DIY charger for a 12V car battery. Homemade car battery charger

A homemade charger can come in handy if your battery runs out and you don’t have a normal electrical appliance at hand. Making it yourself is quite simple, you just need to have a few basic elements of the chain. Next, we will take a detailed look at the homemade device, as well as instructions on how to make a battery charger with your own hands.

Homemade device

So, to assemble the charger we need the following elements:

• Power transformer. A part from an old TV would be ideal. Usually transformers TS-180-2 are installed, so we will consider it in the article.
• Fiberglass plate.
• Diodes D242A - 4 pcs., you can use products of other markings, but they must be rated for a current of more than 10 A.
• Radiators for the diode - 4 pcs., area 25 cm 2 (or better 32 cm 2).
• Demountable electrical plug.
• Copper wires with a cross section of no less than 2.5 mm 2
• 10 A and 0.5 A fuse.
• Soldering iron.

Having prepared all the materials, you can proceed to the process of assembling the car charger itself.

Assembly technology

To make a charger for car battery do it yourself, you need to follow the step-by-step instructions:

1. We create a homemade battery charging circuit. In our case it will look like this:
   
2. We remove the secondary windings of the TV transformer (the primary must be left) and connect them in series in the circuit. As a result, you should get 12.8 V at the output, because The voltages of the secondary windings are 6.4 V and 4.7 V.
   
3. Using a copper wire, we connect pins 9 and 9’ to each other.
   
4. On a fiberglass plate we assemble a diode bridge from diodes and radiators (as shown in the photo).
   
5. We connect pins 10 and 10’ to the diode bridge.
6. We connect the primary windings of the TS-180-2 television transformer in series.
7. We install a jumper between pins 1 and 1’.
   
8. Using a soldering iron, attach a power cord with a plug to pins 2 and 2’.
9. We connect a 0.5 A fuse to the primary circuit, and a 10-amp fuse to the secondary circuit, respectively.
10. We limit charging current, connecting a 12-volt light bulb to the neutral conductor gap, in series with the battery itself. The power should vary between 21-60 W.

A visual example of the finished product

Operating rules

The disadvantage of a homemade 12V battery charger is that after fully charged The battery does not automatically switch off. That is why you will have to periodically glance at the scoreboard in order to turn it off in time. Another important nuance– checking the charger “for spark” is strictly prohibited.

Among additional measures The following precautions should be noted:

• when connecting the terminals, make sure not to confuse “+” and “-”, otherwise a simple homemade battery charger will fail;
• connection to the terminals should only be made in the off position;
• The multimeter must have a measurement scale greater than 10 A.

There are a lot of people in Lately ask you to write an article or film a video review about the most simple charger for a car battery. I decided to write an article and film a video so that questions related to charging car batteries would not arise.

At the same time, users are asked to provide the design of the simple option. Of course, you can whip up a charger for a car, but without galvanic isolation from a 220 Volt network, this is very dangerous and it is not advisable to always charge the battery with such a charge (we will look at a general collection of quick chargers in the next article).

The cheapest power supply is definitely an electronic transformer. Now in stores such a 60-80 watt unit costs only one dollar. 60 watts is quite a lot of power, it turns out to be about 4-5 Amperes of current at a voltage of 14 Volts - it’s quite possible to charge the battery!

The electronic transformer has no protection, so do not short-circuit the output wires, otherwise it will be bad (at best a bang, at worst - shrapnel wounds with serious consequences).

• The second drawback is that the unit does not turn on without an output load.
• The third drawback is the output voltage is variable - 15 kHz
• The fourth drawback is that the output voltage is 8-10 Volts, which is not enough to charge a car battery.

These problems can be fixed in half an hour. First, let's add protection from short circuit and a system for turning on the unit without an output load, and also increase the output voltage to 14 Volts.

We need wirewound resistor 3-10 Ohms, the higher the rating, the lower the protection operation current, I advise you to use a 3-6 Ohms resistor.

We take a 0.8mm wire, fold it into 4 cores and wind a new winding on the transformer frame. The winding consists of 12-14 turns.

After that, we wind a separate winding in the same direction - only 3 turns with 0.8 mm wire (the wire is not critical -0.4-0.8 mm).

We look at the transformer board and find the OS transformer ( Feedback). It is in the form of a small ring and consists of 3 independent windings - 2 of them are the base windings of transistors, 3 turns each winding. The third winding, the OS winding, consists of only one turn. We unsolder this winding and replace it with a jumper. Next, on the same ring we wind 2 turns of 0.8mm wire and connect the OS resistor in series; we make the connection according to the photo.

Everything is ready - this modification has implemented short-circuit protection at the output, increased the output voltage of the block and the block is now turned on without an output load. All that remains is to add a diode rectifier and a smoothing capacitor after the rectifier. It is advisable to assemble a full-fledged diode bridge from KD213 diodes, but of course any other ones are possible pulse diodes with a current of at least 4-5 A, preferably 10 Amperes or more.

Electrolyte at 1000 uF (You can use 470-2200 uF, or you can remove it altogether)

The output voltage is about 14.5 Volts. We connect the unit to a 220 Volt network and measure the voltage. Next we connect the battery to charge BUT! necessarily through an ammeter. If the current is more than 4 Amps, then we connect a 5-10 watt resistor with a resistance of 0.5-2.2 Ohms in series to one of the power buses (plus or minus) - the resistor must be selected until we get a charge current of about 4A (3. 5-4A). This is necessary so that the unit does not overload and fail.

Finally, some safety tips.

Always connect the electronic transformer to a 220 Volt network in series through a 220 Volt 40-100 watt incandescent lamp, this will avoid explosions if installed incorrectly.

Do not short-circuit the output wires of the electronic transformer. During tests, do not touch the device board when the transformer is connected to a 220 Volt network. Be extremely careful during testing to avoid tragic consequences.

In the video clip he spoke in detail about the rework, if anyone is too lazy to read the article, but is still interested, then watch the video - see you again on the pages of the site - AKA KASYAN

Every owner of a used car is faced with the need to recharge the battery. Besides, rechargeable batteries often used as a backup (or main) source of electricity in a garage, barn, or country house without a centralized electricity supply.

To restore the battery charge, you can purchase a ready-made one; there is no shortage of options.

Used to charge car battery

However, many home craftsmen prefer to make their own. If you have a radio engineering background, you can calculate the circuit yourself. And for the majority of hobbyists who know how to hold a soldering iron in their hands, we offer a couple of simple designs.

First of all, let's decide which batteries you need to charge. As a rule, these are acid starter batteries used in cars.

Such a battery can be purchased inexpensively at a car store, or you can use an old one left over from replacing it in your car. a used one may not be able to work as a starter, but it’s easy to connect a lighting device (especially LED) or a radio in the country to it.

How to correctly calculate a homemade charger?

The first rule that needs to be learned is the value of the charge voltage.
Lead-acid batteries have an operating voltage of 12.5 volts. But to charge, you need to apply a voltage in the range of 13.9 - 14.4 volts. Accordingly, the charger must be made with exactly these output parameters.

The next quantity is power.
More precisely, the current strength at which there will be no voltage drop at the output terminals of the charger. If you do not plan to charge batteries with a capacity of more than 65 Ah, a stable current of 12 A is sufficient.

Important! This value must be provided by the output stage of the charger; the current at the 220 volt input will be several times less.

A low-power charger can also charge high-capacity batteries. It will just take much more time.

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. 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:

1. AC voltage at the terminals of the secondary winding 14.3 volts (mains voltage 228 volts).
2. Constant pressure after the diode bridge and capacitor 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 at direct connection. 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 paralleled. 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.

Now there is no point in assembling a charger for car batteries yourself: in stores huge selection ready-made devices, their prices are reasonable. However, let’s not forget that it’s nice to do something useful with your own hands, especially since a simple charger for a car battery can be assembled from scrap parts, and its price will be a pittance.

The only thing you should immediately warn about is that circuits without precise regulation of the current and voltage at the output, which do not have a current cutoff at the end of charging, are suitable for charging only lead-acid batteries. For AGM and the use of such charges leads to damage to the battery!

How to make a simple transformer device

The circuit of this transformer charger is primitive, but functional and assembled from available parts - the simplest type of factory chargers are designed in the same way.

At its core, it is a full-wave rectifier, hence the requirements for the transformer: since the voltage at the output of such rectifiers is equal to the rated voltage alternating current, multiplied by the root of two, then at 10V on the transformer winding we get 14.1V at the output of the charger. You can take any diode bridge with a direct current of more than 5 amperes or assemble it from four separate diodes; a measuring ammeter is also selected with the same current requirements. The main thing is to place it on a radiator, which in the simplest case is an aluminum plate with an area of ​​at least 25 cm2.

The primitiveness of such a device is not only a minus: due to the fact that it has neither adjustment nor automatic shutdown, it can be used to “reanimate” sulfated batteries. But we must not forget about the lack of protection against polarity reversal in this circuit.

The main problem is where to find a transformer of suitable power (at least 60 W) and with a given voltage. Can be used if a Soviet filament transformer turns up. However, its output windings have a voltage of 6.3V, so you will have to connect two in series, winding one of them so that you get a total of 10V at the output. An inexpensive transformer TP207-3 is suitable, in which the secondary windings are connected as follows:

At the same time, we unwind the winding between terminals 7-8.

Simple electronically regulated charger

However, you can do without rewinding by adding an electronic output voltage stabilizer to the circuit. In addition, such a circuit will be more convenient for garage use, since it will allow you to adjust the charge current during power supply voltage drops; it is also used for small-capacity car batteries, if necessary.

The role of the regulator here is played by the composite transistor KT837-KT814, the variable resistor regulates the current at the output of the device. When assembling the charger, the 1N754A zener diode can be replaced with the Soviet D814A.

The adjustable charger circuit is easy to replicate and can be easily assembled by wall mounting without the need for etching. printed circuit board. However, please note that field effect transistors placed on a radiator, the heating of which will be noticeable. It is more convenient to use an old computer cooler by connecting its fan to the outputs of the charger. Resistor R1 must have a power of at least 5 W; it is easier to wind it from nichrome or fechral yourself or connect 10 one-watt 10 ohm resistors in parallel. You don’t have to install it, but we must not forget that it protects the transistors in the event of a short circuit.

When choosing a transformer, focus on an output voltage of 12.6-16V; take either a filament transformer by connecting two windings in series, or select a ready-made model with the desired voltage.

Video: The simplest battery charger

Remaking a laptop charger

However, you can do without searching for a transformer if you have an unnecessary laptop charger at hand - with a simple modification we will get a compact and lightweight switching power supply capable of charging car batteries. Since we will need to get an output voltage of 14.1-14.3 V, neither ready block power supply will not work, but the modification is simple.
Let's look at a section of a typical circuit according to which devices of this kind are assembled:

In them, maintaining a stabilized voltage is carried out by a circuit from the TL431 microcircuit that controls the optocoupler (not shown in the diagram): as soon as the output voltage exceeds the value set by resistors R13 and R12, the microcircuit lights up the optocoupler LED, tells the PWM controller of the converter a signal to reduce the duty cycle of the supplied to the pulse transformer. Difficult? In fact, everything is easy to do with your own hands.

Having opened the charger, we find not far from the output connector TL431 and two resistors connected to the Ref. It is more convenient to adjust the upper arm of the divider (resistor R13 in the diagram): by decreasing the resistance, we reduce the voltage at the output of the charger; by increasing it, we raise it. If we have a 12 V charger, we will need a resistor with a higher resistance, if the charger is 19 V, then with a smaller one.

Video: Charging for car batteries. Protection against short circuit and reverse polarity. With your own hands

We unsolder the resistor and instead install a trimmer, pre-set on the multimeter to the same resistance. Then, having connected a load (a light bulb from a headlight) to the output of the charger, we turn it on to the network and smoothly rotate the trimmer motor, while simultaneously controlling the voltage. As soon as we get the voltage within 14.1-14.3 V, we disconnect the charger from the network, fix the trimmer resistor slide with nail polish (at least for nails) and put the case back together. It will take no more time than you spent reading this article.

There are more complex circuits stabilization, and they can already be found in Chinese blocks. For example, here the optocoupler is controlled by the TEA1761 chip:

However, the setting principle is the same: the resistance of the resistor soldered between the positive output of the power supply and the 6th leg of the microcircuit changes. In the diagram shown, two parallel resistors are used for this (thus obtaining a resistance that is outside the standard range). We also need to solder a trimmer instead and adjust the output to the desired voltage. Here is an example of one of these boards:

By checking, we can understand that we are interested in the single resistor R32 on this board (circled in red) - we need to solder it.

There are often similar recommendations on the Internet on how to make a homemade charger from computer unit nutrition. But keep in mind that all of them are essentially reprints of old articles from the early 2000s, and such recommendations are not applicable to more or less modern power supplies. In them it is no longer possible to simply raise the 12 V voltage to the required value, since other output voltages are also controlled, and they will inevitably “float away” with such a setting, and the power supply protection will work. You can use laptop chargers that produce a single output voltage; they are much more convenient for conversion.