Automatic charger from a computer power supply. Charger for a car battery from a computer power supply

15.08.2023

To recharge the battery, the best option is a ready-made charger (charger). But you can do it yourself. There are many different ways to assemble a homemade memory device: from the simplest circuits using a transformer, to pulse circuits with the ability to adjust. The average in terms of complexity of execution is a memory from a computer power supply. The article describes how to make a charger from a computer power supply for a car battery with your own hands.

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Manufacturing instructions

Converting a computer PSU into a charger is not difficult, but you need to know the basic requirements for a charger designed to charge car batteries. For a car battery, the charger must have the following characteristics: the maximum voltage supplied to the battery must be 14.4 V, the maximum current depends on the charger itself. It is these conditions that are created in the electrical system of the car when recharging the battery from the generator (video by Rinat Pak).

Tools and materials

Considering the requirements described above, to make a memory device with your own hands, you first need to find a suitable power supply. Suitable used ATX in working order, the power of which is from 200 to 250 watts.

As a basis, we take a computer that has the following characteristics:

output voltage 12V;
rated voltage 110/220 V;
power 230 W;
the value of the maximum current is not more than 8 A.

Of the tools and materials you will need:

soldering iron and solder;
screwdriver;
2.7 kΩ resistor;
200 Ohm and 2 W resistor;
68 ohm and 0.5 W resistor;
resistor 0.47 ohm and 1 W;
resistor 1 kOhm and 0.5 W;
two capacitors for 25 V;
12 V automotive relay;
three diodes 1N4007 for 1 A;
silicone sealant;
green LED;
voltammeter;
"crocodiles";
flexible copper wires 1 meter long.

Having prepared all the necessary tools and spare parts, you can begin to manufacture a battery charger from a computer power supply.

Action algorithm

Charging the battery must be carried out under voltage in the range of 13.9-14.4 V. All computers work with a voltage of 12V. Therefore, the main task of the alteration is to raise the voltage coming from the PSU to 14.4 V.
The main alteration will be carried out with the PWM mode of operation. For this, the TL494 chip is used. You can use a PSU with absolute analogues of this circuit. This circuit is used to generate pulses, and also as a power transistor driver, which performs the function of protecting against high currents. To regulate the voltage at the output of the computer power supply, the TL431 chip is used, which is installed on an additional board.

There is also a tuning resistor, which makes it possible to adjust the output voltage in a narrow range.

Work on the alteration of the power supply consists of the following steps:

For alterations in the block, you first need to remove all unnecessary parts from it and solder the wires. In this case, the 220/110 V switch and the wires going to it are superfluous. The wires should be unsoldered from the PSU. The unit requires a voltage of 220 V to operate. By removing the switch, we will eliminate the possibility of the unit burning if the switch is accidentally switched to the 110 V position.
Next, solder, bite off unnecessary wires, or use any other method to remove them. First, we look for the blue 12V wire coming from the capacitor, we solder it. There can be two wires, both must be soldered. We only need a bundle of yellow wires with a 12 V output, leaving 4 pieces. We also need a mass - these are black wires, we also leave 4 of them. In addition, you need to leave one green wire. The remaining wires are completely removed or soldered.
On the board, along the yellow wire, we find two capacitors in a circuit with a voltage of 12V, they usually have a voltage of 16V, they must be replaced with 25V capacitors. Over time, capacitors become unusable, so even if the old parts are still in working condition, it is better to replace them.
At the next stage, we need to ensure the operation of the unit every time it is connected to the network. The fact is that the power supply unit in the computer works only if the corresponding wires in the output bundle are closed. In addition, overvoltage protection must be excluded. This protection is set in order to disconnect the power supply from the mains if the output voltage supplied to it exceeds a specified limit. It is necessary to exclude protection, since a voltage of 12 V is acceptable for a computer, and we need to get 14.4 V at the output. For built-in protection, this will be considered an overvoltage and it will turn off the unit.
The shutdown overvoltage action signal as well as the enable and disable signals pass through the same optocoupler. There are only three optocouplers on the board. With their help, communication is carried out between the low-voltage (output) and high-voltage (input) parts of the PSU. In order for the protection not to work in case of overvoltage, it is necessary to close the contacts of the corresponding optocoupler with a solder jumper. Thanks to this, the unit will always be in the on state if it is connected to the mains and will not depend on what voltage the output will be.
Then, in order to obtain a stable output voltage at idle, it is necessary to increase the load on the PSU output through the channel where the voltage was 12 V, and it will become 14.4 V, and through the 5 V channel, but we do not use it. A 200 ohm, 2 W resistor will be used as a load for the first 12 V channel, and a 68 ohm, 0.5 W resistor will be used to load the 5 V channel. Once these resistors are in place, the no-load output voltage at idle can be adjusted to 14.4V.
Next, you need to limit the current at the output. For each power supply it is individual. In our case, its value should not exceed 8 A. To achieve this, you need to increase the resistor value in the primary winding circuit of the power transformer, which is used as a sensor that serves to determine the overload. To increase the rating, the installed resistor must be replaced with a more powerful one with a resistance of 0.47 ohms and a power of 1 watt. After this replacement, the resistor will function as an overload sensor, so the output current will not exceed 10 A even if the output wires are shorted, simulating a short circuit.
At the last stage, you need to add a protection circuit for the power supply from connecting the charger to the battery with the wrong polarity. This is the circuit that will really be created with your own hands and is not in the computer's power supply. To assemble the circuit, you will need a 12 V automotive relay with 4 terminals and 2 diodes rated for a current of 1 A, for example, 1N4007 diodes. In addition, you need to connect the green LED. Thanks to the diode, it will be possible to determine the state of charge. If it glows, it means that the battery is connected correctly and is being charged. In addition to these details, you also need to take a resistor with a resistance of 1 kOhm and a power of 0.5 W. The figure shows the protection circuit.
The principle of operation of the scheme is as follows. The battery with the correct polarity is connected to the output of the charger, that is, the power supply. The relay is activated by the remaining energy in the battery. After the relay is activated, the battery starts charging from the assembled charger through the closed contact of the PSU relay. Charging will be confirmed by a glowing LED.
To prevent overvoltage that occurs during the disconnection of the coil due to the electromotive force of self-induction, a 1N4007 diode is connected in parallel with the relay circuit. It is better to glue the relay to the heatsink of the power supply with silicone sealant. Silicone retains its elasticity after drying and is resistant to thermal stresses such as contraction and expansion, heating and cooling. When the sealant dries, the remaining elements are attached to the relay contacts. Instead of sealant, bolts can be used as fasteners.
It is better to select wires for the charger in different colors, for example, red and black. They should have a cross section of 2.5 square meters. mm, be flexible, copper. The length must be at least a meter. At the ends of the wires, they must be equipped with alligator clips, special clips, with which the charger is connected to the battery terminals. To fix the wires in the case of the assembled device, you need to drill the appropriate holes in the radiator. Through them you need to pass two nylon ties, which will hold the wires.

Ready charger

To control the charging current, an ammeter can also be mounted in the charger case. It must be connected in parallel to the power supply circuit. As a result, we have a memory that we can use to charge the car battery and not only.

Conclusion

The advantage of this charger is that the battery will not be recharged when using the device and will not deteriorate, no matter how long it is connected to the charger.

The disadvantage of this charger is the absence of any indicators by which one could judge the degree of charge of the battery.

It is difficult to tell if the battery is charged or not. You can calculate the approximate charging time by using the readings on the ammeter and applying the formula: current strength in Amperes multiplied by time in hours. It was experimentally obtained that it takes 24 hours, that is, a day, to fully charge a conventional battery with a capacity of 55 A / h.

This charger retains the function of overload and short circuit. But if it is not protected from reverse polarity, you can not connect the charger to the battery with the wrong polarity, the device will fail.

The battery is one of the main components of the electrical network in any car. During operation, the battery charge may decrease, and a charger (charger) can be used to replenish it. Of course, for this purpose it is better to use a proprietary memory, but if you can’t buy such a device, then you can make a charger from a computer power supply for your own hands.

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Manufacturing instructions

A car battery charger can be made from a computer PSU. But keep in mind that the conversion of the power supply into a charger must be carried out in accordance with the clear instructions that you will find below. First of all, you need to remember that the maximum voltage value for charging the battery should be 14.4 volts. We will tell you more about how to build a charger from a computer power supply below.

A set of necessary tools and materials

To convert a computer block into a do-it-yourself charger, you first need a working PSU. Its power should be 200-250 W, the current strength should not exceed 8 amperes, and the output voltage should be 12 volts. Actually, almost every block has such characteristics.

As for additional elements, in order to get from a computer power supply, you will need:

a set of resistors with different resistance and voltage (from 0.47 Ohm to 2.7 kOhm, 0.5-2 volts);
two capacitor elements for 25 volts;
three diode components 1N4007 with a current of 1 ampere.

Also prepare a locksmith tool, including a soldering iron with rosin and tin, clamps for connection, copper wires, silicone sealant (the author of the video is the Rinat Pak channel).

Action algorithm

We always charge the battery with a voltage of 13.9 to 14.4 volts, since the charging of the block is only 12 volts, you will need to increase the voltage at its output. To do this, you will need to additionally install a converter, for example, the TL494 circuit.

So, how to make a computer power supply:

First you need to remove all unnecessary elements from the circuit and unsolder the wires, in particular, we are talking about the 220/110 volt switch, as well as the wires that are connected to it. We solder all the excess wiring, if necessary, uses wire cutters to remove unnecessary pieces. You need to solder the 12 volt blue wire that comes from the capacitor device - there can be two such wires, you need to solder both. The only thing you need to leave is a yellow wire harness with an output voltage of 12 volts, you also need a mass - these are four more cables, only black. Also leave the green postings, everything else needs to be deleted.
Using the same yellow cable, you need to find two capacitor elements, it is connected to them, they are also soldered, and a 25 volt component is put in their place.
Next, you need to remove the voltage protection, since a stationary PC requires 12 volts, and, as mentioned above, we need 14.4 volts.
Then inspect the board - it should have three optocouplers, each of which is used to transmit impulses from overvoltage protection. These optocouplers provide the interconnection between the low-voltage as well as the high-voltage components of the block. In order for the protection not to work in the event of surges, it will be necessary to close the contacts on the optocoupler, for this a jumper is used. When you close the contacts, the memory will always work when it is connected to the household network. The diagram below shows in more detail where to install the jumper.
After completing these steps, you will need to achieve an output voltage of 14.4 volts. To do this, you will need the TL431 board installed in the schematic. This component allows you to adjust the voltage on all tracks coming from the PSU. To increase this indicator, you will need a tuning resistor element, which is also located on the diagram. But this component makes it possible to increase the parameter only up to 13 volts.
Therefore, in order to provide the required performance, the second resistor connected in series with the trimmer must be changed. The device changes to an identical one, only the resistance of the second one should be lower and be 2.7 kOhm.
After that, it is necessary to solder the transistor element installed next to this circuit. In the photo below, this component is marked in red.
Further, a 200 Ohm resistor element is installed on the 12-volt channel, its power should be 2 W, and a 68 Ohm device is placed on the 5-volt channel, the power indicator of which is 0.5 W.
The next step will be to limit the value of the output current, this parameter is determined in accordance with the characteristics of the PSU. In order for the charger from the computer power supply to work properly, the current must be no more than 8 amperes. To do this, it will be necessary to increase the nominal value of the resistor, respectively, it should be changed to a powerful device with a resistance value of 0.47 ohms.
Then we proceed to the arrangement of the protection circuit, for this, take the usual 12-volt relay with two diode elements. In parallel, the relay should be connected to one diode, and the device itself must be fixed on the radiator, for this, use a sealant.
The final step will be to connect two wires with clamps, their cross section should be 2.5 square millimeters. These wires will connect to the battery outlets. Two holes should be drilled in the block body and cables should be pulled out; nylon ties can be used for better fixation. To provide current control, an ammeter can be added to the system, which is connected in parallel to the power supply circuit.

Photo gallery "Make a homemade memory"

Conclusion

The main advantage of the method described above is that the car battery will never be recharged and, accordingly, this will not affect its service life. It does not matter how long the battery will spend in the on state with the charger. Of the minuses, it should be noted that this charger does not imply the use of indicators that will allow you to determine the degree of charging and, accordingly, the need to turn off the device.

So in fact you won't know for sure if your battery is charged or not. But on average, as noted by our compatriots who have already used such a charger, the charge time is about a day. Remember that when connecting, you must always observe the polarity, if you confuse the plus with the minus, then the memory will simply burn out.

Video "Visual instructions for converting a PSU into a memory"

A more visual instruction for making a charger from a computer unit is shown in the video (the author is the Soldering Iron TV channel).

There is a lot of information on the Internet about converting ATX-AT computer power supplies into laboratory power supplies and chargers. I re-read more than a dozen articles about the alteration, but there is practically no information about self-assembly from the details of these same PC PSUs. Why is this so, because ATX is an excellent donor for a good power supply, and if it is assembled on some kind of left PWM, it can always be replaced with TL494, on a brand new neat board. And most importantly, your pay

My ATX 400W power supply burned out. I added him to five more brothers, I realized that I had to do something with them. I decided to start with the extreme 400W Bp, I was attracted to it by two 12V 12A and 15A buses, which in total gave 27A. But it turned out that both buses are connected to the same 12V output and it’s unlikely that the necessary Amperes will be collected there. But maybe I’ll squeeze out at least 20A, I thought and decided to assemble the power supply.

Assembly conditions:
- make AT from ATX
- universal board for further improvements
- minimum details
- PWM only TL494
- voltage stabilization 12V, 14.4V and current up to 20A

Having searched for AT power supply circuit diagrams in tyrnet, I chose the circuit and redid it a bit

Didn't do anything special to the block.
- Excluded extra strapping 5V 3.3V, etc.
- Reworked the divider circuits around the TL494 error comparators. Added the ability to: switch voltages 12.6V and 14.4V, smoothly adjust the load current
- Well, in general, I transferred ATX to 3528, to AT on TL494. One thing did not give rest, at what frequency the donor worked. But then it turned out that the frequency calculation formula for 3528 is the same as for TL494 F=1.1/RC. According to the scheme, the frequency is 73 kHz

Started making payments. After hours of torment, such a payment turned out.

The board is currently final and has never been assembled. The first version of the board is slightly lighter, there are no circuits around the error amplifiers, but the control is carried out from another board through an optocoupler transistor from 14 Vref to 4 leg DT. The second version excludes the optocoupler and control is carried out through dividers on an additional board, through the legs TL494 1,2,3,15,16. The first and second versions of the power supply board are working and one hundred percent tested. Therefore, be careful, check the new version of the board before manufacturing. If there are errors, write through the form, I will correct everything.

And a few words about the launch. passed according to tradition through an incandescent light bulb, everything worked. The output without stabilization turned out to be 19V. The next start was through a fuse, 24.2V appeared at the output. I connected 4.2A 24V lamps from the car to the load. Voltage dipped by 0.2V

When the stabilization of 14.4V was connected to the load, it gave 8.4A, the voltage dipped by 0.2V. Unfortunately I didn't take a photo.
It also reacts normally to current limiting. More than 10A has not yet loaded, Nothing. No photo yet

Well, a couple more photos of the assembled board before the first tests

Video of the assembled power supply-charger from ATX

That's all for now. More photos and updates as time goes by
With uv. Admin check

A rechargeable battery is a device that wears out and discharges during operation. To charge the battery, a special device is used, which you can buy or make yourself. We will talk about how to build a charger for a car battery from a computer and laptop power supply below.

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How to charge a battery from a computer power supply?

The cost of quality chargers is high. Therefore, many car owners decide to convert the ATX power supply from a stationary PC into a memory. This procedure is not particularly complicated, but before proceeding with the task and converting the power supply to charging, which can charge the machine battery, you should understand the requirements for the memory. In particular, the maximum voltage level supplied to the battery should be no more than 14.4 volts in order to prevent rapid battery wear.

The user Vetal in his video showed how you can convert the PSU into a charger.

Getting ready for the task

To build a homemade charger from a computer PSU for 200W, 300W or 350W (PWM 3528), you will need the following materials and tools:

clips ("crocodiles") for connection to the battery;
resistor element for 2.7 kOhm, as well as for 1 kOhm and 0.5 W;
soldering iron with tin and rosin;
two screwdrivers (cross and flat tip);
resistor elements for 200 ohms and 2 W, as well as for 68 ohms and 0.5 W;
conventional machine relay for 12V;
two capacitor elements for 25V;
three diodes 1N4007 for 1 ampere;
LED element (any color, but green is better);
silicone sealant;
voltammeter;
two flexible copper wires (1 meter each).

You will also need the power supply itself, which should have the following characteristics:

output voltage value - 12 volts;
rated voltage parameter - 110/220 V;
power value - 230 W;
the maximum current parameter is not higher than 8 amperes.

Step-by-step instruction

The procedure for charging a machine battery is carried out under voltage, the value of which is from 13.9 to 14.4 volts. All stationary units operate with a voltage of 220 V, so the primary task is to reduce the operating parameter to 14.4 V. The charging device is based on the TL494 (7500) chip, in its absence, you can use an analogue. The microcircuit is needed to generate signals and is used as a driver for a transistor element designed to protect the device from high current. There is another circuit on the additional power supply board - TL431 or another similar one, designed to adjust the output voltage parameter. There is also a resistor element for tuning, with which you can adjust the output voltage in a narrow range.

Learn more about how to convert a computer PSU into a battery charger for a car battery, learn from the video published by the Soldering TV channel.

To make your own conversion of a PSU from a computer into a charger for a car, read the diagram and follow the instructions:

To begin with, all unnecessary components and elements must be dismantled from the ATX computer PSU, after which the cables are soldered from it. Use a soldering iron to avoid damaging the contacts. It is necessary to remove the 220/110 volt switch with cables connected to it. By removing the switch, you can prevent the PSU from burning out if you accidentally switch it to 110V.
Then, unnecessary cables are unsoldered and removed from the device. Remove the blue wire connected to the capacitor element, use a soldering iron. In some PSUs, two wires are connected to the capacitor, both should be removed. Also on the board you will see a bundle of yellow cables with a 12 volt output, there should be four of them, leave them all. There should also be four black wires, they must also be left, since this is ground or ground. It is necessary to leave one more green posting, all the rest are removed.
Pay attention to the diagram. On the yellow wire, you can find two capacitor elements in a 12 volt electrical circuit. Their operating voltage is 16V, so immediately remove them by soldering and install two 25V capacitors. The capacitor elements swell and become inoperable. Even if they are intact and seemingly working, we recommend changing them.
Now we need to complete the task so that the power supply is automatically activated every time it is connected to the household network. The bottom line is that when the PSU is installed in a computer, its activation is carried out in the event of the closure of certain contacts at the output. It is necessary to remove the protection against power surges. This element is designed to automatically disconnect the computer's power supply from the household network in case of overvoltage. You need to remove it, because the PC requires 12 volts for optimal operation, and 14.4 V is needed for the charger to function. The protection installed in the unit will perceive 14.4 volts as a power surge, as a result of which the charger will turn off and will not be able to charge the battery car.
Two pulses pass to the optocoupler on the board - actions from protection against power surges, shutdown, as well as activation and deactivation. In total, there are three optocouplers in the circuit. Thanks to these elements, the connection between the input and output components of the block is carried out. These parts are called high voltage and low voltage. In order for the protection not to work during power surges, you should close the contacts of the optocoupler, this can be done using a jumper made of solder. This action will ensure the uninterrupted operation of the PSU when it is included in the household network.
Now we need to ensure that the value of the outgoing voltage is 14.4 volts. To complete the task, you will need the TL431 board installed on the additional circuit. Thanks to this component, the voltage is adjusted on all channels coming from the device. To increase the operating parameter, you will need a tuning resistor element located on the same circuit. With it, you can increase the voltage to 13 volts, but this is not enough for optimal operation of the charger. Therefore, a resistor connected in series with the trimmer must be replaced. It should be unsoldered, and a similar part should be installed instead, the resistance of which should be below 2.7 kOhm. This will increase the adjustment range of the output parameter and get the required 14.4 volts.
Remove the transistor element installed next to the TL431 board. This detail can adversely affect the functionality of the circuit. The transistor will prevent the device from maintaining the desired output voltage. In the photo below you will see the element, it is marked in red.
In order for the battery charging device to have a stable output voltage, it is necessary to increase the operating load parameter through the channel where the voltage of 12 volts passed. There is an additional channel for 5 volts, but it is not necessary to use it. To provide the load, a resistor component is required, the working resistance value of which will be 200 ohms, and the power will be 2 watts. A 68 ohm part is installed on the additional channel, the power value of which is 0.5 watts. When the resistor elements are soldered, you can adjust the output voltage to 14.4 volts without the need for a load.
Then the output current should be limited. This parameter is individual for any power supply. Our current strength should be no more than 8 amperes. To ensure this, it will be necessary to increase the value of the resistor component installed in the primary circuit of the winding, next to the transformer device. The latter is used as a sensor designed to determine the overload value. To increase the nominal value, the resistor must be replaced, a component with a resistance of 0.47 Ohm is mounted instead, and the power value will be 1 W. The resistor is carefully soldered, a new one is soldered in its place. After completing this task, the part will be used as a sensor, so the output current will be no more than 10 amps, even if a short circuit occurs.
To protect the machine battery from reverse polarity, when connecting a home-made charger, an additional circuit is installed in the device. This is a board that you have to make yourself, since it is not in the block itself. To develop it, you will need a prepared 12 volt relay, which should have four terminals. You will also need diode components, the current strength of which will be 1 ampere. Alternatively, parts 1N4007 can be used. The circuit should be supplemented with an LED that will indicate the state of the charging process. If the light is on, the car battery is connected to the charger correctly. In addition to these components, you will need a resistor element, the operating resistance of which will be 1 kOhm, and the power will be 0.5 W. The principle of operation of the scheme is as follows. The battery is connected via cables to the output of a homemade charger. The relay is activated due to the energy that remains from the battery. After the element is triggered, the charging process from the charger begins, as evidenced by the activation of the diode light bulb.
When the coil is deactivated, a voltage jump occurs as a result of the influence of the electromotive force of self-induction. To prevent its negative impact on the operation of the charger, two diode components must be added to the board in parallel. The relay is fixed on the PSU radiator device with a sealant. Thanks to this material, elasticity can be ensured, as well as the immunity of parts to thermal stress. We are talking about contraction and expansion, heating and cooling. When the glue dries, the remaining components must be connected to the relay contacts. If there is no sealant, ordinary bolts are suitable for fixing.
At the last stage, wires with "crocodiles" are connected to the block. It is better to use cables of different colors, for example, black and red or red and blue. This will prevent the polarity from being reversed. The length of the wire will be at least one meter, and their cross section should be 2.5 mm2. Clamps are connected to the ends of the cables, designed to be fixed on the battery terminals. To fix the wires on the body of a homemade charger, two holes of the corresponding diameter are drilled in the radiator device. Two nylon ties are threaded through the resulting holes, with which the cables will be fixed. An ammeter can be mounted in the charger, it will allow you to control the amount of current. The device is connected in parallel to the power supply circuit.
It remains to test the performance of the self-assembled memory.

1. Red marked jumper on the diagram 2. Transistor element on the board to be removed 3. Resistor element in the primary circuit to be replaced 4. Scheme for assembling a board designed to protect the PSU in case of polarity reversal

Charger from laptop power supply

You can build a charger from a laptop power supply.

You cannot directly connect the PSU to the battery terminals.

The output voltage varies around 19 volts, and the current strength is about 6 amperes. These parameters are sufficient to ensure that the battery is charged, but the voltage is too high. There are two ways to solve the problem.

No PSU modification

It will be necessary to connect the so-called ballast in the form of a powerful lamp from optics in a consistent manner with the car battery. The light source will be used as a current limiter. A simple and affordable option. One contact of the lamp is connected to the positive output of the laptop power supply, and its second contact is connected to the positive of the battery. The minus from the power supply is connected directly to the negative terminal of the battery via a wire. After that, the PSU can be connected to the household network. The method is very simple, but there is a possibility of failure of the light source. This will result in the inoperability of both the battery and the unit.

With alteration of the power supply

You will need to lower the PSU voltage parameter so that the output voltage is about 14-14.5 V.

Consider the process of manufacturing and assembling a charger using the example of a power supply from a Great Wall laptop:

First you need to disassemble the power supply housing. When disassembling, do not damage it, as it will be used for further operation. The board, which is located inside, can be connected to a voltmeter to find out exactly what its operating voltage is. In our case, it is 19.2 volts. A board built on TEA1751 + TEA1761 chips is used.
The task of reducing the voltage value is being performed. To do this, you need to find a resistor element located at the output. You need a part that connects the sixth pin of the TEA1761 circuit to the positive terminal of the power supply. This resistor element should be unsoldered with a soldering iron and its resistance measured. The operating parameter is 18 kOhm.
Instead of the dismantled element, a tuning resistor component of 22 kOhm is installed, but before soldering it should be set to 18 kOhm. Solder the part carefully so as not to damage other circuit elements.
Gradually lowering the resistance value, it is necessary to ensure that the output voltage parameter is 14-14.5 volts.
When you get the voltage that is optimal for charging a car battery, the soldered resistor can be soldered off. Its resistance parameter is measured, in our case it is 12.37 kOhm. According to this value or close to it, a constant resistor is selected. We use two resistors of 10 kΩ and 2.6 kΩ. The ends of both parts are installed in thermocambric, after which they are soldered into the board.
We recommend testing the resulting circuit before assembling the device. The output voltage parameter will be 14.25 volts, which is enough to charge the battery.
Let's start assembling the device. Connect wires with clamps. Before soldering them, make sure that the output polarity is observed. Depending on the laptop unit, the negative contact can be made in the form of a central wire, and the positive contact can be made in the form of a braid.
As a result, you get a device that can properly charge the battery. The amount of current during the charge varies in the region of 2-3 amperes. If this parameter drops to 0.2-0.5 amperes, then the recharging procedure can be considered completed. For more convenient use, the charger is equipped with an ammeter, fixing it on the case. You can use an LED lamp that will tell the car owner about the completion of the charging process.

The kt819a channel provided a video that details a charger made from a laptop power supply.

How to properly charge the battery with a homemade charger?

In order to prevent a quick failure of the battery, it is necessary to take into account certain nuances for proper recharging.

First disconnect the battery terminals from the clamps. Loosen the bolts that secure the battery retainer bar.
Dismantle the device from the seat, take it home or to the garage.
Clean the body of dirt. Pay attention to the terminals themselves. If they have oxidation, they should be cleaned. Use a toothbrush or a construction brush, fine-grit sandpaper will do. The main thing is not to clean off the working plaque.
If the battery is serviceable, open all of its cans and check the electrolyte level in them. The working solution should cover all sections. If this is not the case, then charging the battery may cause the boiling liquid to evaporate rapidly, which will affect the functionality of the battery and its health as a whole. If necessary, add distilled water to the jars. Visually inspect the battery case for defects, sometimes fluid leakage is associated with cracks. If the damage is severe, the battery must be replaced.
Connect the clamps of the self-made charger to the battery terminals, observing the polarity. After that, the device can be connected to the household network. It is not necessary to unscrew the corks on the banks.
When the charging procedure is completed, check the electrolyte level and if everything is fine, then tighten the banks. Install the battery in the car and make sure it is in working order.

Conclusion

The main advantage of the device is that the car battery cannot be recharged in the process of recharging. If you forget to disconnect the battery from the charger, this will not affect its service life and will not lead to rapid wear. If you do not equip the charger with an LED indicator, you will not be able to understand whether the battery is charged or not. Alternatively, you can roughly calculate the recharging time using the readings given by the ammeter connected to the charger. You can calculate by the formula: the value of the current strength is multiplied by the charging time in hours. In practice, it takes about a day to complete the task of recharging, provided that the battery capacity is 55 Ah. If you want to visually see the level of recharging, then you can add arrow or digital indicators to the device.

You can assemble a charger from a computer power supply for a car battery yourself. And this unit is popular. After all, it requires a minimum of funds to prepare it. In this case, an effective memory is obtained.

Pay attention to the condition of the car battery in the winter. Indeed, at this time, the density of the electrolytic composition changes, the charge is quickly lost. As a result, starting the engine becomes more difficult. Chargers are used to solve this problem.

Many companies are engaged in the development and assembly of memory for batteries. Therefore, each driver will be able to choose a model with the required parameters. Such models are distinguished by extensive functionality: power source training, charge recovery, etc. Their cost is quite high.

Therefore, motorists are interested in a charger for a car battery, which is designed from improvised units and elements.

Advantages of self-assembly

Use of improvised materials, elements. Therefore, manufacturing costs are reduced.
Light weight. It does not exceed 1.5–2 kg. Therefore, it is not difficult to move a home-made unit to restore battery charge.
Constant cooling. The power supply includes a fan. Therefore, the likelihood of overheating is minimal.

What are the difficulties?

The designed converter does not always work quietly. Periodically, he makes sounds that are similar to ringing, hissing.
Contact of self-made charging and the body of the vehicle is not allowed. If we charge with inclusion in the network, then the contact provokes a breakdown of the converter, a short circuit.
The connection of the conductive terminals of the battery to the wires is accurate. If errors are made at this stage, then the secondary circuits of the converted power supply into the charger fail.
All contacts and elements are checked before connection. Only then is the computer power supply used for charging.

Rules for the operation of the car battery

To keep the car battery in working condition, it is not enough to prepare a reliable charger. Additionally, the following recommendations are made:

Continuous charge support. The battery pack is constantly being recharged. When moving, the charge comes from the generator and other vehicle components. If the equipment is not in use, then a charger is used to restore the charge, both stationary and portable. If the battery is completely discharged, then experts recommend a quick recovery. Otherwise, the process of sulfation of lead plates will start.
Voltage limits (about 14 V). The voltage supplied by the generator must not exceed this parameter excessively. In this case, it does not really matter which mode is running. If the motor is not functioning, then the voltage can drop to 12.6–13 V. With such indicators, a charger with the appropriate parameters and indicators is used.
Switching off consumers when the engine is not running. If the ignition is turned off, then all devices, headlights are turned off. Otherwise, the power supply will quickly lose charge.
Car battery preparation. Before restoring the charge from the battery, remove smudges of the electrolytic composition, dust. Conductive conclusions are cleared of oxides, plaque. Before applying voltage, the connections and wires are carefully checked. After all, even minimal shifts provoke violations, problems.
In winter, the source is moved to a warm room. After all, at a negative temperature, the electrolytic composition becomes dense, thick. This provokes a deterioration in the passage of the charge.

The main stages of manufacturing memory

Before making a reliable charger out of a computer power supply, safety requirements are studied, especially when working with such units. After all, there is voltage in the primary circuits of the PC power supply.

We prepare the power supply. The use of models differing in power is allowed. Most often, a computer PSU is reworked, the power of which is 200–250 watts.

After selecting a model, the following actions are performed:

Bolts are unscrewed from the computer power supply. Such actions are necessary for the subsequent dismantling of the cover.
Definition of the core, which is part of the pulse transformer. It is measured. The resulting value is doubled. For each element, this parameter is individual. When conducting tests, it was found that 0.95–1 cm2 is required to obtain a power of 100 W. After all, charging the power supply is effective if it produces 60–70 watts.
Many PSU models include a circuit such as TL494. A similar scheme is introduced into the composition of a variety of PSUs that are for sale.

Schema preparation

To prepare a charger from a computer power supply with your own hands, certain circuit components are required (their distinguishing feature is + 12V). All other elements are removed. To do this, use a soldering iron. To simplify the process, the schemes that are present on special portals are studied. They show the main elements that will be required for the PSU.

Circuits with indicators such as -12V, -/+5V are removed. The switch is also dismantled, with the help of which the voltage changes. The circuit that is required for the start signal is also soldered.

Making a charger from a PSU is easy. But this will require resistors (R43 and R44), which are classified as a reference type. The indicators of the resistor R43 change. If necessary, the output voltage is changed.

Experts recommend replacing R43 with 2 resistors (variable type - R432, constant type - R431). The introduction of such resistors facilitates the process of creating an adjustable element. With it, it is easier to change the current strength, as well as the output voltage. This is required to maintain the performance of the car battery.

When deciding how to remake the PSU, it is worth focusing on the capacitor. A standard capacitor is concentrated on the output part of the rectifier. Masters replace it with an element that has high voltage indicators. So, they often use a C9 capacitor.

A resistor is concentrated next to the fan, which is used for blowing. It is replaced by a resistor, which stands out with a large resistance.

When preparing the charger for the battery, the location of the fan also changes. After all, the air mass must enter the prepared power supply.

Tracks are eliminated from the circuit, which are designed to connect the mass, fix the board directly to the chassis.

The designed regulated power supply is connected to an alternating current network. For these purposes, use a standard incandescent lamp (performance is 40-100 W).

Such actions are performed in order to check how effective the scheme is. Without preliminary testing, it is difficult to determine whether a PSU will burn out with a given power during sudden voltage changes.

To properly configure a PSU for a car battery, certain rules must be observed.

Introduction of indicators. Indicators are used to keep track of how charged the car battery is. Digital or pointer indicators are introduced into the circuit. They are easy to purchase in specialized stores or dismantle from old equipment. It is allowed to introduce several indicators, with the help of which the degree of charge, the voltage on the conductive terminals is monitored.
Enclosure with mount or handles. The presence of such a part helps to simplify the process of operating the memory from the PSU.

It is allowed to assemble a memory from a power supply unit of a laptop computer, provided that there is a certain experience, knowledge in the field of electronics. Conducting any activities, if there is no appropriate preparation, is prohibited. Indeed, in the process it is necessary to contact with conductive terminals, elements to which voltage and current are applied.