Pulse charger for cars, circuit, description

Impulse charger for a car battery with its own hands

Transformer devices are the most popular among the boosters thanks to their affordable price and simple design. However, the so-called “pulsers” also have their own niche, allowing to charge batteries of any type, with high quality and with care. If previously the use of such chargers required constant monitoring of the battery recovery process, modern pulse chargers (PSUs) for car batteries can completely exclude the presence of a person. Electronics does everything: from analyzing the state of the battery to its charging, and if necessary – to performing desulphation. Therefore, most car enthusiasts consider these devices quite promising.

What is a pulse charger?

Unlike their transformer counterparts, pulse chargers charge the battery not by a constant current of any value, but by pulses. For their formation uses a modern element base – cumbersome transformers are not required. Pulsed charging of the battery takes place in both constant current and constant voltage, plus a combined cycle. This is very important, for example, for maintenance free batteries.

Operating principle

If you look at the design, we are talking about a device that restores the charge of the car battery in a special way. The pulse charger for the car battery consists of:

  • a small pulse transformer;
  • diode rectifier;
  • stabilization unit;
  • Indication system (analog instruments or digital display);
  • The electronic module that controls the charging process.

How does a PSU work? The electronic circuit and the transformer generate a high frequency, by which the input voltage from the mains is increased. At the same time, filters (which include electrolytic capacitors) are actively used, detaining interference and smoothing the voltage at the output. Then it is converted and simultaneously decreased to the required value. A current is supplied to the battery, the value of which is controlled by additional electronic units. At the end of the process, the diode rectifier is blocked and charging stops.


All pulse chargers are uncomplicated in operation and have their own classification. In the store you will find several types of PSUs:

  1. Manual: relatively inexpensive devices that require constant control of the charging process: that is, you will have to periodically adjust U and I, monitor the time of the process.
  2. Semi-automatic: here part of the process occurs without the participation of the car owner – he only needs to consider the duration of the procedure.
  3. Automatic machines: programmable devices, capable of first determining the state of the battery, then choose the best mode of its recovery and charge with the subsequent automatic shutdown.

Full-fledged charging of the battery with a pulse device can not occur at a shock rate. It will take 14 to 20 hours to fully charge the battery.

Special charging mode

The battery can be charged with constant current, voltage or a combined mode, as will be described later. But many pulsers also have a special method of battery recovery called BOOST. This is an emergency mode that provides recharging the battery for a maximum of 10 minutes. At the end of this period, the engine will start even if the battery has been severely discharged.

But frequent use of this mode is undesirable: the constant strong impact on the electrode-plates will quickly lead to their destruction, and the battery will lose its performance finally after 2-3 months. BOOST can be used only in extreme cases: when you need to travel urgently, and the battery was discharged.

LED headlights for cars

Advantages and disadvantages

What is the reason for the popularity of pulse devices among motorists? There are quite good reasons for this:

  1. Small dimensions: some pulsers can be freely placed even in the glove compartment of the car. Therefore, the charger is easy to take with you on a long trip in severe frost, so that after the overnight stay you will not have problems with starting the engine.
  2. Ease of operation: even a person who is not sophisticated in the intricacies of electronics can figure out how to operate the device.
  3. The software in the most modern PSUs excludes human presence in the process of charging, or at least its participation is reduced to a minimum.
  4. Pulse chargers have all sorts of protection against shorts, polarity reversal, etc.
  5. The automatic mode prevents the battery from overheating and prolongs the service life of the battery.
  6. A prompting system is integrated in some PSUs. If the battery is connected incorrectly or the wrong mode is selected, an alarm and information on the display will tell what to do to properly charge the battery.

And what can be said about the negative aspects of this charger? Here we should highlight a couple of main points. The first is the relatively high cost of the device. Looking at the price, most buyers immediately go to the shelf with transformer chargers. That is why the pulsers are more often found in car service centers, service stations and private workshops.

The second is the presence of a lot of sensors, devices, complex electronic circuitry. All this helps a lot in the work process. But in case of breakage of one of these elements, the repair can cost a pretty penny. Yes, such that you may have to think about buying another device.

What chargers are there

The battery is not eternal and even in the most caring hands can serve not more than 5-6 years. But many do not make it to this, because drivers often neglect the basic rules of operation of the device. And maintenance, including. There are a lot of rules of battery maintenance, but a quality recharge is necessary for the battery even when all onboard electrical equipment is fully operational.

Current car battery chargers come in only two types:

  • pulse chargers;
  • Transformer chargers.

Transformer models of devices for all their advantages have a huge weight and dimensions. This is not a problem for those who have a full-fledged workshop, spacious garage. And in terms of reliability and stability of charging characteristics transformer dinosaurs are much better than pulse devices. But time goes on, and heavy transformers are replacing impulse devices.

How to assemble a simple pulse charger yourself

To assemble a pulse charger with your own hands is quite difficult even for a well-prepared motorist. In addition, you will have to look for electronic components, which are not available in every store. The use of used parts is also a risk, because, in fact, it is “a cat in a poke”, they will have to be tested, which requires special equipment.


It’s enough to look at the below schematic diagram of the pulse charger for a car battery, and not the most sophisticated one, to be convinced of its complexity:

Car impulse chargers made by our own hands

However, there is a way out! You can use a working power supply unit by taking it out of a dead computer. The power of the removed module must be at least 150W. But practice shows that it is safer (not to waste your time) to buy an inexpensive PSU, for example with the factory designation S-120-12. You can buy it in a well-known Chinese online store. The beauty of this product is not only that it needs minimal rework, but also that it already has factory protection against short circuits and overloads.

How to extend the life of stabilizer rods, knuckles, ball joints.

The block on the front panel already has a tweak resistance, allowing you to adjust the voltage to within 1 V. However, this is obviously not enough for the charger: you need a range of at least 9-20V. To remake the block, find a regular resistor, designated as R1, with a value of 5 kOhm in addition to the trim resistor. It should be changed to a resistance of 2.7 kOhm. In turn, the “trimmer” with the nominal value of 1 kOhm is replaced with the same resistance of 5 kOhm. Now you can adjust the voltage in the desired range. To increase PSU power, change the 1000 uF electrolytic capacitors (so called “kegs”) for the same ones, but rated not at 16V, but at 25V (they are the same size and will fit exactly into place). If you want, you can add a device to the circuit that measures current and voltage, as shown in the diagram of the pulse charger for the car battery below:

Car impulse chargers made by our own hands

Instructions for making a car battery charger with your own hands

A simple circuit for making a car battery charger

You can make a charger for car batteries at home, consider the process of making a device with the circuit IR2153. In this circuit there are no two capacitor elements connected to the midpoint, instead of them installed electrolyte. According to this scheme you can make a device which is originally designed for low power, but if you want to get a more powerful charger, you can slightly modify the circuit by adding powerful components.

  1. The circuit of the pulse charger uses 8N50 switches which are equipped with a protective shield. You will also need diode bridges, you don’t need to buy them in a store but you can get them from an old PC power supply. If you can’t get such diodes, in principle you can make the bridge from rectifier diodes, you need four of them.
  2. Equally important is the arrangement of the power supply circuit, for the implementation you will need a resistor element to damp the current, the best option would be a resistor of 18 kOhm. Behind the resistor component is a rectifier, which is mounted on a diode. In this case, the power from the domestic mains will be transferred to the board, this is suitable for us. On the power supply itself it will be necessary to install an electrolyte, and it will also need to be connected to the capacitor element – you can use a ceramic device or a film device. It is mandatory to add a capacitor to the circuit, as this will smooth out any possible interference in the operation of a surge protector as much as possible.
  3. The transformer unit can be taken from an old computer power supply, it is important to make sure that it works. Devices that are put in power supply units are optimal for making a battery charger, because they give a good current output. The diode elements of the transformer should in any case be pulsed, as conventional parts will not be able to work under high frequency conditions.
  4. As for the filter element, its use is not mandatory, but it is still possible to add a filter. You can also add a 5 ohm thermistor to the circuit and install it in front of the filter, this will achieve maximum noise reduction. By the way, you can also remove the thermistor from a computer power supply.
  5. Don’t forget to install an electrolytic capacitor component as well, you should use a 1 W – 1 uF ratio when choosing one (the author of a video about step-by-step making of a regulator is Soldering iron TV channel).
Transformer charger with your own hands

At first glance this circuit may seem quite complicated, but in general there is nothing complicated about it. If you do everything correctly and take into account all the points and recommendations, the manufacturing process will not cause difficulties, even if you have never faced with this task before.

Photo gallery “Schemes for making ZU”.

Below are more complicated circuits for making chargers. If you have the skills, you can use these circuits.

A more complicated circuit for a surge charger

2. A powerful surge charger circuit

What do the owner of such a device need to know?

The features of the homemade device, assembled according to the circuit of pulse charger, given above, are not so many, the process itself is not complicated, the control over it is reduced to a minimum. Electronic protection eliminates the failure of components at improper connection or overload in the network.

How to charge properly

Connect the PSU to the 220 V mains, turn the switch to the operating position. When the device, which measures current and voltage, is working, turn the trimmer knob to the left all the way: you will get 9 V at the output. Now connect the output wires to the battery terminals, matching (+) and (-). Use an alternating resistor to slowly increase the voltage to 13.5 volts (if the battery is completely dead) or 14.5 volts (if the battery is about 50% dead). Look at the ammeter: I should be 10% of the capacity. For example, for a 55 Ah battery this would be 5.5 A.

As the process goes on, the amperage will drop and the density of the electrolyte will increase. The procedure may be considered complete when I = 0.1 A or less.

How does the protection function?

If the output wires are accidentally shorted, the PSU will remain operational: It will simply turn off. Remove the plug from the mains, remove the cause of the short circuit, and the unit is ready to use again. There is also an overload protection: the device is triggered when a current of 10 A appears. As soon as such a value occurs, the device automatically shuts down.

Frequently made mistakes

First of all, it is a rush. You can not fully charge the battery of a PSU in 4-5 hours. It will take at least 14 hours. Especially if the process is carried out in sub-zero temperatures. It is also recommended to look carefully at the poles when connecting the battery: not every battery charger has “foolproof” protection. If you have a lead-acid battery, serviceable, for the period of charging it is worth to unscrew (maybe half) the plugs of the cans. Protect the device from the penetration of moisture, the formation of condensation. Condensation can settle on the case when you take the charger from frost to a warm room. In this case you can start using the device in a couple of hours, when the moisture deposited on the electronic components has dried.

Interior wood laminate with my own hands

Typical PU failure and their repair

One of the most common defects that usually appear after a year or two of operation is the lack of voltage at the output. In the best case the cause is a blown fuse: you just need to replace it. If it is faulty, examine the PCB: first of all pay attention to the electrolytic capacitors – their bloating indicates the failure.

However, you should not limit yourself to replacing them only: breakage of capacitors could lead to failure of other elements according to the chain principle. Therefore, it is necessary to unsolder and check:

  • rectifier diode bridge;
  • filter capacitors;
  • Field effect transistors (they are on aluminum heat sinks).

Also don’t forget to check the continuity of the power wires and the functionality of the switch. If you do not have on hand the right fuse, it can be temporarily replaced by a “bug”: a wire cross section of 0.11 mm corresponds to a current of 3 A.

The most popular models

Among the most popular SPDs are devices made in Russia, Italy, Germany, China, Ukraine and other countries. Below are devices from the budget segment:

  1. Voin VL 156-6(12)V. Equipped with a digital display, thanks to which the process is under control. There are several charging modes and electronic protection of 3 levels. The dimensions are compact and the price is affordable.
  2. Elegant. Holds static voltage for a long time. Realizes slow, gentle charging. All processes are shown on the digital monitor.
  3. Master Watt. Universal device which can confidently work with any type of accumulators. Since it is semi-automatic, it requires uncomplicated control. The manufacturer assures a long service life – up to 25 years.
  4. KeePower Medium. Fully automatic device. It is enough to simply connect the device to the battery and set the required program. The battery will be charged slowly, quickly or at a medium rate.

As you can see, pulse chargers are becoming more and more common on the market. Obviously, with time, when the competition will be stronger, the price of the products will fall. And if you do not want to wait, you can try to build a pulse charger with your own hands. It will surely be cheaper.

Pulse charger for cars, circuit, description

car battery charger

Here is a simple circuit of impulse charger for car battery, compact, tested in work and with all the protections.

 car battery charger

The electronic transformer is slightly modified, so that eventually the output is 14 volts, that is, if there is no 14 volts, it is necessary to wind up the secondary winding a little. Then we add (optional) surge protector. Make sure to make a diode rectifier and protection circuits against short circuits, polarity reversal and overload. And add a display.

 winding the secondary winding

 car battery charger, schematic

I took a Chinese electronic transformer for 80 watts. The frequency is set by a DB3 diistor around 30kHz. There are 2 transformers, one is the OS, the second (main) is a step down transformer.

. MJE 13005 keys were taken.

The 3 windings contain the OS transformer, the two basic key windings and the OS winding itself. MJE 13005 keys were used.

To be able to use our charger also as a PSU, we are going to switch it on without load.

So, what is needed for this….

1) Unwire the OS winding and make a jumper in its place. 2) Wound 2 turns of 0.4mm wire on the main transformer and connected the whole thing as shown in the schematic below. It is not necessary if this device will work only as a battery charger.

Stereo amplifier circuit based on TA8205, TA8210, TA8215, TA8221 chips

The resistor should be 5-10 watts and it will always be warm, but that’s okay.

This modification gives us protection against short circuit and switching the system on without load. But anyway in case of long-lasting short circuit (more than 10 sec) the keys can fail, so we will make a separate short-circuit protection.

We will make it on a separate board.

Six 0.1 ohm resistors,

The circuit uses an IRFZ44 transistor, you can use a bigger one IRF3205. You can use switches for more than 20 amps, such as IRFZ24, IRFZ40, IRFZ46, IRFZ48 etc. A heat sink is not needed for the field effector. The choice of the second transistor is not critical, I took the bipolar MJE13003, but the choice is yours. Six 0.1 ohm resistors connected in parallel set the shunt resistance to match the protection current. This way the protection current will trip at 6 or 7 amps. You can also adjust the tripping current with a variable resistor.

car pulse charger, circuit, description

The output current of the PSU goes up to 7 amps, pretty decent. I took a 5 watt shunt resistor, but it can handle 2 or 3 watts.

car pulse charger, circuit, description car pulse charger, circuit, description car pulse charger, circuit, description

Now I need to change the output voltage was 14 volts instead of 10-12 volts.

This is done simply on the secondary winding add only 3 turns and this increase the voltage by three volts. It is not necessary to disassemble the core itself. Wire took a section of 1 mm and connect, or rather solder our winding at one end to the factory, and the other end is the output. (That is in series)

Now let’s get to the rectifier.

I took the diodes from a computer PSU and soldered them out. You need three identical assemblies. Make sure the diodes are pulsed or ultra-fast and not less than 10 amps. Our type KD213 and similar will also do.

Diodes took schottky,

We assembled the bridge, the blocks in a pile and connected to 220, to prevent the circuit from burning (in case of a mess up) it should be connected through an ordinary 60-100 watt light bulb, which we connect in series with our circuit.

When the block is properly assembled, it works at once, now we short circuit the output on it, the LED lights up (this indicates a short circuit).

Now we assemble the circuit of the indicator

 make a circuit indicator

The circuit itself is taken from a screwdriver battery charger. Where the green light shows you that the battery is charging and the red shows you that there is voltage at the output of the power supply.

The green light will fade gradually and after 12.4 volt it will go out completely.

Green indicator

The surge protector

But now all we have to do is the surge protector, it will consist of 2 film capacitors and a choke.

 two separate windings

The capacitors are connected before and after the choke. The choke can be taken from a UPS or you can wind it yourself. Take a ring and wind two separate windings, 20 turns each with 0.5 mm wire. Capacitors of 0.47 μF 250 or 400 volts, it is better to use film capacitors. Now we assemble everything into the case and enjoy a full-fledged pulse charger. If you want, you can also make a power regulator.

car pulse charger, circuit, description car pulse charger, circuit, description

 more powerful transformers.

More powerful transformers can be used in the device. Practice has shown the reliability of this device and its easy construction. Author; AKA Kasyan

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