How to make a charger for a 12V battery with your own hands. DIY car battery charger. Simple charger with electronic regulation

On the Internet, you can find a fairly large number of different examples of chargers, for each of them an electrical diagram of a charger for a car battery is given.

Among the many options, pulsed SMPSs attract attention, their output power can be up to 150 W, which is quite enough not only for ordinary battery charging, but also for lighting it up during engine start in difficult winter conditions.

Of course, the short-term starting current in these modes exceeds the capabilities of the charger, but even such an addition of power can significantly help a not completely infected.

The proposed circuit of a pulse charger for a car battery is not a dogma; some changes can be made to it in order to improve the output performance.

The presented circuit allows you to independently assemble a charger, which, with voltage indicators in the range of 12-14 V, can provide up to 120 A DC.

According to the fundamental characteristics, the circuit has no difficulties, the master oscillator IR2153, it easily copes with the control of two keys.

The circuit has reliable high power multi-channel field resistors IRF740. Other types of resistors can be supplied, but this will negatively affect the power output of the charger.

Description of the diagram of the charger block for the car battery

The electrical diagram of a car battery charger is a well-known half-bridge. The voltage from the mains comes after the mains filter to the rectifier; thermistors are mounted to limit the starting current.

Smoothing of inrush currents and reduction of noise level is performed by a choke and film capacitors. A bridge rectifier can be purchased or assembled of its own from four diodes of the corresponding parameters, but in all cases it is necessary to ensure that it withstands at least 400 V, and preferably all 1000 V, while the current strength should be within 6 ÷ 10 A. You can take ready-made diode assemblies from the computer power supply.

The voltage on the electrolytes of the half-bridge should be up to 250 V; at high rates, the capacitance of the capacitors must be increased accordingly. By the way, these capacitors can also be taken from the computer's power supply.

A ring transformer is used, but you can replace it with a homemade one on an E-shaped ferrite. Power transistors must have efficient heat sinks, it is better to make them separate.

In extreme cases, installation on a common heat sink is allowed. A properly assembled circuit of a pulse charger for a car battery should ensure that there is no heating of the transistors without load, if their temperature is increased, you should look for installation errors or faulty components.

For diode rectifiers, pulse rectifiers with large currents were taken; powerful diode schottky must be installed in the kit with them. An electrolytic capacitor can be placed after the bridge.

This unit does not provide protection against ultra-high short-circuit currents at the output. This means that in no case should you check the performance of the included charger by short-circuiting the wires.

If it is difficult to get rid of such a habit, then it is imperative to install an additional protection scheme, it can be installed separately or built into a common case.

Read more about the operation and repair of the car in a special section of our website.

Every motorist has a moment in his life when absolutely nothing happens by turning the key in the ignition lock. The starter did not turn, and as a result, the car did not start. The diagnosis is simple and clear: the battery is completely discharged. But having at hand even the simplest with an output voltage of 12 V, 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 the battery

Before you make a do-it-yourself battery charger, you should find out the basic rules regarding its correct charging. If you do not follow them, then the battery life will dramatically decrease and you will have to buy a new one, since it is almost impossible to restore the battery.

To establish the correct current, you need to know a simple formula: the charge current is equal to the discharge current of the battery over a period of time equal to 10 hours. This means that the capacity of the battery should be divided by 10. For example, for a battery with a capacity of 90 A / h, the charging current must be set to 9 Amperes. If you put more, the electrolyte will quickly heat up and the lead honeycomb may be damaged. With a lower current strength, it will take a very long time to fully charge.

Now you need to deal with the voltage. For batteries with a potential difference of 12 V, the charging voltage should not exceed 16.2 V. This means that for one cell, the voltage should be within 2.7 V.

The most basic rule of correct 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 the final failure of the battery.

Required tools and supplies

You can make a high-quality charger with your own hands only if there are prepared tools and consumables under these very hands.

List of tools and consumables:

• Multimeter. A must have 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.
• Soldering iron. A power of 40 or 60 watts is enough. Too powerful a soldering iron should not be taken, since the high temperature will lead to damage to dielectrics, for example, in capacitors.
• Rosin. Required for rapid temperature rise. If the parts are not heated up enough, the soldering quality will be too low.
• Tin. The main bonding material used to improve the contact of two parts.
• Heat-shrink tubing. A newer version of the old electrical tape, it is easier to use and has better dielectric properties.

Of course, tools such as pliers, a flat and curly screwdriver should always be at hand. After collecting all of the above items, you can start assembling the battery charger.

The sequence of manufacturing charging based on a switching power supply

Do-it-yourself battery charger should be not only reliable and of high quality, but also have a low cost. Therefore, the diagram below is ideal for achieving such goals.

Ready charging based on switching power supply

What you need:

• Electronic type transformer from the Chinese manufacturer Tashibra.
• Dinistor KN102. The foreign dinistor is labeled DB3.
• Power keys MJE13007 in the amount of two pieces.
• Diodes KD213 in the amount of four pieces.
• Resistor, with a resistance of at least 10 ohms and a power of 10 watts. When installing a lower power resistor, it will constantly heat up and will fail very soon.
• Any feedback transformer found in older 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 plain tin. The circuit must be isolated from the case.

An example of a charger mounted in an old system unit

The sequence of making a charger with your own hands:

• Redesign the power transformer. To do this, unwind its secondary winding, since Tashibra pulse transformers provide only 12 V, which is very small 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 over it. Only now it is necessary to make only 3 turns, the wire cross-section is at least 0.7 mm.
• Install short-circuit protection. To do this, you need the same 10 ohm resistor. It should be soldered into the gap between the windings of the power transformer and the feedback transformer.

Resistor as short circuit protection

• Solder the rectifier using four KD213 diodes. The diode bridge is simple, it can work with high frequency current, and it is manufactured according to the standard scheme.

Diode bridge based on КД213А

• Making a PWM controller. Required 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 the KT3102 type are ideal for these purposes.

PWM \u003d high quality controller

• Dock the main circuit with a power transformer and a PWM controller. After that, the resulting assembly can be fixed in a self-made case.

This charger is quite simple, does not require large assembly costs, and has a low weight. But the circuits made on the basis of pulse transformers cannot be classified as reliable. Even the simplest standard power transformer will provide more stable performance than switching devices.

When working with any charger, remember that polarity reversal must not be allowed. This charging is protected from this, but still reversed terminals will shorten the battery life, and the variable resistor in the circuit allows you to control the charge current.

Simple DIY charger

For the manufacture of this charger, you will need elements that can be found in a used old type TV. Before installing them in a new circuit, the details must be checked with a multimeter.

The main part of the circuit is the power transformer, which can not 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 must be connected to the input of the second by soldering or an ordinary terminal block.

Transformer type TS-180-2

You will also need diodes of the D242A type in the amount of four pieces. Since these elements will be collected 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 \u200b\u200bat least 25 mm2.

Only the base remains, for which you can take a fiberglass plate and 2 fuses, for 0.5 and 10A. Conductors are allowed to use any cross-section, only the input cable must be at least 2.5 mm2.

Assembly sequence of the charger:

1. The first element in the circuit is to assemble a diode bridge. It is assembled according to the standard scheme. The pins should be lowered down, and all diodes should be placed on the cooling radiators.
2. From the transformer, from terminals 10 and 10 ', lay 2 wires to the input of the diode bridge. Now it is necessary to slightly modify the primary windings of the transformers, and for this, solder a jumper between terminals 1 and 1 ′.
3. Solder the input wires to pins 2 and 2 ′. The input wire can be made from any cable, for example, from or any used household appliance. If only a wire is available, then a plug must be connected to it.
4. A 0.5A fuse should be installed in the break in the wire going to the transformer. In the gap of the positive one, which will go directly to the battery terminal - a 10A fuse.
5. The negative wire coming from the diode bridge is soldered in series to an ordinary 12 V lamp with a power not exceeding 60 W. This will help not only control the charging of the battery, 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 case, having previously placed the same fiberglass plate between it and the sheet.

Ignoring the laws of electrical engineering can result in the charger being permanently damaged. Therefore, it is worth planning in advance the charging power, depending on which and collecting the circuit. If the circuit power is exceeded, the battery will not be properly charged unless the operating voltage is exceeded.

I made this charger for charging 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, since the output voltage and output current can be adjusted within wide limits. The main components of the charger were purchased on the Aliexpress website.

These are the components:

You will also need an electrolytic capacitor of 2200 uF at 50 V, a transformer for the TS-180-2 charger (see how to solder the TS-180-2 transformer), wires, a mains plug, fuses, a radiator for a diode bridge, crocodiles. The transformer can be used with another one, with a capacity 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. A diode bridge can be recruited 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 fixed to a large radiator. It is necessary to increase the radiators of the DC-DC converter, or use a fan for cooling.

Assembling the charger

Connect the cord with a mains plug and fuse to the primary winding of the ТС-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. The alternating voltage at the terminals of the secondary winding is 14.3 volts (network voltage is 228 volts).
2. DC voltage after diode bridge and capacitor 18.4 volts (no load).

Referring to the diagram, connect a buck converter and a voltammeter to the DC-DC diode bridge.

Setting the output voltage and charging current

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

Connect the charger to the mains (nothing is connected to the output wires), the indicator will show the voltage at the output of the device, and the current is zero. Set the voltage potentiometer to 5 volts. Close the output wires together, set the short-circuit current to 6 A. with the current potentiometer. Then remove the short circuit by disconnecting the output wires and with the voltage potentiometer, 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 break of the positive wire going to the battery. Such diodes have a low voltage drop during direct connection. With this 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 when charging.

Suitable diode assemblies are used in computer power supplies. In such an assembly there are 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.

It should be borne in mind that in such assemblies, the cathode is connected to the case, 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. For this, the voltage potentiometer on the DC-DC converter board must be set to 14.5 volts measured by the multimeter directly at the output terminals of the charger.

How to charge the battery

Wipe the battery with a cloth soaked in baking soda solution, then dry. Unscrew the plugs and check the electrolyte level, if necessary add distilled water. The plugs must be turned out during charging. Debris and dirt must not get inside the battery. The room in which the battery is being charged must be well ventilated.

Connect the battery to the charger and turn on the device. During charging, the voltage will gradually rise 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.

When parked for a long time, the car battery will discharge over time. Onboard electrical equipment constantly consumes a small current, and a self-discharge process takes place in the battery. But even regular use of the machine does not always provide a sufficient charge.

This is especially noticeable in winter with 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

Lead acid batteries are used in modern cars. 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 mains. It can recharge the battery and prevent, and in some cases even reverse, the sulfation process.

A DIY battery charger (UZ) for batteries is indispensable when you leave the car in the garage for the winter. Due to self-discharge, the battery loses 15-30% capacity per month... Therefore, you cannot 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 primarily at night. Therefore, the charger should not require current and voltage control by the car owner.
• Sufficient tension. The power supply (PS) must provide 14.5V... When 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 only be reset to its original state after human intervention.
• Reverse polarity protection. If the battery terminals are incorrectly connected to the charger, the circuit should instantly turn off. The system described above copes with this task.

Common mistakes in the design of homemade storage devices

• Connecting the battery to the home power grid through a diode bridge and ballast in the form of a capacitor with a resistance. The large-capacity paper-oil capacitor required in this case will cost more than the purchased "charging". This wiring creates a large reactive load that can "to confuse" modern protection devices and electricity meters.
• Creation of a memory device 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 space technology can envy its reliability. But making such a charger for a battery with your own hands will serve as a clear illustration of the expression "Shoot the sparrows with a cannon"... And the heavy bulky design does not differ in ergonomics and ease of use.

Protection circuit

The probability that sooner or later a short circuit will occur at the output of the charger for the battery 100% ... The reason may be a polarity reversal, a loose terminal, or another operator error. Therefore, we must start with the design of the protection device (SP). It should work quickly and clearly in case of overload and break the output circuit.

There are two US designs:

• External, made as a separate module. They can be connected to any 14 volt DC source.
• Internal, integrated into the body of a specific "charging".

The classic Schottky diode circuit saves only if the battery is incorrectly connected. 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 shown in the figure. It uses relay hysteresis and the slow response of an acid battery to voltage surges.

With a load jump in the circuit, the voltage on the relay coil drops and it turns off, preventing overloading. The problem is that this circuit does not protect against polarity reversal. Also, the system does not completely shut down when the current is exceeded, and not a short circuit. When overloaded, the contacts will start to "clap" continuously and this process will not stop until they are burned. Therefore, another circuit with a pair of transistors and a relay is considered the best.

The relay coil is here connected by diodes according to the "or" logic circuit to the self-locking circuit and control modules. Before using the charger, you need to configure it by connecting a ballast load to it.

Which current source to use

A DIY charger requires a power source. The battery requires parameters 14.5-15V / 2-5A (amp hours)... Such characteristics are available for switching power supplies (UPS) and units on a transformer.

The advantage of a UPS is that it may well already be available. But the complexity of creating a charger for a battery based on it is much higher. Therefore, buying a switching power supply for use in a car charger is not worth it. It is better then to make a simpler and cheaper power supply from a transformer and a rectifier.

Battery charger circuit:

Power supply for "charging" from the UPS

The advantage of a PSU from a computer is that it already has a built-in protective circuit. However, you will have to work hard to alter the design a little. To do this, do the following:

• remove all output wires except yellow (+ 12V), black (ground) and green (PC power-on wire).
• short-circuit the green and black wires;
• install a network switch (if there is no regular one);
• find the feedback resistor in the circuit + 12V;
• replace the variable resistor with 10 kΩ;
• turn on the power supply;
• rotating the variable resistor, set at the output 14.4V;
• measure the current resistance of the variable resistor;
• replace the variable resistor with a constant of the same rating (tolerance 2%);
• connect a voltmeter to the output of the power supply to monitor the charging process (optional);
• connect the yellow and black wires in two bundles;
• connect wires with clamps to them to connect to the terminals.

Tip: You can use a universal multimeter instead of a voltmeter. Leave one red wire (+5 V) to power it.

The do-it-yourself battery charger is ready. It remains only to connect the device to the mains and charge the battery.

Charger on the transformer

The advantage of a transformer power supply is that its electrical inertia is higher than that of a battery. This increases the safety and reliability of the circuit.

Unlike a UPS, there is no built-in protection. Therefore, care must be taken to prevent overloading the DIY charger. This is also extremely important for car batteries. Otherwise, in case of overloads in current and voltage, any troubles are possible: from burnout of the windings to spilling of acid and even an explosion of the battery.

Memory from an electronic transformer (Video)

This video is about an adjustable power supply based on a converted 105W 12V electronic transformer. In combination with a pulse stabilizer module, a reliable and compact charger for all types of batteries is obtained. 1.4-26V 0-3A.

The homemade power supply consists of two blocks: a transformer and a rectifier.

You can find a finished part with suitable windings or wind it yourself. The second option is more preferable, since finding a transformer with an output 14.3-14.5 volts you are unlikely to succeed. We'll have to use ready-made solutions that give 12.6V... You can increase the voltage by about 0.6 V by assembling a mid-point rectifier on Schottky diodes.

The power of the windings must be at least 120 watt, diode parameters - 30 amps / 35 volts... This is enough to charge the battery normally.

A thyristor rectifier can be used. To obtain 14 in at the output, the input AC voltage at 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 so that it gives out 14.4V

The article will talk about how to make a homemade Scheme with your own hands, you can use absolutely any, but the simplest manufacturing option is to rework a computer power supply. If you have such a block, it will be quite easy to find its application. To power the motherboards, a voltage of 5, 3.3, 12 volts is used. As you can imagine, the voltage of 12 volts is of interest to you. The charger will allow charging batteries with a capacity ranging 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 make the alteration, you need to use the scheme presented in the article. made with your own hands from the power supply unit of a personal computer, it allows you to control the charging current and voltage at the output. You need to pay attention to the fact that there is a short circuit protection - a 10 Ampere fuse. But it is not necessary to install it, since most power supply units of personal computers have protection that turns off the device in the event of a short circuit. Therefore, the chargers for batteries from the power supply units of computers are able to protect themselves from short-circuit.

ShI controller (designated DA1), as a rule, two types of power supply are used - KA7500 or TL494. Now a little theory. Can the computer's power supply properly recharge the battery? The answer is maybe, since 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 Amperes. If the power supply has a power of more than 150 W, then its "+12 V" circuit is capable of delivering such a current.

The initial stage of rework

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 as not to interfere.
2. According to the diagram given in the article, find a constant resistor R1, which must be evaporated and replaced with a trimmer with a resistance of 27 kOhm. The upper contact of this resistor must subsequently be supplied with a constant voltage "+12 V". Without this, the device will not be able to work.
3. The 16th pin of the microcircuit is disconnected from the minus.
4. Next, you need to disconnect the 15th and 14th pins.

Quite simple, it turns out a homemade scheme, you can use any, but it is easier to make from a computer power supply unit - it is lighter, easier to operate, more affordable. If we compare with transformer devices, then the mass of the devices differs significantly (as well as the dimensions).

Charger adjustments

The back wall will now be the front one, it is desirable to make it from a piece of material (textolite is ideal). On this wall it is necessary to install a charging current regulator, indicated in the diagram R10. It is best to use a current sense resistor as high as possible - get two with 5 watts and 0.2 ohms. But it all depends on the choice of battery charger circuit. Some designs do not need power resistors.

When connected in parallel, an increase in power is obtained by two times, and the resistance becomes equal to 0.1 Ohm. There are also indicators on the front wall - a voltmeter and an ammeter, which allow you to control the corresponding parameters of the charger. To fine-tune the charger, a trimming resistor is used, with the help of which voltage is applied to the 1st pin of the SHI controller.

Device Requirements

Final assembly

Stranded thin wires must be soldered to pins 1, 14, 15 and 16. Their insulation must be reliable so that heating does not occur under load, otherwise the homemade charger for the car will fail. After assembly, you need to set the trimming resistor to a voltage of about 14 volts (+/- 0.2 V). It is this voltage that is considered normal for charging batteries. Moreover, this value should be in idle mode (without a connected load).

On the wires that connect to the battery, you must install two crocodile clips. One is red, the other is black. These can be purchased at any hardware store or auto parts store. Here is a simple homemade charger for a car battery. Connection diagrams: black is attached to minus, and red to plus. The charging process is fully automatic, no human intervention is 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 A * h, then you need to rotate the regulator until the ammeter shows 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 be maximum. As a result, at the very end, the current will be 0, and the voltage will be 14 V.

Regardless of which selection of circuits and designs of chargers was used for the manufacture, the principle of operation is in many ways 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, or even a month.

If you do not have measuring instruments that you would not mind installing 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 \u200b\u200bequal 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 a do-it-yourself battery charger, made without the use of devices, can be easily operated.