Kamaz

Do-it-yourself automatic drive for a car. How battery chargers work and how they work

Every motorist sooner or later has problems with the battery. I did not escape this fate either. After 10 minutes of unsuccessful attempts to start my car, I decided that I needed to purchase or make my own charger. In the evening, after checking out the garage and finding a suitable transformer there, I decided to do the charging myself.

There, among the unnecessary junk, I also found a voltage stabilizer from an old TV, which, in my opinion, would work wonderfully as a housing.

Having scoured the vast expanses of the Internet and really assessed my strengths, I probably chose the simplest scheme.

After printing out the diagram, I went to a neighbor who is interested in radio electronics. Within 15 minutes, he collected the necessary parts for me, cut off a piece of foil PCB and gave me a marker for drawing circuit boards. Having spent about an hour, I drew an acceptable board (the dimensions of the case allow for spacious installation). I won’t tell you how to etch the board, there is a lot of information about this. I took my creation to my neighbor, and he etched it for me. In principle, you could buy a circuit board and do everything on it, but as they say to a gift horse...
Having drilled all the necessary holes and displayed the pinout of the transistors on the monitor screen, I took up the soldering iron and after about an hour I had a finished board.

A diode bridge can be purchased on the market, the main thing is that it is designed for a current of at least 10 amperes. I found D 242 diodes, their characteristics are quite suitable, and I soldered a diode bridge on a piece of PCB.

The thyristor must be installed on a radiator, since it gets noticeably hot during operation.

Separately, I must say about the ammeter. I had to buy it in a store, where the sales consultant also picked up the shunt. I decided to modify the circuit a little and add a switch so that I could measure the voltage on the battery. Here, too, a shunt was needed, but when measuring voltage, it is connected not in parallel, but in series. The calculation formula can be found on the Internet; I would add that the dissipation power of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but my 4-watt shunt was heating up. The reason is unknown to me, I don’t have enough experience in such matters, but having decided that I mainly needed the readings of an ammeter, and not a voltmeter, I decided on it. Moreover, in voltmeter mode the shunt noticeably warmed up within 30-40 seconds. So, having collected everything I needed and checked everything on the stool, I took up the body. Having completely disassembled the stabilizer, I took out all its contents.

Having marked the front wall, I drilled holes for the variable resistor and switch, then using a small diameter drill around the circumference I drilled holes for the ammeter. Sharp edges were finished with a file.

After racking my brains a bit over the location of the transformer and radiator with thyristor, I settled on this option.

I bought a couple more crocodile clips and everything is ready to charge. The peculiarity of this circuit is that it only works under load, so after assembling the device and not finding voltage at the terminals with a voltmeter, do not rush to scold me. Just hang at least a car light bulb on the terminals, and you will be happy.

Take a transformer with a voltage on the secondary winding of 20-24 volts. Zener diode D 814. All other elements are indicated in the diagram.

I made this charger to charge car batteries, the output voltage is 14.5 volts, the maximum charge current is 6 A. But it can also charge other batteries, for example lithium-ion ones, since the output voltage and output current can be adjusted within a wide range. The main components of the charger were purchased on the AliExpress website.

These are the components:

You will also need an electrolytic capacitor 2200 uF at 50 V, a transformer for the TS-180-2 charger (see how to solder the TS-180-2 transformer), wires, a power plug, fuses, a radiator for the diode bridge, crocodiles. You can use another transformer with a power of at least 150 W (for a charging current of 6 A), the secondary winding must be designed for a current of 10 A and produce a voltage of 15 - 20 volts. The diode bridge can be assembled from individual diodes designed for a current of at least 10A, for example D242A.

The wires in the charger should be thick and short. The diode bridge must be mounted on a large radiator. It is necessary to increase the radiators of the DC-DC converter, or use a fan for cooling.

Charger assembly

Connect a cord with a power plug and a fuse to the primary winding of the TS-180-2 transformer, install the diode bridge on the radiator, connect the diode bridge and the secondary winding of the transformer. Solder the capacitor to the positive and negative terminals of the diode bridge.

Connect the transformer to a 220 volt network and measure the voltages with a multimeter. I got the following results:

The alternating voltage at the terminals of the secondary winding is 14.3 volts (mains voltage 228 volts).
The constant voltage after the diode bridge and capacitor is 18.4 volts (no load).

Using the diagram as a guide, connect a step-down converter and a voltammeter to the DC-DC diode bridge.

Setting the output voltage and charging current

There are two trimming resistors installed on the DC-DC converter board, one allows you to set the maximum output voltage, the other allows you to set the maximum charging current.

Plug in the charger (nothing is connected to the output wires), the indicator will show the voltage at the device output and the current is zero. Use the voltage potentiometer to set the output to 5 volts. Close the output wires together, use the current potentiometer to set the short circuit current to 6 A. Then eliminate the short circuit by disconnecting the output wires and use the voltage potentiometer to set the output to 14.5 volts.

This charger is not afraid of a short circuit at the output, but if the polarity is reversed, it may fail. To protect against polarity reversal, a powerful Schottky diode can be installed in the gap in the positive wire going to the battery. Such diodes have a low voltage drop when connected directly. With such protection, if the polarity is reversed when connecting the battery, no current will flow. True, this diode will need to be installed on a radiator, since a large current will flow through it during charging.

Suitable diode assemblies are used in computer power supplies. This assembly contains two Schottky diodes with a common cathode; they will need to be parallelized. For our charger, diodes with a current of at least 15 A are suitable.

It must be taken into account that in such assemblies the cathode is connected to the housing, so these diodes must be installed on the radiator through an insulating gasket.

It is necessary to adjust the upper voltage limit again, taking into account the voltage drop across the protection diodes. To do this, use the voltage potentiometer on the DC-DC converter board to set 14.5 volts measured with a multimeter directly at the output terminals of the charger.

How to charge the battery

Wipe the battery with a cloth soaked in soda solution, then dry. Remove the plugs and check the electrolyte level; if necessary, add distilled water. The plugs must be turned out during charging. No debris or dirt should get inside the battery. The room in which the battery is charged must be well ventilated.

Connect the battery to the charger and plug in the device. During charging, the voltage will gradually increase to 14.5 volts, the current will decrease over time. The battery can be conditionally considered charged when the charging current drops to 0.6 - 0.7 A.

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.

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

Every car owner needs a battery charger, but it costs a lot, and regular preventive trips to a car service center are not an option. Battery service at a service station takes time and money. In addition, with a discharged battery, you still need to drive to the service station. Anyone who knows how to use a soldering iron can assemble a working charger for a car battery with their own hands.

A little theory about batteries

Any battery is a storage device for electrical energy. When voltage is applied to it, energy is stored due to chemical changes inside the battery. When a consumer is connected, the opposite process occurs: a reverse chemical change creates voltage at the terminals of the device, and current flows through the load. Thus, in order to get voltage from the battery, you first need to “put it down,” that is, charge the battery.

Almost any car has its own generator, which, when the engine is running, provides power to the on-board equipment and charges the battery, replenishing the energy spent on starting the engine. But in some cases (frequent or difficult engine starts, short trips, etc.) the battery energy does not have time to be restored, and the battery is gradually discharged. There is only one way out of this situation - charging with an external charger.

How to find out the battery status

To decide whether charging is necessary, you need to determine the state of the battery. The simplest option - “turns/does not turn” - is at the same time unsuccessful. If the battery “doesn’t turn”, for example, in the garage in the morning, then you won’t go anywhere at all. The “does not turn” condition is critical, and the consequences for the battery can be dire.

The optimal and reliable method for checking the condition of a battery is to measure the voltage on it with a conventional tester. At an air temperature of about 20 degrees dependence of the degree of charge on voltage on the terminals of the battery disconnected from the load (!) is as follows:

12.6…12.7 V - fully charged;
12.3…12.4 V - 75%;
12.0…12.1 V - 50%;
11.8…11.9 V - 25%;
11.6…11.7 V - discharged;
below 11.6 V - deep discharge.

It should be noted that the voltage of 10.6 volts is critical. If it drops below, the “car battery” (especially a maintenance-free one) will fail.

Correct charging

There are two methods of charging a car battery - constant voltage and constant current. Everyone has their own features and disadvantages:

Homemade battery chargers

Assembling a charger for a car battery with your own hands is realistic and not particularly difficult. To do this, you need to have basic knowledge of electrical engineering and be able to hold a soldering iron in your hands.

Simple 6 and 12 V device

This scheme is the most basic and budget-friendly. Using this charger, you can efficiently charge any lead-acid battery with an operating voltage of 12 or 6 V and an electrical capacity of 10 to 120 A/h.

The device consists of a step-down transformer T1 and a powerful rectifier assembled using diodes VD2-VD5. The charging current is set by switches S2-S5, with the help of which quenching capacitors C1-C4 are connected to the power circuit of the primary winding of the transformer. Thanks to the multiple “weight” of each switch, various combinations allow you to stepwise adjust the charging current in the range of 1–15 A in 1 A increments. This is enough to select the optimal charging current.

For example, if a current of 5 A is required, then you will need to turn on the toggle switches S4 and S2. Closed S5, S3 and S2 will give a total of 11 A. To monitor the voltage on the battery, use a voltmeter PU1, the charging current is monitored using an ammeter PA1.

The design can use any power transformer with a power of about 300 W, including homemade ones. It should produce a voltage of 22–24 V on the secondary winding at a current of up to 10–15 A. In place of VD2-VD5, any rectifier diodes that can withstand a forward current of at least 10 A and a reverse voltage of at least 40 V are suitable. D214 or D242 are suitable. They should be installed through insulating gaskets on a radiator with a dissipation area of at least 300 cm2.

Capacitors C2-C5 must be non-polar paper with an operating voltage of at least 300 V. Suitable, for example, are MBChG, KBG-MN, MBGO, MBGP, MBM, MBGCh. Similar cube-shaped capacitors were widely used as phase-shifting capacitors for electric motors in household appliances. A DC voltmeter of type M5−2 with a measurement limit of 30 V was used as PU1. PA1 is an ammeter of the same type with a measurement limit of 30 A.

The circuit is simple, if you assemble it from serviceable parts, then it does not need adjustment. This device is also suitable for charging six-volt batteries, but the “weight” of each of the switches S2-S5 will be different. Therefore, you will have to navigate the charging currents using an ammeter.

With continuously adjustable current

Using this scheme, it is more difficult to assemble a charger for a car battery with your own hands, but it can be repeated and also does not contain scarce parts. With its help, it is possible to charge 12-volt batteries with a capacity of up to 120 A/h, the charge current is smoothly regulated.

The battery is charged using a pulsed current; a thyristor is used as a regulating element. In addition to the knob for smoothly adjusting the current, this design also has a mode switch, when turned on, the charging current doubles.

The charging mode is controlled visually using the RA1 dial gauge. Resistor R1 is homemade, made of nichrome or copper wire with a diameter of at least 0.8 mm. It serves as a current limiter. Lamp EL1 is an indicator lamp. In its place, any small-sized indicator lamp with a voltage of 24–36 V will do.

A step-down transformer can be used ready-made with an output voltage on the secondary winding of 18–24 V at a current of up to 15 A. If you don’t have a suitable device at hand, you can make it yourself from any network transformer with a power of 250–300 W. To do this, wind all windings from the transformer except the mains winding, and wind one secondary winding with any insulated wire with a cross-section of 6 mm. sq. The number of turns in the winding is 42.

Thyristor VD2 can be any of the KU202 series with the letters V-N. It is installed on a radiator with a dispersion area of at least 200 sq. cm. The power installation of the device is done with wires of minimal length and with a cross-section of at least 4 mm. sq. In place of VD1, any rectifier diode with a reverse voltage of at least 20 V and withstanding a current of at least 200 mA will work.

Setting up the device comes down to calibrating the RA1 ammeter. This can be done by connecting several 12-volt lamps with a total power of up to 250 W instead of a battery, monitoring the current using a known-good reference ammeter.

From a computer power supply

To assemble this simple charger with your own hands, you will need a regular power supply from an old ATX computer and knowledge of radio engineering. But the characteristics of the device will be decent. With its help, batteries are charged with a current of up to 10 A, adjusting the current and charge voltage. The only condition is that the power supply is desirable on the TL494 controller.

For creating DIY car charging from a computer power supply you will have to assemble the circuit shown in the figure.

Step by step steps required to finalize the operation will look like this:

Bite off all the power bus wires, with the exception of the yellow and black ones.
Connect the yellow and separately black wires together - these will be the “+” and “-” chargers, respectively (see diagram).
Cut all traces leading to pins 1, 14, 15 and 16 of the TL494 controller.
Install variable resistors with a nominal value of 10 and 4.4 kOhm on the power supply casing - these are the controls for regulating the voltage and charging current, respectively.
Using a suspended installation, assemble the circuit shown in the figure above.

If the installation is done correctly, then the modification is complete. All that remains is to equip the new charger with a voltmeter, an ammeter and wires with alligator clips for connecting to the battery.

In the design it is possible to use any variable and fixed resistors, except for the current resistor (the lower one in the circuit with a nominal value of 0.1 Ohm). Its power dissipation is at least 10 W. You can make such a resistor yourself from a nichrome or copper wire of the appropriate length, but you can actually find a ready-made one, for example, a 10 A shunt from a Chinese digital tester or a C5-16MV resistor. Another option is two 5WR2J resistors connected in parallel. Such resistors are found in switching power supplies for PCs or TVs.

What you need to know when charging a battery

When charging a car battery, it is important to follow a number of rules. This will help you Extend battery life and maintain your health:

The question of creating a simple battery charger with your own hands has been clarified. Everything is quite simple, all you have to do is stock up on the necessary tools and you can safely get to work.