Homemade battery charger for car battery: circuits, instructions

The article will tell you how to make a self-made battery charger for your car battery with your own hands . Schemes you can use absolutely any, but the simplest version of manufacturing is the redesign of the computer PSU. If you have such a unit, it will be easy to find an application. To power the motherboard uses a voltage of 5, 3.3, 12 volts. As you understand, the interest for you is the voltage of 12 volts. The charger will allow charging batteries with a capacity between 55 and 65 ampere hours. In other words, it is enough to recharge the batteries of most cars.

General view of the circuit

To make an alteration, you need to use the scheme presented in the article. Charger for the battery, with their own hands from the BP of a personal computer manufactured, allows you to monitor the output of the charging current and voltage. It should be noted that there is a short-circuit protection - a 10 amp fuse. But it is not necessary to install it, since in most PSUs there is protection, which turns off the device in the event of a short-circuit. Therefore, the charger circuits for the batteries from the PSU computers are able to protect themselves from short circuit.

The SHI controller (designated DA1), as a rule, two types of KA7500 or TL494 are used in the PSU. Now a bit of theory. Can the computer power supply be recharged normally? The answer is maybe because the lead batteries of most cars have a capacity of 55-65 Ampere-hour. And for normal charging it needs a current equal to 10% of the battery capacity - no more than 6.5 Amps. If the power supply unit has a power of more than 150 W, then its "+12 V" circuit is capable of delivering such a current.

The initial stage of the alteration

To replicate a simple homemade battery charger, you need to slightly improve the power supply:

1. Get rid of all unnecessary wires. Use a soldering iron to remove them so they do not interfere.
2. According to the scheme given in the article, find a constant resistor R1, which must be evaporated and a tuning resistor with a resistance of 27 kΩ should be installed in its place. On the upper contact of this resistor, then you need to apply a constant voltage of "+12 V". Without this, the device will not work.
3. The 16th pin of the microcircuit is disconnected from the minus.
4. Next, you need to disconnect the 15th and 14th conclusions.

Quite simply, you get a homemade battery charger for a car battery. Schemes can be used any, but it is easier to make out of a computer BP - it is easier, easier to operate, more accessible. If to compare with transformer devices, the mass of the devices is significantly different (as well as the dimensions).

Charger settings

The rear wall of the computer power supply will now be front, to make it preferably from a piece of material (textolite is ideal). On this wall, it is necessary to install a charging current regulator, indicated on the circuit R10. The current-carrying resistor is best used as much as possible - take two with a power of 5 watts and a resistance of 0.2 ohms. But it all depends on the choice of the charger circuit for the batteries. In some designs, you do not need to use powerful resistors.

When they are connected in parallel, an increase in power is obtained by a factor of two, and the resistance becomes 0.1 Ω. On the front wall are also located indicators - voltmeter and ammeter, which allow you to monitor the relevant parameters of the charger. To fine-tune the charger, a trimmer is used to supply voltage to the 1st pin of the controller.

Requirements for the device

What are the requirements of a self-made battery charger for a car battery? The final assembly plans will be discussed below. To eliminate the unwanted communication between the power supply enclosure and the common wire of the charging circuit (the part that was assembled by you), you need to remove the printed tracks. The power supply has a housing made of metal, and for safety reasons it is not possible for the battery charging circuit to have a galvanic connection with it. And the most important thing is the elimination of the parasitic circuit of the charging current (bypassing the resistor R11). During operation, it is impossible to confuse the terminals - this will disable the charger.

Final assembly

To 1, 14, 15 and 16 leads, soldered stranded wires must be soldered. The insulation should be reliable, so that under the load there is no heating, otherwise the homemade battery charger for the car will fail. After assembly, you need to install a trimmer resistor voltage of about 14 volts (+/- 0.2 V). It is this voltage that is considered normal for charging the batteries. And this value should be in idle mode (without connected load).

On the wires that connect to the battery, you need to install two crocodile clips. One is red, the other is black. These can be bought in any store of household goods or car parts. Here is a simple self-made battery charger for a car battery. Connection diagrams: black is attached to the minus, and red to the plus. The charging process is fully automatic, human intervention is not required. But it is worth considering the main stages of this process.

Battery charging process

At the initial cycle, the voltmeter will show a voltage of approximately 12.4-12.5 V. If the battery has a capacity of 55 Ah, then you need to rotate the regulator until the ammeter shows a value of 5.5 amperes. This means that the charging current is 5.5 A. As the battery is charged, the current decreases and the voltage tends to a maximum. As a result, at the very end, the current will be 0, and the voltage will be 14 V.

Regardless of the type of circuit and charger design used for the manufacture, the principle of operation is similar in many respects. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not run the risk of recharging the battery. Therefore, the charger can be connected to the battery for a day, a week, or even a month.

Tips for repeating

If you do not have any measuring devices that you would not like to install in your device, you can refuse them. But for this it is necessary to make a scale for the potentiometer - to indicate the position for charging current values equal to 5.5 A and 6.5 A. Of course, the installed ammeter is much more convenient - you can visually observe the process of charging the battery. But the battery charger, built with your own hands without the use of instruments, can easily be used.