conditions, the generator does not have time to restore the charge spent on the starter. Only a car battery charger will help here. which you can do yourself.

Why do you need to charge the battery?

Modern cars use lead-acid batteries. Their peculiarity is that with a constant weak charge, plate sulfation process. As a result, the battery loses capacity and cannot cope with starting the engine. You can avoid this by regularly charging the battery from the network. With its help, you can recharge the battery and prevent, and in some cases even reverse, the sulfation process.

A homemade battery charger (UZ) is indispensable in cases where you leave the car in the garage for the winter. Due to self-discharge, the battery loses 15-30% capacity per month. Therefore, it will not be possible to start the car at the beginning of the season without first charging it.

Charger requirements for car batteries

Availability of automation. The battery is charged mainly at night. Therefore, the charger should not require control of current and voltage by the car owner.
Sufficient tension. The power supply (PS) must provide 14.5 V. If the voltage drops across the charger, you need to choose a higher voltage power supply.
Protective system. If the charging current is exceeded, the automation must irreversibly disconnect the battery. Otherwise, the device may fail and even catch fire. The system should be reset to its original state only after human intervention.
Reverse polarity protection. If the battery terminals are incorrectly connected to the charger, the circuit should immediately turn off. The system described above copes with this task.

Common mistakes in the design of homemade memory devices

Connecting the battery to the home electrical network through a diode bridge and ballast in the form of a capacitor with resistance. The large-capacity paper-oil capacitor required in this case will cost more than a purchased “charger”. This connection scheme creates a large reactive load, which can "to confuse" modern protection devices and electricity meters.
Creation of a charger based on a powerful transformer with a primary winding on 220V and secondary on 15V. There will be no problems with the operation of such equipment, and its reliability will be the envy of space technology. But making such a battery charger with your own hands will serve as a clear illustration of the expression "shoot sparrows from a cannon". And the heavy, bulky design is not ergonomic and easy to use.

Protection circuit

The probability that a short circuit will sooner or later occur at the output of the battery charger 100% . The cause may be a polarity reversal, a loose terminal, or another operator error. Therefore, you need to start with the design of the protection device (PD). It should respond quickly and clearly when overloaded and break the output circuit.

There are two designs of ultrasound:

External, designed as a separate module. They can be connected to any 14 volt DC source.
Internal, integrated into the body of a specific “charger”.

The classic Schottky diode circuit only helps if the battery is connected incorrectly. But the diodes will simply burn out from overload when connected to a discharged battery or a short circuit at the charger output

It is better to use the universal scheme presented in the figure. It uses relay hysteresis and the slow response of the acid battery to voltage surges.

When there is a load surge in the circuit, the voltage on the relay coil drops and it turns off, preventing overload. The problem is that this circuit does not protect against polarity reversal. Also, the system does not permanently shut down when the current is exceeded, rather than due to a short circuit. When overloaded, the contacts will begin to continuously “clap” and this process will not stop until they burn out. Therefore, another circuit based on a pair of transistors and a relay is considered better.

The relay winding here is connected by diodes in an “or” logical circuit to the self-locking circuit and control modules. Before operating the charger, you need to configure it by connecting a ballast load to it.

What current source to use

A DIY charger requires a power source. Parameters required for battery 14.5-15 V/ 2-5 A (amp hours). Switching power supplies (UPS) and transformer-based units have such characteristics.

The advantage of a UPS is that it may well already be available. But the labor intensity of creating a charger for a battery based on it is much higher. Therefore, it is not worth buying a switching power supply for use in a car charger. It is better then to make a simpler and cheaper power source from a transformer and a rectifier.

Battery charger diagram:

Power supply for “charging” from the UPS

The advantage of a power supply from a computer is that it already has a built-in protective circuit. However, you will have to work hard to redo the design a little. To do this you need to do the following:

remove all output wires except yellow ones (+12V), black (ground) and green (PC turn-on wire).
short-circuit the green and black wires;
install a power switch (if there is no standard one);
find the feedback resistor in the circuit +12V;
replace with a variable resistor 10 kOhm;
turn on the power supply;
by rotating the variable resistor, set it at the output 14.4 V;
measure the current resistance of the variable resistor;
replace the variable resistor with a constant one of the same value (2% tolerance);
connect a voltmeter to the output of the power supply to monitor the charging process (optional);
connect the yellow and black wires into two bundles;
connect wires with clamps to them for connection to the terminals.

Tip: You can use a universal multimeter instead of a voltmeter. To power it, you should leave one red wire (+5 V).

The DIY battery charger is ready. All that remains is to connect the device to the mains and charge the battery.

Charger on transformer

The advantage of a transformer power source is that its electrical inertia is higher than that of a battery. This improves the security and reliability of the circuit.

Unlike a UPS, there is no built-in protection. Therefore, you need to take care to prevent overloading the charger you made yourself. This is also extremely important for car batteries. Otherwise, with overcurrent and voltage overloads, any troubles are possible: from burnout of the windings to splashing of acid and even explosion of the battery.

Charger from an electronic transformer (Video)

This video talks about an adjustable power supply, which is based on a converted 12V electronic transformer with a power of 105 W. In combination with a pulse stabilizer module, a reliable and compact charger is obtained for all types of batteries. 1.4-26V 0-3A.

A homemade power supply consists of two blocks: a transformer and a rectifier.

You can find a ready-made part with suitable windings or wind it yourself. The second option is more preferable, since you can find a transformer with an output 14.3-14.5 volts you are unlikely to succeed. You will have to use ready-made solutions that provide 12.6 V. You can increase the voltage by about 0.6 V by assembling a rectifier with a midpoint using Schottky diodes.

The power of the windings must be at least 120 watt, diode parameters - 30 amp/ 35 volt. This is enough to charge the battery normally.

You can use a thyristor rectifier. To obtain 14 V at the output, the input AC voltage to the rectifier should be about 24 volts. It will not be difficult to find a transformer with such parameters.

The easiest way- buy an adjustable rectifier for 18 or 24 volts and adjust it so that it produces 14.4 V

You will need

Power transformer TS-180-2, wires with a cross-section of 2.5 mm2, four D242A diodes, power plug, soldering iron, solder, fuses 0.5A and 10A;
household light bulb with a power of up to 200 W;
a semiconductor diode that conducts electricity in only one direction. You can use a laptop charger as such a diode.

Instructions

A simple charger can be made from an old computer power supply. Since it requires a current of 10% of the battery's total capacity, any power supply with more than 150 volts of power can be an effective charging source. Almost all power supplies have a PWM controller based on a TL494 chip (or a similar KA7500). First of all, you need to unsolder the excess wires (from sources -5V, -12B, +5B, +12B). Then remove R1 and replace it with a trimming resistor with the highest value of 27 kOhm. The sixteenth terminal is also disconnected from the main wire, the fourteenth and fifteenth are cut at the connection point.

On the back plate of the block you need to install a potentiometer-current regulator R10. There are also 2 cords: one for the mains, the other for the battery terminals.

Now you need to deal with pins 1, 14,15 and 16. First, they need to be irradiated. To do this, the wire is cleared of insulation and burned with a soldering iron. This will remove the oxide film, after which the wire is applied to a piece of rosin, and then pressed again with a soldering iron. The wire should turn yellow-brown. Now you need to attach it to a piece of solder and press it with a soldering iron for the third and final time. The wire should turn silver. After completing this procedure, all that remains is to solder the stranded thin wires.

The idle speed must be set using a variable resistor with the potentiometer R10 in the middle position. The open circuit voltage will set the full charge to between 13.8 and 14.2 volts. Clips are installed at the ends of the terminals. It is better to make the insulating tubes multi-colored so as not to get tangled in the wires. This may damage the device. Red usually refers to "plus" and black to "minus".

If the device will only be used to charge the battery, you can do without a voltmeter and ammeter. It will be enough to use the graduated scale of the R10 potentiometer with a value of 5.5-6.5 amperes. The charging process from such a device should be easy, automatic and not require your additional efforts. This charger virtually eliminates the possibility of overheating or overcharging the battery.

Another method of manufacturing a car battery is based on the use of an adapted twelve-volt adapter. It does not require a car battery charger. It is important to remember that the battery voltage and power supply voltage must be equal, otherwise the charger will be useless.

First you need to cut and expose up to 5 cm the end of the adapter wire. Then the opposite wires are separated by 40 cm. Now you need to put an alligator clip on each of the wires. Don't forget to use different colored clips so you don't mix up the polarities. You need to connect each terminal to the battery in series, following the principle “from plus to plus” and “from minus to minus”. Now all that remains is to turn on the adapter. This method is quite simple, the only difficulty is choosing the right power source. This battery can overheat during charging, so it is important to monitor it and interrupt it for a while if it overheats.

A charger for a car battery can be made from an ordinary light bulb and a diode. Such a device will be very simple and requires very few initial elements: a light bulb, a semiconductor diode, wires with terminals and a plug. The light bulb must have a power of up to 200 volts. The higher its power, the faster the charging process will be. A semiconductor diode must conduct electricity in only one direction. You can take, for example, a laptop charger.

The light bulb should burn at half intensity, but if it doesn’t light up at all, you need to modify the circuit. It is possible that the light will turn off when the car battery is fully charged, but this is unlikely. Charging with such a device will take about 10 hours. Then you must disconnect it from the network, otherwise overheating is inevitable, which will damage the battery.

If the situation is urgent, and there is no time to build more complex chargers, you can charge the battery using a powerful diode and a heater using current from the mains. You need to connect to the network in the following sequence: diode, then heater, then battery. This method is ineffective because it consumes a lot of electricity, and the efficiency is only 1%. Therefore, this charger is the most unreliable, but also the easiest to manufacture.

Making the simplest charger will require considerable effort and technical knowledge. It is better to always have a reliable factory charger on hand, but if necessary and sufficient technical skills, you can make it yourself.

Every motorist has experienced a moment in life when, after turning the key in the ignition, absolutely nothing happened. The starter would not turn, and as a result, the car would not start. The diagnosis is simple and clear: the battery is completely discharged. But having even the simplest one with an output voltage of 12 V on hand, you can restore the battery within one hour and go about your business. How to make such a device with your own hands is described later in the article.

How to properly charge a battery

Before you make a battery charger with your own hands, you should learn the basic rules regarding how to properly charge it. If you do not follow them, the battery life will sharply decrease and you will have to buy a new one, since it is almost impossible to restore the battery.

To set the correct current, you need to know a simple formula: the charge current is equal to the battery discharge current over a period of time equal to 10 hours. This means that the battery capacity should be divided by 10. For example, for a battery with a capacity of 90 A/h, the charge current must be set to 9 Amperes. If you supply more, the electrolyte will heat up quickly and the lead honeycomb may be damaged. At a lower current, it will take a very long time to fully charge.

Now we need to deal with the tension. For batteries whose potential difference is 12 V, the charging voltage should not exceed 16.2 V. This means that for one bank the voltage should be within 2.7 V.

The most basic rule for proper battery charging: do not mix up the terminals when connecting the battery. Incorrectly connected terminals are called polarity reversal, which will lead to immediate boiling of the electrolyte and final failure of the battery.

Required tools and supplies

You can make a high-quality charger with your own hands only if you have prepared tools and consumables under your hands.

List of tools and consumables:

Multimeter. It should be in every motorist's tool bag. It will be useful not only when assembling the charger, but also in the future during repairs. A standard multimeter includes functions such as measuring voltage, current, resistance and continuity of conductors.
Soldering iron. A power of 40 or 60 W is sufficient. You cannot use a soldering iron that is too powerful, as high temperatures will lead to damage to dielectrics, for example, in capacitors.
Rosin. Necessary for a rapid increase in temperature. If the parts are not heated sufficiently, the soldering quality will be too low.
Tin. The main fastening material is used to improve the contact of two parts.
Heat-shrink tubing. A newer version of the old electrical tape, it is easy to use and has better dielectric properties.

Of course, tools such as pliers, a flat-head and shaped screwdriver should always be at hand. Having collected all the above elements, you can begin assembling the battery charger.

Sequence of manufacturing charging based on a switching power supply

Do-it-yourself battery charging should not only be reliable and of high quality, but also have a low cost. Therefore, the scheme below is ideal for achieving such goals.

Ready charging based on a switching power supply

What you will need:

Electronic type transformer from the Chinese manufacturer Tashibra.
Dinistor KN102. The foreign dinistor is marked DB3.
Power keys MJE13007 in the amount of two pieces.
Four KD213 diodes.
A resistor with a resistance of at least 10 Ohms and a power of 10 W. If you install a lower power resistor, it will constantly heat up and very soon fail.
Any feedback transformer that can be found in old radios.

You can place the circuit on any old board or buy a plate of inexpensive dielectric material for this. After assembling the circuit, it will need to be hidden in a metal case, which can be made from simple tin. The circuit must be isolated from the housing.

An example of a charger mounted in the case of an old system unit

The sequence of making a charger with your own hands:

Remake the power transformer. To do this, you need to unwind its secondary winding, since Tashibra pulse transformers provide only 12 V, which is very little for a car battery. In place of the old winding, 16 turns of a new double wire should be wound, the cross-section of which will not be less than 0.85 mm. The new winding is insulated, and the next one is wound on top of it. Only now you need to make only 3 turns, the wire cross-section is at least 0.7 mm.
Install short circuit protection. To do this you will need the same 10 ohm resistor. It should be soldered into the gap in the windings of the power transformer and the feedback transformer.

Resistor as short circuit protection

Using four KD213 diodes, solder the rectifier. The diode bridge is simple, can operate with high frequency current, and is manufactured according to a standard design.

Diode bridge based on KD213A

Making a PWM controller. Necessary in a charger, as it controls all power switches in the circuit. You can make it yourself using a field-effect transistor (for example, IRFZ44) and reverse conduction transistors. Elements of type KT3102 are ideal for these purposes.

PWM=high quality controller

Connect the main circuit with the power transformer and the PWM controller. After which the resulting assembly can be secured in a self-made housing.

This charger is quite simple, does not require large expenses for assembly, and is lightweight. But circuits made on the basis of pulse transformers cannot be classified as reliable. Even the simplest standard power transformer will produce more stable performance than pulsed devices.

When working with any charger, remember that polarity reversal must not be allowed. This charging is protected from this, but still, mixed-up terminals shorten the life of the battery, and a variable resistor in the circuit allows you to control the charging current.

Simple DIY charger

To make this charger, you will need elements that can be found in a used old-type TV. Before installing them in a new circuit, the parts must be checked with a multimeter.

The main part of the circuit is the power transformer, which cannot be found everywhere. Its marking: TS-180-2. A transformer of this type has 2 windings, the voltage of which is 6.4 and 4.7 V. To obtain the required potential difference, these windings should be connected in series - the output of the first should be connected to the input of the second by soldering or an ordinary terminal block.

Transformer type TS-180-2

You will also need four D242A type diodes. Since these elements will be assembled in a bridge circuit, excess heat will need to be removed from them during operation. Therefore, it is also necessary to find or purchase 4 cooling radiators for radio components with an area of at least 25 mm2.

All that remains is the base, for which you can take a fiberglass plate and 2 fuses, 0.5 and 10A. Conductors can be used of any cross-section, only the input cable must be at least 2.5 mm2.

Charger assembly sequence:

The first element in the circuit is to assemble a diode bridge. It is assembled according to the standard scheme. The terminal locations should be lowered down, and all diodes should be placed on cooling radiators.
From the transformer, from terminals 10 and 10′, draw 2 wires to the input of the diode bridge. Now you need to slightly modify the primary windings of the transformers, and to do this, solder a jumper between pins 1 and 1′.
Solder the input wires to pins 2 and 2′. The input wire can be made from any cable, for example, from any used household appliance. If only a wire is available, then you need to attach a plug to it.
A fuse rated at 0.5A should be installed in the gap in the wire leading to the transformer. In the positive gap, which will go directly to the battery terminal, there is a 10A fuse.
The negative wire coming from the diode bridge is soldered in series to an ordinary lamp rated at 12 V, with a power of no more than 60 W. This will help not only control battery charging, but also limit the charging current.

All elements of this charger can be placed in a tin case, also made by hand. Fix the fiberglass plate with bolts, and mount the transformer directly on the housing, having previously placed the same fiberglass plate between it and the sheet metal.

Ignoring the laws of electrical engineering can lead to the charger constantly failing. Therefore, it is worth planning the charging power in advance, depending on which to assemble the circuit. If you exceed the power of the circuit, then the battery will not be properly charged unless the operating voltage is exceeded.

The photo shows a homemade automatic charger for charging 12 V car batteries with a current of up to 8 A, assembled in a housing from a B3-38 millivoltmeter.

Why do you need to charge your car battery?
charger

The battery in the car is charged using an electric generator. To protect electrical equipment and devices from the increased voltage generated by a car generator, a relay-regulator is installed after it, which limits the voltage in the car’s on-board network to 14.1 ± 0.2 V. To fully charge the battery, a voltage of at least 14.5 is required IN.

Thus, it is impossible to fully charge the battery from a generator and before the onset of cold weather it is necessary to recharge the battery from a charger.

Analysis of charger circuits

The scheme for making a charger from a computer power supply looks attractive. The structural diagrams of computer power supplies are the same, but the electrical ones are different, and modification requires high radio engineering qualifications.

I was interested in the capacitor circuit of the charger, the efficiency is high, it does not generate heat, it provides a stable charging current regardless of the state of charge of the battery and fluctuations in the supply network, and is not afraid of output short circuits. But it also has a drawback. If during charging the contact with the battery is lost, the voltage on the capacitors increases several times (the capacitors and transformer form a resonant oscillatory circuit with the frequency of the mains), and they break through. It was necessary to eliminate only this one drawback, which I managed to do.

The result was a charger circuit without the above-mentioned disadvantages. For more than 16 years I have been charging any 12 V acid batteries with it. The device works flawlessly.

Schematic diagram of a car charger

Despite its apparent complexity, the circuit of a homemade charger is simple and consists of only a few complete functional units.

If the circuit to repeat seems complicated to you, then you can assemble a more one that works on the same principle, but without the automatic shutdown function when the battery is fully charged.

Current limiter circuit on ballast capacitors

In a capacitor car charger, regulation of the magnitude and stabilization of the battery charge current is ensured by connecting ballast capacitors C4-C9 in series with the primary winding of the power transformer T1. The larger the capacitor capacity, the greater the battery charging current.

In practice, this is a complete version of the charger; you can connect a battery after the diode bridge and charge it, but the reliability of such a circuit is low. If contact with the battery terminals is broken, the capacitors may fail.

The capacitance of the capacitors, which depends on the magnitude of the current and voltage on the secondary winding of the transformer, can be approximately determined by the formula, but it is easier to navigate using the data in the table.

To regulate the current in order to reduce the number of capacitors, they can be connected in parallel in groups. My switching is carried out using a two-bar switch, but you can install several toggle switches.

Protection circuit
from incorrect connection of battery poles

The protection circuit against polarity reversal of the charger in case of incorrect connection of the battery to the terminals is made using relay P3. If the battery is connected incorrectly, the VD13 diode does not pass current, the relay is de-energized, the K3.1 relay contacts are open and no current flows to the battery terminals. When connected correctly, the relay is activated, contacts K3.1 are closed, and the battery is connected to the charging circuit. This reverse polarity protection circuit can be used with any charger, both transistor and thyristor. It is enough to connect it to the break in the wires with which the battery is connected to the charger.

Circuit for measuring current and voltage of battery charging

Thanks to the presence of switch S3 in the diagram above, when charging the battery, it is possible to control not only the amount of charging current, but also the voltage. In the upper position of S3, the current is measured, in the lower position the voltage is measured. If the charger is not connected to the mains, the voltmeter will show the battery voltage, and when the battery is charging, the charging voltage. An M24 microammeter with an electromagnetic system is used as a head. R17 bypasses the head in current measurement mode, and R18 serves as a divider when measuring voltage.

Automatic charger shutdown circuit
when the battery is fully charged

To power the operational amplifier and create a reference voltage, a DA1 type 142EN8G 9V stabilizer chip is used. This microcircuit was not chosen by chance. When the temperature of the microcircuit body changes by 10º, the output voltage changes by no more than hundredths of a volt.

The system for automatically turning off charging when the voltage reaches 15.6 V is made on half of the A1.1 chip. Pin 4 of the microcircuit is connected to a voltage divider R7, R8 from which a reference voltage of 4.5 V is supplied to it. Pin 4 of the microcircuit is connected to another divider using resistors R4-R6, resistor R5 is a tuning resistor to set the operating threshold of the machine. The value of resistor R9 sets the threshold for switching on the charger to 12.54 V. Thanks to the use of diode VD7 and resistor R9, the necessary hysteresis is provided between the switch-on and switch-off voltages of the battery charge.

The scheme works as follows. When connecting a car battery to a charger, the voltage at the terminals of which is less than 16.5 V, a voltage sufficient to open transistor VT1 is established at pin 2 of microcircuit A1.1, the transistor opens and relay P1 is activated, connecting contacts K1.1 to the mains through a block of capacitors the primary winding of the transformer and battery charging begins.

As soon as the charge voltage reaches 16.5 V, the voltage at output A1.1 will decrease to a value insufficient to maintain transistor VT1 in the open state. The relay will turn off and contacts K1.1 will connect the transformer through the standby capacitor C4, at which the charge current will be equal to 0.5 A. The charger circuit will be in this state until the voltage on the battery decreases to 12.54 V. As soon as the voltage will be set equal to 12.54 V, the relay will turn on again and charging will proceed at the specified current. It is possible, if necessary, to disable the automatic control system using switch S2.

Thus, the system of automatic monitoring of battery charging will eliminate the possibility of overcharging the battery. The battery can be left connected to the included charger for at least a whole year. This mode is relevant for motorists who drive only in the summer. After the end of the racing season, you can connect the battery to the charger and turn it off only in the spring. Even if there is a power outage, when it returns, the charger will continue to charge the battery as normal.

The principle of operation of the circuit for automatically turning off the charger in case of excess voltage due to the lack of load collected on the second half of the operational amplifier A1.2 is the same. Only the threshold for completely disconnecting the charger from the supply network is set to 19 V. If the charging voltage is less than 19 V, the voltage at output 8 of the A1.2 chip is sufficient to hold the transistor VT2 in the open state, in which voltage is applied to the relay P2. As soon as the charging voltage exceeds 19 V, the transistor will close, the relay will release contacts K2.1 and the voltage supply to the charger will completely stop. As soon as the battery is connected, it will power the automation circuit, and the charger will immediately return to working condition.

Automatic charger design

All parts of the charger are placed in the housing of the V3-38 milliammeter, from which all its contents have been removed, except for the pointer device. The installation of elements, except for the automation circuit, is carried out using a hinged method.

The housing design of the milliammeter consists of two rectangular frames connected by four corners. There are holes made in the corners with equal spacing, to which it is convenient to attach parts.

The TN61-220 power transformer is secured with four M4 screws on an aluminum plate 2 mm thick, the plate, in turn, is attached with M3 screws to the lower corners of the case. The TN61-220 power transformer is secured with four M4 screws on an aluminum plate 2 mm thick, the plate, in turn, is attached with M3 screws to the lower corners of the case. C1 is also installed on this plate. The photo shows a view of the charger from below.

A 2 mm thick fiberglass plate is also attached to the upper corners of the case, and capacitors C4-C9 and relays P1 and P2 are screwed to it. A printed circuit board is also screwed to these corners, on which an automatic battery charging control circuit is soldered. In reality, the number of capacitors is not six, as in the diagram, but 14, since in order to obtain a capacitor of the required value it was necessary to connect them in parallel. The capacitors and relays are connected to the rest of the charger circuit via a connector (blue in the photo above), which made it easier to access other elements during installation.

A finned aluminum radiator is installed on the outer side of the rear wall to cool the power diodes VD2-VD5. There is also a 1 A Pr1 fuse and a plug (taken from the computer power supply) for supplying power.

The charger's power diodes are secured using two clamping bars to the radiator inside the case. For this purpose, a rectangular hole is made in the rear wall of the case. This technical solution allowed us to minimize the amount of heat generated inside the case and save space. The diode leads and supply wires are soldered onto a loose strip made of foil fiberglass.

The photo shows a view of a homemade charger on the right side. The installation of the electrical circuit is made with colored wires, alternating voltage - brown, positive - red, negative - blue wires. The cross-section of the wires coming from the secondary winding of the transformer to the terminals for connecting the battery must be at least 1 mm 2.

The ammeter shunt is a piece of high-resistance constantan wire about a centimeter long, the ends of which are sealed in copper strips. The length of the shunt wire is selected when calibrating the ammeter. I took the wire from the shunt of a burnt pointer tester. One end of the copper strips is soldered directly to the positive output terminal; a thick conductor coming from the contacts of relay P3 is soldered to the second strip. The yellow and red wires go to the pointer device from the shunt.

Printed circuit board of the charger automation unit

The circuit for automatic regulation and protection against incorrect connection of the battery to the charger is soldered on a printed circuit board made of foil fiberglass.

The photo shows the appearance of the assembled circuit. The printed circuit board design for the automatic control and protection circuit is simple, the holes are made with a pitch of 2.5 mm.

The photo above shows a view of the printed circuit board from the installation side with parts marked in red. This drawing is convenient when assembling a printed circuit board.

The printed circuit board drawing above will be useful when manufacturing it using laser printer technology.

And this drawing of a printed circuit board will be useful when applying current-carrying tracks of a printed circuit board manually.

The scale of the pointer instrument of the V3-38 millivoltmeter did not fit the required measurements, I had to draw my own version on the computer, print it on thick white paper and glue the moment on top of the standard scale with glue.

Thanks to the larger scale size and calibration of the device in the measurement area, the voltage reading accuracy was 0.2 V.

Wires for connecting the charger to the battery and network terminals

The wires for connecting the car battery to the charger are equipped with alligator clips on one side and split ends on the other side. The red wire is selected to connect the positive terminal of the battery, and the blue wire is selected to connect the negative terminal. The cross-section of the wires for connecting to the battery device must be at least 1 mm 2.

The charger is connected to the electrical network using a universal cord with a plug and socket, as is used to connect computers, office equipment and other electrical appliances.

About Charger Parts

Power transformer T1 is used type TN61-220, the secondary windings of which are connected in series, as shown in the diagram. Since the efficiency of the charger is at least 0.8 and the charging current usually does not exceed 6 A, any transformer with a power of 150 watts will do. The secondary winding of the transformer should provide a voltage of 18-20 V at a load current of up to 8 A. If there is no ready-made transformer, then you can take any suitable power and rewind the secondary winding. You can calculate the number of turns of the secondary winding of a transformer using a special calculator.

Capacitors C4-C9 type MBGCh for a voltage of at least 350 V. You can use capacitors of any type designed to operate in alternating current circuits.

Diodes VD2-VD5 are suitable for any type, rated for a current of 10 A. VD7, VD11 - any pulsed silicon ones. VD6, VD8, VD10, VD5, VD12 and VD13 are any that can withstand a current of 1 A. LED VD1 is any, VD9 I used type KIPD29. A distinctive feature of this LED is that it changes color when the connection polarity is changed. To switch it, contacts K1.2 of relay P1 are used. When charging with the main current, the LED lights up yellow, and when switching to the battery charging mode, it lights up green. Instead of a binary LED, you can install any two single-color LEDs by connecting them according to the diagram below.

The operational amplifier chosen is KR1005UD1, an analogue of the foreign AN6551. Such amplifiers were used in the sound and video unit of the VM-12 video recorder. The good thing about the amplifier is that it does not require bipolar power supply or correction circuits and remains operational at a supply voltage of 5 to 12 V. It can be replaced with almost any similar one. For example, LM358, LM258, LM158 are good for replacing microcircuits, but their pin numbering is different, and you will need to make changes to the printed circuit board design.

Relays P1 and P2 are any for a voltage of 9-12 V and contacts designed for a switching current of 1 A. P3 for a voltage of 9-12 V and a switching current of 10 A, for example RP-21-003. If there are several contact groups in the relay, then it is advisable to solder them in parallel.

Switch S1 of any type, designed to operate at a voltage of 250 V and having a sufficient number of switching contacts. If you don’t need a current regulation step of 1 A, then you can install several toggle switches and set the charging current, say, 5 A and 8 A. If you charge only car batteries, then this solution is completely justified. Switch S2 is used to disable the charge level control system. If the battery is charged with a high current, the system may operate before the battery is fully charged. In this case, you can turn off the system and continue charging manually.

Any electromagnetic head for a current and voltage meter is suitable, with a total deviation current of 100 μA, for example type M24. If there is no need to measure voltage, but only current, then you can install a ready-made ammeter designed for a maximum constant measuring current of 10 A, and monitor the voltage with an external dial tester or multimeter by connecting them to the battery contacts.

Setting up the automatic adjustment and protection unit of the automatic control unit

If the board is assembled correctly and all radio elements are in good working order, the circuit will work immediately. All that remains is to set the voltage threshold with resistor R5, upon reaching which the battery charging will be switched to low current charging mode.

The adjustment can be made directly while charging the battery. But still, it’s better to play it safe and check and configure the automatic control and protection circuit of the automatic control unit before installing it in the housing. To do this, you will need a DC power supply, which has the ability to regulate the output voltage in the range from 10 to 20 V, designed for an output current of 0.5-1 A. As for measuring instruments, you will need any voltmeter, pointer tester or multimeter designed to measure DC voltage, with a measurement limit from 0 to 20 V.

Checking the voltage stabilizer

After installing all the parts on the printed circuit board, you need to apply a supply voltage of 12-15 V from the power supply to the common wire (minus) and pin 17 of the DA1 chip (plus). By changing the voltage at the output of the power supply from 12 to 20 V, you need to use a voltmeter to make sure that the voltage at output 2 of the DA1 voltage stabilizer chip is 9 V. If the voltage is different or changes, then DA1 is faulty.

Microcircuits of the K142EN series and analogues have protection against short circuits at the output, and if you short-circuit its output to the common wire, the microcircuit will enter protection mode and will not fail. If the test shows that the voltage at the output of the microcircuit is 0, this does not always mean that it is faulty. It is quite possible that there is a short circuit between the tracks of the printed circuit board or one of the radio elements in the rest of the circuit is faulty. To check the microcircuit, it is enough to disconnect its pin 2 from the board and if 9 V appears on it, it means that the microcircuit is working, and it is necessary to find and eliminate the short circuit.

Checking the surge protection system

I decided to start describing the operating principle of the circuit with a simpler part of the circuit, which is not subject to strict operating voltage standards.

The function of disconnecting the charger from the mains in the event of a battery disconnection is performed by a part of the circuit assembled on an operational differential amplifier A1.2 (hereinafter referred to as the op-amp).

Operating principle of an operational differential amplifier

Without knowing the operating principle of the op-amp, it is difficult to understand the operation of the circuit, so I will give a brief description. The op-amp has two inputs and one output. One of the inputs, which is designated in the diagram by a “+” sign, is called non-inverting, and the second input, which is designated by a “–” sign or a circle, is called inverting. The word differential op-amp means that the voltage at the output of the amplifier depends on the difference in voltage at its inputs. In this circuit, the operational amplifier is switched on without feedback, in comparator mode – comparing input voltages.

Thus, if the voltage at one of the inputs remains unchanged, and at the second it changes, then at the moment of passing through the point of equality of voltages at the inputs, the voltage at the output of the amplifier will change abruptly.

Testing the Surge Protection Circuit

Let's return to the diagram. The non-inverting input of amplifier A1.2 (pin 6) is connected to a voltage divider assembled across resistors R13 and R14. This divider is connected to a stabilized voltage of 9 V and therefore the voltage at the point of connection of the resistors never changes and is 6.75 V. The second input of the op-amp (pin 7) is connected to the second voltage divider, assembled on resistors R11 and R12. This voltage divider is connected to the bus through which the charging current flows, and the voltage on it changes depending on the amount of current and the state of charge of the battery. Therefore, the voltage value at pin 7 will also change accordingly. The divider resistances are selected in such a way that when the battery charging voltage changes from 9 to 19 V, the voltage at pin 7 will be less than at pin 6 and the voltage at the op-amp output (pin 8) will be more than 0.8 V and close to the op-amp supply voltage. The transistor will be open, voltage will be supplied to the winding of relay P2 and it will close contacts K2.1. The output voltage will also close diode VD11 and resistor R15 will not participate in the operation of the circuit.

As soon as the charging voltage exceeds 19 V (this can only happen if the battery is disconnected from the output of the charger), the voltage at pin 7 will become greater than at pin 6. In this case, the voltage at the op-amp output will abruptly decrease to zero. The transistor will close, the relay will de-energize and contacts K2.1 will open. The supply voltage to the RAM will be interrupted. At the moment when the voltage at the output of the op-amp becomes zero, diode VD11 opens and, thus, R15 is connected in parallel to R14 of the divider. The voltage at pin 6 will instantly decrease, which will eliminate false positives when the voltages at the op-amp inputs are equal due to ripple and interference. By changing the value of R15, you can change the hysteresis of the comparator, that is, the voltage at which the circuit will return to its original state.

When the battery is connected to the RAM, the voltage at pin 6 will again be set to 6.75 V, and at pin 7 it will be less and the circuit will begin to operate normally.

To check the operation of the circuit, it is enough to change the voltage on the power supply from 12 to 20 V and connect a voltmeter instead of relay P2 to observe its readings. When the voltage is less than 19 V, the voltmeter should show a voltage of 17-18 V (part of the voltage will drop across the transistor), and if it is higher, zero. It is still advisable to connect the relay winding to the circuit, then not only the operation of the circuit will be checked, but also its functionality, and by the clicks of the relay it will be possible to control the operation of the automation without a voltmeter.

If the circuit does not work, then you need to check the voltages at inputs 6 and 7, the op-amp output. If the voltages differ from those indicated above, you need to check the resistor values of the corresponding dividers. If the divider resistors and diode VD11 are working, then, therefore, the op-amp is faulty.

To check the circuit R15, D11, it is enough to disconnect one of the terminals of these elements; the circuit will work, only without hysteresis, that is, it turns on and off at the same voltage supplied from the power supply. Transistor VT12 can be easily checked by disconnecting one of the R16 pins and monitoring the voltage at the output of the op-amp. If the voltage at the output of the op-amp changes correctly, and the relay is always on, it means that there is a breakdown between the collector and emitter of the transistor.

Checking the battery shutdown circuit when it is fully charged

The operating principle of op amp A1.1 is no different from the operation of A1.2, with the exception of the ability to change the voltage cutoff threshold using trimming resistor R5.

To check the operation of A1.1, the supply voltage supplied from the power supply smoothly increases and decreases within 12-18 V. When the voltage reaches 15.6 V, relay P1 should turn off and contacts K1.1 switch the charger to low current charging mode through a capacitor C4. When the voltage level drops below 12.54 V, the relay should turn on and switch the charger into charging mode with a current of a given value.

The switching threshold voltage of 12.54 V can be adjusted by changing the value of resistor R9, but this is not necessary.

Using switch S2, it is possible to disable the automatic operating mode by turning on relay P1 directly.

Capacitor charger circuit
without automatic shutdown

For those who do not have sufficient experience in assembling electronic circuits or do not need to automatically turn off the charger after charging the battery, I offer a simplified version of the circuit diagram for charging acid-acid car batteries. A distinctive feature of the circuit is its ease of repetition, reliability, high efficiency and stable charging current, protection against incorrect battery connection, and automatic continuation of charging in the event of a loss of supply voltage.

The principle of stabilizing the charging current remains unchanged and is ensured by connecting a block of capacitors C1-C6 in series with the network transformer. To protect against overvoltage on the input winding and capacitors, one of the pairs of normally open contacts of relay P1 is used.

When the battery is not connected, the contacts of relays P1 K1.1 and K1.2 are open and even if the charger is connected to the power supply, no current flows to the circuit. The same thing happens if you connect the battery incorrectly according to polarity. When the battery is connected correctly, the current from it flows through the VD8 diode to the winding of relay P1, the relay is activated and its contacts K1.1 and K1.2 are closed. Through closed contacts K1.1, the mains voltage is supplied to the charger, and through K1.2 the charging current is supplied to the battery.

At first glance, it seems that relay contacts K1.2 are not needed, but if they are not there, then if the battery is connected incorrectly, current will flow from the positive terminal of the battery through the negative terminal of the charger, then through the diode bridge and then directly to the negative terminal of the battery and diodes the charger bridge will fail.

The proposed simple circuit for charging batteries can 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.

Analysis of more than 11 circuits for making a charger with your own hands at home, new circuits for 2017 and 2018, how to assemble a circuit diagram in an hour.

TEST:

To understand whether you have the necessary information about batteries and chargers for them, you should take a short test:

What are the main reasons why a car battery discharges on the road?

A) The motorist got out of the vehicle and forgot to turn off the headlights.

B) The battery has become too hot due to exposure to sunlight.

Can the battery fail if the car is not used for a long time (sitting in a garage without starting)?

A) If left idle for a long time, the battery will fail.

B) No, the battery will not deteriorate, it will only need to be charged and it will function again.

What current source is used to recharge the battery?

A) There is only one option - a network with a voltage of 220 volts.

B) 180 Volt network.

Is it necessary to remove the battery when connecting a homemade device?

A) It is advisable to remove the battery from its installed location, otherwise there is a risk of damaging the electronics due to high voltage.

B) It is not necessary to remove the battery from its installed location.

If you confuse “minus” and “plus” when connecting a charger, will the battery fail?

A) Yes, if connected incorrectly, the equipment will burn out.

B) The charger simply will not turn on; you will need to move the necessary contacts to the correct places.

Answers:

A) Headlights not turned off when stopping and sub-zero temperatures are the most common causes of battery discharge on the road.
A) The battery fails if it is not recharged for a long time when the car is idle.
A) For recharging, a mains voltage of 220 V is used.
A) It is not advisable to charge the battery with a homemade device if it is not removed from the car.
A) The terminals should not be mixed up, otherwise the homemade device will burn out.

Battery on vehicles require periodic charging. The reasons for the discharge can be different - from headlights that the owner forgot to turn off, to negative temperatures outside in winter. For recharge battery You will need a good charger. This device is available in large varieties in auto parts stores. But if there is no opportunity or desire to purchase, then memory You can do it yourself at home. There are also a large number of schemes - it is advisable to study them all in order to choose the most suitable option.

Definition: A car charger is designed to transmit electric current with a given voltage directly to Battery

Answers to 5 Frequently Asked Questions

Will I need to take any additional measures before charging the battery in my car?– Yes, you will need to clean the terminals, since acid deposits appear on them during operation. Contacts It needs to be cleaned very well so that current flows to the battery without difficulty. Sometimes motorists use grease to treat terminals; this should also be removed.
How to wipe charger terminals?— You can buy a specialized product in a store or prepare it yourself. Water and soda are used as a self-made solution. The components are mixed and stirred. This is an excellent option for treating all surfaces. When the acid comes into contact with soda, a reaction will occur and the motorist will definitely notice it. This area will need to be thoroughly wiped to get rid of all acids. If the terminals were previously treated with grease, it can be removed with any clean rag.
If there are covers on the battery, do they need to be opened before charging?— If there are covers on the body, they must be removed.
Why is it necessary to unscrew the battery caps?— This is necessary so that the gases formed during the charging process can freely exit the case.
Is there a need to pay attention to the electrolyte level in the battery?- This is done without fail. If the level is lower than required, then you need to add distilled water inside the battery. Determining the level is not difficult - the plates must be completely covered with liquid.

It’s also important to know: 3 nuances about operation

The homemade product differs somewhat in its method of operation from the factory version. This is explained by the fact that the purchased unit has built-in functions, helping in work. They are difficult to install on a device assembled at home, and therefore you will have to adhere to several rules when operation.

A self-assembled charger will not turn off when the battery is fully charged. That is why it is necessary to periodically monitor the equipment and connect it to multimeter– for charge control.
You need to be very careful not to confuse “plus” and “minus”, otherwise Charger will burn.
The equipment must be turned off when connecting to charger.

By following these simple rules, you will be able to recharge correctly battery and avoid unpleasant consequences.

Top 3 charger manufacturers

If you don’t have the desire or ability to assemble it yourself memory, then pay attention to the following manufacturers:

Stack.
Sonar.
Hyundai.

How to avoid 2 mistakes when charging a battery

It is necessary to follow the basic rules in order to properly nourish battery by car.

Direct to mains battery connection is prohibited. Chargers are intended for this purpose.
Even device it is made with high quality and from good materials, you will still need to periodically monitor the process charging, so that troubles don't happen.

Following simple rules will ensure reliable operation of self-made equipment. It is much easier to monitor the unit than to spend money on components for repairs.

The simplest battery charger

Scheme of a 100% working 12 volt charger

Look at the picture for the diagram memory at 12 V. The equipment is intended for charging car batteries with a voltage of 14.5 Volts. The maximum current received during charging is 6 A. But the device is also suitable for other batteries - lithium-ion, since the voltage and output current can be adjusted. All the main components for assembling the device can be found on the Aliexpress website.

Required components:

dc-dc buck converter.
Ammeter.
Diode bridge KVRS 5010.
Hubs 2200 uF at 50 volts.
transformer TS 180-2.
Circuit breakers.
Plug for connecting to the network.
"Crocodiles" for connecting terminals.
Radiator for diode bridge.

Transformer any one can be used at your own discretion. The main thing is that its power is not lower than 150 W (with a charging current of 6 A). It is necessary to install thick and short wires on the equipment. The diode bridge is fixed on a large radiator.

Look at the picture of the charger circuit Dawn 2. It is compiled according to the original Memory If you master this scheme, you will be able to independently create a high-quality copy that is no different from the original sample. Structurally, the device is a separate unit, closed with a housing to protect the electronics from moisture and exposure to bad weather conditions. It is necessary to connect a transformer and thyristors on the radiators to the base of the case. You will need a board that will stabilize the current charge and control the thyristors and terminals.

1 smart memory circuit

Look at the picture for a circuit diagram of a smart charger. The device is necessary for connection to lead-acid batteries with a capacity of 45 amperes per hour or more. This type of device is connected not only to batteries that are used daily, but also to those on duty or in reserve. This is a fairly budget version of the equipment. It does not provide indicator, and you can buy the cheapest microcontroller.

If you have the necessary experience, then you can assemble the transformer yourself. There is also no need to install audible warning signals - if battery connects incorrectly, the discharge lamp will light up to indicate an error. The equipment must be equipped with a switching power supply of 12 volts - 10 amperes.

1 industrial memory circuit

Look at the industrial diagram charger from Bars 8A equipment. Transformers are used with one 16-volt power winding, several vd-7 and vd-8 diodes are added. This is necessary in order to provide a bridge rectifier circuit from one winding.

1 inverter device diagram

Look at the picture for a diagram of an inverter charger. This device discharges the battery to 10.5 Volts before charging. The current is used with a value of C/20: “C” indicates the capacity of the installed battery. After that process the voltage rises to 14.5 Volts using a discharge-charge cycle. The ratio of charge and discharge is ten to one.

1 electrical circuit charger electronics

1 powerful memory circuit

Look at the picture at the diagram of a powerful charger for a car battery. The device is used for acidic battery, having high capacity. The device easily charges a car battery with a capacity of 120 A. The output voltage of the device is self-regulated. It ranges from 0 to 24 volts. Scheme It is notable for the fact that it has few components installed, but it does not require additional settings during operation.

Many could already see the Soviet Charger. It looks like a small metal box and may seem quite unreliable. But this is not true at all. The main difference between the Soviet model and modern models is reliability. The equipment has structural capacity. In the event that to the old device connect the electronic controller, then charger it will be possible to revive. But if you no longer have one at hand, but there is a desire to assemble it, you need to study the diagram.

To the features their equipment includes a powerful transformer and rectifier, with the help of which it is possible to quickly charge even a very discharged battery. Many modern devices will not be able to reproduce this effect.