The article will talk about how to make a home-made charger for a car battery with your own hands . You can use absolutely any schemes, but the easiest production option is alteration of a computer PSU. If you have such a unit, it will be quite simple to find an application for it. A voltage of 5, 3.3, 12 Volts is used to power the motherboards. As you know, the interest for you is the voltage of 12 volts. The charger will allow you to charge batteries whose capacity is in the range from 55 to 65 ampere hours. In other words, it is enough to recharge the batteries of most cars.
General view of the circuit
To alter, you need to use the scheme presented in the article. A self-made charger for the battery from the PSU of a personal computer allows you to control the charging current and voltage at the output. It is necessary to pay attention to the fact that there is protection against short-circuit - a fuse of 10 amperes. But it is not necessary to install it, since in most PSUs of personal computers there is protection that disconnects the device in the event of a short circuit. Therefore, the circuit charger for batteries from PSU computers are able to protect themselves from short circuit.
A SI controller (designated DA1), as a rule, two types of PS are used in the PSU - KA7500 or TL494. Now a little theory. Can a computer power supply recharge normally? The answer is maybe, since lead batteries of most cars have a capacity of 55-65 ampere-hours. And for normal charging, he needs a current equal to 10% of the battery capacity - not more than 6.5 Amps. If the power supply has a power exceeding 150 W, then its “+12 V” circuit is capable of delivering such a current.
The initial stage of the alteration
To repeat a simple home-made battery charger, you need to slightly improve the power supply:
- Get rid of all unnecessary wires. Using a soldering iron, remove them so that they do not interfere.
- According to the circuit shown in the article, find the constant resistor R1, which must be soldered out and install a trimmer with a resistance of 27 kΩ in its place. Subsequently, a constant voltage of “+12 V” must be applied to the upper contact of this resistor. Without this, the device will not be able to work.
- The 16th pin of the chip is disconnected from the minus.
- Next, you need to disconnect the 15th and 14th conclusions.
It turns out pretty simple homemade charger for a car battery. Any schemes can be used, but it is easier to make from a computer PSU - it is easier, easier to operate, more affordable. When compared with transformer devices, the mass of devices is significantly different (as are the dimensions).
Charger Adjustments
The back wall of the computer power supply will now be the front, it is desirable to make it from a piece of material (textolite is ideal). On this wall, it is necessary to install the charge current regulator indicated on the R10 diagram. A current measuring resistor is best used as powerfully 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 battery charger design. Some designs do not need to use powerful resistors.
When they are connected in parallel, a twofold increase in power is obtained, and the resistance becomes 0.1 Ohm. On the front wall there are also indicators - a voltmeter and an ammeter, which allow you to control the corresponding parameters of the charger. To fine-tune the charger, a tuning resistor is used, with which voltage is applied to the 1st output of the SHI controller.
Device requirements
What are the requirements of a homemade car battery charger? Final assembly schemes will be discussed below. To eliminate the unwanted connection of the power supply housing 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 metal casing, but for safety reasons it is not possible that the battery charging circuit has a galvanic connection with it. And the most important thing is the exclusion of the parasitic circuit of the charging current (bypassing the resistor R11). During operation, do not confuse the terminals - this will damage the charger.
Final assembly
To 1, 14, 15 and 16 conclusions you need to solder stranded thin wires. Their insulation must be reliable so that heating does not occur under load, otherwise a homemade charger for the car will fail. After assembly, you need to set a trimmer with a voltage of about 14 volts (+/- 0.2 V). This voltage is considered normal for charging batteries. Moreover, this value should be in idle mode (without connected load).
On the wires that connect to the battery, you must install two crocodile clips. One is red, the second is black. Such can be bought at any household goods store or automotive parts. Here it turns out a simple home-made charger for a car battery. Connection diagrams: black is attached to the minus, and red to the plus. The charging process is fully automatic, no human intervention is required. But it is worth considering the main stages of this process.
Battery Charge Process
At the initial cycle, the voltmeter will show a voltage of about 12.4-12.5 V. If the battery has a capacity of 55 A * h, then you need to rotate the regulator until the ammeter shows a value of 5.5 Amps. This means that the charging current is 5.5 A. As the battery charges, the current decreases and the voltage tends to the maximum. As a result, at the very end, the current will be 0, and the voltage 14 V.
Regardless of which selection of circuits and designs of chargers were used for the manufacture, the principle of operation is largely similar. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not run the risk of overcharging the battery. Therefore, the charger can be connected to the battery for a day, a week, and even a month.
Tips for repeating
If you do not have measuring devices that would not be a pity to install in the device, you can refuse them. But for this it is necessary to make a scale for the potentiometer - to indicate the position for the charging current values of 5.5 A and 6.5 A. Of course, the installed ammeter is much more convenient - you can visually observe the progress of charging the battery. But even a charger for the battery, made without the use of appliances, can be easily operated.