Three simple current regulator circuits for chargers. Charger for ku202. Simple charger Car charger based on thyristor

Often car owners have to deal with the phenomenon of the inability to start the engine due to a low battery. To solve the problem, you will need to use a battery charger, which costs a lot of money. In order not to spend money on buying a new charger for a car battery, you can make it yourself. It is only important to find a transformer with the necessary characteristics. To make a homemade device, you don’t have to be an electrician, and the whole process will take no more than a few hours.

Features of battery operation

Not all drivers know that lead-acid batteries are used in cars. Such batteries are distinguished by their endurance, so they can last up to 5 years.

To charge lead-acid batteries, a current equal to 10% of the total battery capacity is used. This means that to charge a battery with a capacity of 55 A/h, a charging current of 5.5 A is required. If a very high current is applied, this can lead to boiling of the electrolyte, which, in turn, will lead to a decrease in service life devices. A small charging current does not extend the life of the battery, but it does not have a negative impact on the integrity of the device.

This is interesting! When a current of 25 A is supplied, the battery is quickly recharged, so within 5-10 minutes after connecting a charger with this rating, you can start the engine. Such a high current is produced by modern inverter chargers, but it negatively affects the battery life.

When charging the battery, the charging current flows back to the working one. The voltage for each can should not be higher than 2.7 V. A 12 V battery has 6 cans that are not connected to each other. Depending on the battery voltage, the number of cells differs, as well as the required voltage for each cell. If the voltage is higher, this will lead to a process of decomposition of the electrolyte and plates, which contributes to the failure of the battery. To prevent the electrolyte from boiling, the voltage is limited to 0.1 V.

The battery is considered discharged if, when connecting a voltmeter or multimeter, the devices show a voltage of 11.9-12.1 V. Such a battery should be recharged immediately. A charged battery has a voltage at the terminals of 12.5-12.7 V.

Example of voltage at the terminals of a charged battery

The charging process is the restoration of spent capacity. Charging batteries can be done in two ways:

1. D.C. In this case, the charging current is regulated, the value of which is 10% of the device capacity. Charging time is 10 hours. The charging voltage varies from 13.8 V to 12.8 V for the entire charging duration. The disadvantage of this method is that it is necessary to control the charging process and turn off the charger in time before the electrolyte boils. This method is gentle on the batteries and has a neutral effect on their service life. To implement this method, transformer chargers are used.
2. Constant pressure. In this case, a voltage of 14.4 V is supplied to the battery terminals, and the current changes from higher to lower values ​​automatically. Moreover, this change in current depends on such a parameter as time. The longer the battery is charged, the lower the current becomes. The battery will not be able to be recharged unless you forget to turn off the device and leave it for several days. The advantage of this method is that after 5-7 hours the battery will be charged by 90-95%. The battery can also be left unattended, which is why this method is popular. However, few car owners know that this charging method is “emergency”. When using it, the service life of the battery is significantly reduced. In addition, the more often you charge in this way, the faster the device will discharge.

Now even an inexperienced driver can understand that if there is no need to rush to charge the battery, then it is better to give preference to the first option (in terms of current). With accelerated charge recovery, the service life of the device is reduced, so there is a high probability that you will need to buy a new battery in the near future. Based on the above, the material will consider options for manufacturing chargers based on current and voltage. For production, you can use any available devices, which we will discuss later.

Battery charging requirements

Before carrying out the procedure for making a homemade battery charger, you must pay attention to the following requirements:

1. Providing a stable voltage of 14.4 V.
2. Device autonomy. This means that a homemade device should not require supervision, since the battery is often charged at night.
3. Ensuring that the charger turns off when the charging current or voltage increases.
4. Reverse polarity protection. If the device is connected to the battery incorrectly, the protection should be triggered. For implementation, a fuse is included in the circuit.

Polarity reversal is a dangerous process, as a result of which the battery may explode or boil. If the battery is in good condition and only slightly discharged, then if the charger is connected incorrectly, the charging current will increase above the rated one. If the battery is discharged, then when the polarity is reversed, an increase in voltage above the set value is observed and, as a result, the electrolyte boils.

Options for homemade battery chargers

Before you start developing a battery charger, it is important to understand that such a device is homemade and can negatively affect the battery life. However, sometimes such devices are simply necessary, as they can significantly save money on purchasing factory-made devices. Let's look at what you can make your own battery chargers from and how to do it.

Charging from a light bulb and a semiconductor diode

This charging method is relevant in situations where you need to start a car on a dead battery at home. In order to do this, you will need the components to assemble the device and a 220 V alternating voltage source (socket). The circuit of a homemade charger for a car battery contains the following elements:

1. Incandescent lamp. An ordinary light bulb, which is also popularly referred to as “Ilyich’s lamp.” The power of the lamp affects the charging speed of the battery, so the higher this indicator, the faster you can start the engine. The best option is a lamp with a power of 100-150 W.
2. Semiconductor diode. An electronic element whose main purpose is to conduct current in only one direction. The need for this element in the charging design is to convert alternating voltage to direct voltage. Moreover, for such purposes you will need a powerful diode that can withstand a heavy load. You can use a diode, either domestic or imported. In order not to buy such a diode, it can be found in old receivers or power supplies.
3. Plug for connecting to a socket.
4. Wires with terminals (crocodiles) for connecting to the battery.

It is important! Before assembling such a circuit, you need to understand that there is always a risk to life, so you should be extremely careful and careful.

Connection diagram of a charger from a light bulb and a diode to a battery

The plug should be plugged into the socket only after the entire circuit has been assembled and the contacts have been insulated. To avoid the occurrence of short circuit current, a 10 A circuit breaker is included in the circuit. When assembling the circuit, it is important to take into account the polarity. The light bulb and semiconductor diode must be connected to the positive terminal circuit of the battery. When using a 100 W light bulb, a charging current of 0.17 A will flow to the battery. To charge a 2 A battery, you will need to charge it for 10 hours. The higher the power of the incandescent lamp, the higher the charging current.

It makes no sense to charge a completely dead battery with such a device, but recharging it in the absence of a factory charger is quite possible.

Battery charger from rectifier

This option also falls into the category of the simplest homemade chargers. The basis of such a charger includes two main elements - a voltage converter and a rectifier. There are three types of rectifiers that charge the device in the following ways:

• D.C;
• alternating current;
• asymmetrical current.

Rectifiers of the first option charge the battery exclusively with direct current, which is cleared of alternating voltage ripples. AC rectifiers apply pulsating alternating voltage to the battery terminals. Asymmetric rectifiers have a positive component, and half-wave rectifiers are used as the main design elements. This circuit has better results compared to DC and AC rectifiers. It is its design that will be discussed further.

In order to assemble a high-quality battery charging device, you will need a rectifier and a current amplifier. The rectifier consists of the following elements:

• fuse;
• powerful diode;
• Zener diode 1N754A or D814A;
• switch;
• variable resistor.

Electrical circuit of an asymmetric rectifier

In order to assemble the circuit, you will need to use a fuse rated for a maximum current of 1 A. The transformer can be taken from an old TV, the power of which should not exceed 150 W, and the output voltage should be 21 V. As a resistor, you need to take a powerful element of the MLT- brand 2. The rectifier diode must be designed for a current of at least 5 A, so the best option is models like D305 or D243. The amplifier is based on a regulator based on two transistors of the KT825 and 818 series. During installation, the transistors are installed on radiators to improve cooling.

The assembly of such a circuit is carried out using a hinged method, that is, all the elements are located on the old board cleared of tracks and connected to each other using wires. Its advantage is the ability to adjust the output current for charging the battery. The disadvantage of the diagram is the need to find the necessary elements, as well as arrange them correctly.

The simplest analogue of the above diagram is a more simplified version, shown in the photo below.

Simplified circuit of a rectifier with a transformer

It is proposed to use a simplified circuit using a transformer and rectifier. In addition, you will need a 12 V and 40 W (car) light bulb. Assembling the circuit is not difficult even for a beginner, but it is important to pay attention to the fact that the rectifier diode and the light bulb must be located in the circuit that is fed to the negative terminal of the battery. The disadvantage of this scheme is that it produces a pulsating current. To smooth out pulsations, as well as reduce strong beats, it is recommended to use the circuit presented below.

A circuit with a diode bridge and a smoothing capacitor reduces ripple and reduces runout

Charger from a computer power supply: step-by-step instructions

Recently, a car charging option that you can make yourself using a computer power supply has become popular.

Initially you will need a working power supply. Even a unit with a power of 200 W is suitable for such purposes. It produces a voltage of 12 V. It will not be enough to charge the battery, so it is important to increase this value to 14.4 V. Step-by-step instructions for making a charger for a battery from a computer power supply are as follows:

1. Initially, all excess wires that come out of the power supply are soldered off. You only need to leave the green wire. Its end needs to be soldered to the negative contacts, where the black wires come from. This manipulation is done so that when the unit is connected to the network, the device starts up immediately.

   

   The end of the green wire must be soldered to the negative contacts where the black wires were located

2. The wires that will be connected to the battery terminals must be soldered to the minus and plus output contacts of the power supply. The plus is soldered to the exit point of the yellow wires, and the minus to the exit point of the black ones.
3. At the next stage, it is necessary to reconstruct the operating mode of pulse width modulation (PWM). The TL494 or TA7500 microcontroller is responsible for this. For reconstruction you will need the lower leftmost leg of the microcontroller. To get to it, you need to turn the board over.

   

   The TL494 microcontroller is responsible for the PWM operating mode.

4. Three resistors are connected to the bottom pin of the microcontroller. We are interested in the resistor that is connected to the output of the 12 V block. It is marked in the photo below with a dot. This element should be unsoldered, and then measure the resistance value.

   

   The resistor indicated by the purple dot must be desoldered

5. The resistor has a resistance of about 40 kOhm. It must be replaced with a resistor with a different resistance value. To clarify the value of the required resistance, you must first solder a regulator (variable resistor) to the contacts of the remote resistor.

   

   A regulator is soldered in place of the removed resistor

6. Now you should connect the device to the network, having previously connected a multimeter to the output terminals. The output voltage is changed using a regulator. You need to get a voltage value of 14.4 V.

   

   Output voltage is regulated by variable resistor

7. As soon as the voltage value is reached, the variable resistor should be unsoldered, and then the resulting resistance should be measured. For the example described above, its value is 120.8 kOhm.

   

   The resulting resistance should be 120.8 kOhm

8. Based on the obtained resistance value, you should select a similar resistor, and then solder it in place of the old one. If you cannot find a resistor of this resistance value, then you can select it from two elements.

   

   Soldering resistors in series adds up their resistance

9. After this, the functionality of the device is checked. If desired, you can install a voltmeter (or an ammeter) to the power supply, which will allow you to monitor the voltage and charging current.

General view of the charger from the computer power supply

This is interesting! The assembled charger has the function of protection against short circuit current, as well as against overload, but it does not protect against polarity reversal, so you should solder the output wires of the appropriate color (red and black) so as not to mix them up.

When connecting the charger to the battery terminals, a current of about 5-6 A will be supplied, which is the optimal value for devices with a capacity of 55-60 A/h. The video below shows how to make a charger for a battery from a computer power supply with voltage and current regulators.

What other charger options are there for batteries?

Let's consider several more options for independent battery chargers.

Using a laptop charger for the battery

One of the simplest and fastest ways to revive a dead battery. To implement the scheme for reviving the battery using charging from a laptop, you will need:

1. Charger for any laptop. The charger parameters are 19 V and the current is about 5 A.
2. Halogen lamp with a power of 90 W.
3. Connecting wires with clamps.

Let's move on to the implementation of the scheme. The light bulb is used to limit the current to an optimal value. You can use a resistor instead of a light bulb.

A laptop charger can also be used to “revive” a car battery.

Assembling such a scheme is not difficult. If you do not plan to use the laptop charger for its intended purpose, you can cut off the plug and then connect the clamps to the wires. First, use a multimeter to determine the polarity. The light bulb is connected to a circuit that goes to the positive terminal of the battery. The negative terminal from the battery is connected directly. Only after connecting the device to the battery can voltage be supplied to the power supply.

DIY charger from a microwave oven or similar devices

Using the transformer block, which is located inside the microwave, you can make a charger for the battery.

Step-by-step instructions for making a homemade charger from a transformer block from a microwave are presented below.

Connection diagram of a transformer block, diode bridge and capacitor to a car battery

The device can be assembled on any base. It is important that all structural elements are reliably protected. If necessary, the circuit can be supplemented with a switch, as well as a voltmeter.

Transformerless charger

If the search for a transformer has led to a dead end, then you can use the simplest circuit without step-down devices. Below is a diagram that allows you to implement a charger for a battery without using voltage transformers.

Electrical circuit of the charger without using a voltage transformer

The role of transformers is performed by capacitors, which are designed for a voltage of 250V. The circuit should include at least 4 capacitors, placing them in parallel. A resistor and an LED are connected in parallel to the capacitors. The role of the resistor is to dampen the residual voltage after disconnecting the device from the network.

The circuit also includes a diode bridge designed to operate with currents up to 6A. The bridge is included in the circuit after the capacitors, and the wires going to the battery for charging are connected to its terminals.

How to charge a battery from a homemade device

Separately, you should understand the question of how to properly charge the battery with a homemade charger. To do this, it is recommended to adhere to the following recommendations:

1. Maintain polarity. It is better to once again check the polarity of a homemade device with a multimeter rather than “biting your elbows”, because the cause of battery failure was an error with the wires.
2. Do not test the battery by shorting the contacts. This method only “kills” the device, and does not revive it, as indicated in many sources.
3. The device should be connected to a 220 V network only after the output terminals are connected to the battery. The device is turned off in the same way.
4. Compliance with safety precautions, since work is carried out not only with electricity, but also with battery acid.
5. The battery charging process must be monitored. The slightest malfunction can cause serious consequences.

Based on the above recommendations, it should be concluded that homemade devices, although acceptable, are still not capable of replacing factory ones. Making your own charger is not safe, especially if you are not confident that you can do it correctly. The material presents the simplest schemes for implementing chargers for car batteries, which will always be useful in the household.

The device with electronic control of the charging current is made on the basis of a thyristor phase-pulse power regulator. It does not contain rare radio components, and if the parts are known to work, it does not require adjustment. The charger allows you to charge the battery with a current from 0 to 10 amperes, and can also serve as an adjustable power source for a powerful low-voltage soldering iron, vulcanizer, portable lamp and just a power supply for all occasions.
The charging current is similar in shape to pulse current, which is believed to help extend battery life.
The device is operational at ambient temperatures from - 35 C to + 35 C.
The charger is a thyristor power regulator with phase-pulse control, powered from winding II of step-down transformer T1 through a diode bridge VDI...VD4.

All radio components of the device are domestic, but they can be replaced with similar foreign ones.
Capacitor C2 - K73-11, with a capacity of 0.47 to 1 μF, or K73-16, K73-17, K42U-2, MBGP.
We will replace the KT361A transistor with KT361B - KT361Ё, KT3107L, KT502V, KT502G, KT501Zh - KT50IK, and KT315L with KT315B + KT315D KT312B, KT3102L, KT503V + KT503G, P307. Instead of KD105B, diodes KD105V, KD105G or D226 with any letter index are suitable.
Variable resistor R1 - SP-1, SPZ-30a or SPO-1.
Ammeter PA1 - any direct current with a 10 ampere scale. You can make it yourself from any milliammeter by selecting a shunt based on a standard ammeter.
Fuse F1 is a fusible fuse, but it is convenient to use a 10-amp circuit breaker or a car bimetallic one for the same current.
Diodes VD1...VP4 can be any for a forward current of 10 amperes and a reverse voltage of at least 50 volts (series D242, D243, D245, KD203, KD210, KD213).
The rectifier diodes and thyristor are placed on aluminum radiators with a cooling area of ​​120 sq.cm. To improve the thermal contact of devices with radiators, be sure to lubricate heat-conducting pastes.
Thyristor KU202V will be replaced by KU202G - KU202E; It has been verified in practice that the device operates normally even with more powerful thyristors T-160, T-250.

The device uses a ready-made network step-down transformer of appropriate power with a secondary winding voltage of 18 to 22 volts.
If the transformer has a voltage on the secondary winding higher than 18 volts, it is advisable to replace resistor R5 with another one of the highest resistance (for example, at 24 - 26 volts, the resistor resistance should be increased to 200 Ohms).
In the case when the secondary winding of the transformer has a tap from the middle, or there are two identical windings and the voltage of each is within the specified limits, then it is better to design the rectifier according to the usual full-wave circuit with 2 diodes.
When the secondary winding voltage is 28 x 36 volts, you can completely abandon the rectifier - its role will simultaneously be played by the thyristor VS1 (rectification is half-wave). For this version of the power supply, you need to connect a separating diode KD105B or D226 with any letter index (cathode to resistor R5) between resistor R5 and the positive wire. The choice of thyristor in such a circuit will be limited - only those that allow operation under reverse voltage are suitable (for example, KU202E).
For the described device, a unified transformer TN-61 is suitable. Its 3 secondary windings must be connected in series, and they are capable of delivering current up to 8 amperes.

The device with electronic control of the charging current is made on the basis of a thyristor phase-pulse power regulator. It does not contain scarce parts, and if the elements are known to be good, it does not require adjustment.

This thyristor charger allows you to charge car batteries with a current from 0 to 10 A, and can also serve as a regulated power source for a powerful low-voltage soldering iron, vulcanizer, and portable lamp.

The charging current is similar in shape to pulse current, which is believed to help extend battery life. The device is operational at ambient temperatures from - 35 °C to + 35 °C. The device diagram is shown in Fig. 1.

Click on the picture to view.

The charger is a thyristor power regulator with phase-pulse control, powered from winding II of step-down transformer T1 through a diode bridge VD1 + VD4.

The thyristor control unit is made on an analogue of the unijunction transistor VT1, VT2. The time during which capacitor C2 is charged before switching the unijunction transistor can be adjusted with a variable resistor R1. When the engine is in the extreme right position according to the diagram, the charging current will be maximum, and vice versa.

Diode VD5 protects the control circuit of thyristor VS1 from reverse voltage that occurs when the thyristor is turned on.

The thyristor charger can later be supplemented with various automatic components (switching off at the end of charging, maintaining normal battery voltage during long-term storage, signaling the correct polarity of the battery connection, protection against output short circuits, etc.).

The disadvantages of the device include fluctuations in the charging current when the voltage of the electric lighting network is unstable.

Like all similar thyristor phase-pulse regulators, the device interferes with radio reception. To combat them, you should provide an LC network filter, similar to that used in switching network power supplies.

Capacitor C2 - K73-11, with a capacity of 0.47 to 1 µF, or. K73-16, K73-17, K42U-2, MBGP.

We will replace the KT361A transistor with KT361B - KT361Ё, KT3107L, KT502V, KT502G, KT501Zh - KT50IK, and KT315L with KT315B + KT315D KT312B, KT3102L, KT503V + KT503G, P307 Instead 05B suitable diodes KD105V, KD105G or. D226 with any letter index.

Variable resistor R1 - SP-1, SPZ-30a or SPO-1.

Ammeter PA1 - any direct current with a scale of 10 A. It can be made independently from any milliammeter by selecting a shunt based on a standard ammeter.

Fuse F1 is a fuse, but it is convenient to use a 10 A circuit breaker or a car bimetallic fuse for the same current.

Diodes VD1 + VP4 can be any for a forward current of 10 A and a reverse voltage of at least 50 V (series D242, D243, D245, KD203, KD210, KD213).

The rectifier diodes and thyristor are installed on heat sinks, each with a useful area of ​​​​about 100 cm 2. To improve the thermal contact of devices with heat sinks, it is advisable to use thermally conductive pastes.

Instead of a thyristor. KU202V will fit KU202G - KU202E; It has been verified in practice that the device works normally with more powerful thyristors T-160, T-250.

It should be noted that it is permissible to use the metal casing wall directly as a heat sink for the thyristor. Then, however, there will be a negative terminal of the device on the case, which is generally undesirable due to the danger of accidental short circuits of the positive output wire to the case. If you mount the thyristor through a mica gasket, there will be no danger of a short circuit, but the heat transfer from it will worsen.

The device can use a ready-made network step-down transformer of the required power with a secondary winding voltage of 18 to 22 V.

If the transformer has a voltage on the secondary winding of more than 18 V, resistor R5 should be replaced with another one of higher resistance (for example, at 24...26 V, the resistor resistance should be increased to 200 Ohms).

In the case when the secondary winding of the transformer is tapped from the middle, or there are two identical windings and the voltage of each is within the specified limits, then it is better to make the rectifier according to a standard full-wave circuit using two diodes.

When the secondary winding voltage is 28...36 V, you can completely abandon the rectifier - its role will simultaneously be played by thyristor VS1 (rectification is half-wave). For this version of the power supply, it is necessary to connect a separating diode KD105B or D226 with any letter index (cathode to resistor R5) between resistor R5 and the positive wire. The choice of thyristor in such a circuit will be limited - only those that allow operation under reverse voltage (for example, KU202E) are suitable.

For the described device, a unified transformer TN-61 is suitable. Its three secondary windings must be connected in series, and they are capable of delivering current up to 8 A.

All parts of the device, except for transformer T1, rectifier diodes VD1 - VD4, variable resistor R1, fuse FU1 and thyristor VS1, are mounted on a printed circuit board made of foil fiberglass 1.5 mm thick.

Very often, especially in the cold season, car enthusiasts are faced with the need to charge a car battery. It is possible, and advisable, to purchase a factory charger, preferably a charging and starting charger for use in the garage.

But, if you have electrical engineering skills and certain knowledge in the field of radio engineering, then you can make a simple charger for a car battery with your own hands. In addition, it is better to prepare in advance for the possible event that the battery suddenly discharges far from home or a place where it is parked and serviced.

General information about the battery charging process

Charging a car battery is necessary when the voltage drop across the terminals is less than 11.2 Volts. Despite the fact that the battery can start the car engine even with such a charge, during long-term parking at low voltages, plate sulfation processes begin, which lead to loss of battery capacity.

Therefore, when wintering a car in a parking lot or garage, it is necessary to constantly recharge the battery and monitor the voltage at its terminals. A better option is to remove the battery, put it in a warm place, but still do not forget about maintaining its charge.

The battery is charged using constant or pulsed current. In the case of charging from a constant voltage source, a charge current equal to one tenth of the battery capacity is usually selected.

For example, if the battery capacity is 60 Amp-hours, the charging current should be selected at 6 Amp. However, research shows that the lower the charge current, the less intense the sulfation processes.

Moreover, there are methods for desulfating battery plates. They are as follows. First, the battery is discharged to a voltage of 3 - 5 Volts with high currents of short duration. For example, such as when turning on the starter. Then there is a slow full charge with a current of about 1 Ampere. Such procedures are repeated 7-10 times. There is a desulfation effect from these actions.

Desulfating pulse chargers are practically based on this principle. The battery in such devices is charged with pulsed current. During the charging period (several milliseconds), a short discharge pulse of reverse polarity and a longer charging pulse of direct polarity are applied to the battery terminals.

It is very important during the charging process to prevent the effect of overcharging the battery, that is, the moment when it is charged to the maximum voltage (12.8 - 13.2 Volts, depending on the type of battery).

This can cause an increase in the density and concentration of the electrolyte, irreversible destruction of the plates. That is why factory chargers are equipped with an electronic control and shutdown system.

Schemes of homemade simple chargers for a car battery

Protozoa

Let's consider the case of how to charge a battery using improvised means. For example, a situation when you left your car near your house in the evening, forgetting to turn off some electrical equipment. By morning the battery was discharged and would not start the car.

In this case, if your car starts well (with half a turn), it is enough to “tighten” the battery a little. How to do it? First, you need a constant voltage source ranging from 12 to 25 volts. Secondly, restrictive resistance.

What can you recommend?

Nowadays, almost every home has a laptop. The power supply of a laptop or netbook, as a rule, has an output voltage of 19 Volts and a current of at least 2 amperes. The external pin of the power connector is minus, the internal pin is positive.

As a limiting resistance, and it is mandatory!!!, you can use the car's interior light bulb. You can, of course, have more power from turn signals or even worse stops or dimensions, but there is a possibility of overloading the power supply. The simplest circuit is assembled: minus the power supply - light bulb - minus the battery - plus the battery - plus the power supply. In a couple of hours the battery will be charged enough to start the engine.

If you don’t have a laptop, you can pre-purchase a powerful rectifier diode on the radio market with a reverse voltage of more than 1000 Volts and a current of 3 Amperes. It is small in size and can be put in the glove compartment for an emergency.

What to do in an emergency?

Conventional lamps can be used as a limiting load incandescent at 220 Volt. For example, a 100 Watt lamp (power = voltage X current). Thus, when using a 100-watt lamp, the charge current will be about 0.5 Ampere. Not much, but overnight it will give 5 Amp-hours of capacity to the battery. Usually it is enough to crank the car starter a couple of times in the morning.

If you connect three 100-watt lamps in parallel, the charging current will triple. You can charge your car battery almost halfway overnight. Sometimes they turn on an electric stove instead of lamps. But here the diode may already fail, and at the same time the battery.

In general, this kind of experiments with direct charging of the battery from an alternating voltage network of 220 Volts extremely dangerous. They should only be used in extreme cases when there is no other option.

From computer power supplies

Before you start making your own charger for a car battery, you should evaluate your knowledge and experience in the field of electrical and radio engineering. Accordingly, select the complexity level of the device.

First of all, you should decide on the element base. Very often, computer users are left with old system units. There are power supplies there. Along with the +5V supply voltage, they contain a +12 Volt bus. As a rule, it is designed for current up to 2 Amperes. This is quite enough for a weak charger.

Video - step-by-step manufacturing instructions and diagram of a simple charger for a car battery from a computer power supply:

But 12 volts is not enough. It is necessary to “overclock” it to 15. How? Usually using the “poke” method. Take a resistance of about 1 kiloOhm and connect it in parallel with other resistances near the microcircuit with 8 legs in the secondary circuit of the power supply.

Thus, the transmission coefficient of the feedback circuit changes, respectively, and the output voltage.

It’s difficult to explain in words, but usually users succeed. By selecting the resistance value, you can achieve an output voltage of about 13.5 Volts. This is enough to charge a car battery.

If you don’t have a power supply at hand, you can look for a transformer with a secondary winding of 12 - 18 Volts. They were used in old tube televisions and other household appliances.

Now such transformers can be found in used uninterruptible power supplies; they can be bought for pennies on the secondary market. Next, we begin manufacturing the transformer charger.

Transformer chargers

Transformer chargers are the most common and safe devices widely used in automotive practice.

Video - a simple charger for a car battery using a transformer:

The simplest circuit of a transformer charger for a car battery contains:

• network transformer;
• rectifier bridge;
• restrictive load.

A large current flows through the limiting load and it gets very hot, so to limit the charging current, capacitors are often used in the primary circuit of the transformer.

In principle, in such a circuit you can do without a transformer if you choose the capacitor wisely. But without galvanic isolation from the AC network, such a circuit will be dangerous from the point of view of electric shock.

More practical are charger circuits for car batteries with regulation and limitation of the charge current. One of these schemes is shown in the figure:

You can use the rectifier bridge of a faulty car generator as powerful rectifier diodes by slightly reconnecting the circuit.

More complex pulse chargers with desulfation function are usually made using microcircuits, even microprocessors. They are difficult to manufacture and require special installation and configuration skills. In this case, it is easier to purchase a factory device.

Safety requirements

Conditions that must be met when using a homemade car battery charger:

• The charger and battery must be located on a fireproof surface during charging;
• in the case of using simple chargers, it is necessary to use personal protective equipment (insulating gloves, rubber mat);
• when using newly manufactured devices, constant monitoring of the charging process is necessary;
• the main controlled parameters of the charging process are current, voltage at the battery terminals, temperature of the charger body and battery, control of the boiling point;
• When charging at night, it is necessary to have residual current devices (RCDs) in the network connection.

Video - diagram of a charger for a car battery from a UPS:

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Comments on the article:

Lyokha

The information presented here is certainly interesting and informative. As a former radio engineer of the Soviet school, I read it with great interest. But in reality, now even “desperate” radio amateurs are unlikely to bother searching for circuit diagrams for a homemade charger and later assembling it with a soldering iron and radio components. Only radio fanatics will do this. It’s much easier to buy a factory-made device, especially since the prices, I think, are affordable. As a last resort, you can turn to other car enthusiasts with a request to “light up”, fortunately, now there are plenty of cars everywhere. What is written here is useful not so much for its practical value (although that too), but for instilling interest in radio engineering in general. After all, most modern children not only cannot distinguish a resistor from a transistor, but they won’t be able to pronounce it the first time. And this is very sad...

Michael

When the battery was old and half-dead, I often used a laptop power supply to recharge. As a current limiter I used an unnecessary old taillight with four 21-watt bulbs connected in parallel. I control the voltage at the terminals, at the beginning of charging it is usually about 13 V, the battery greedily eats up the charge, then the charging voltage increases, and when it reaches 15 V, I stop charging. It takes half an hour to an hour to reliably start the engine.

Ignat

I have a Soviet charger in my garage, it’s called “Volna”, made in ’79. Inside is a hefty and heavy transformer and several diodes, resistors and transistors. Almost 40 years in service, and this despite the fact that my father and brother use it constantly, not only for charging, but also as a 12 V power supply. And now, indeed, it’s easier to buy a cheap Chinese device for five hundred square meters than to bother with soldering iron And on Aliexpress you can even buy it for one and a half hundred, but it will take a long time to send it. Although I liked the option from the computer power supply, I have a dozen old ones lying around in the garage, but they work quite well.

San Sanych

Hmmm. Of course, the Pepsicol generation is growing... :-\ The correct charger should produce 14.2 volts. No more and no less. With a greater potential difference, the electrolyte will boil, and the battery will swell so that it will then be problematic to remove it or, conversely, not to install it back in the car. With a smaller potential difference, the battery will not charge. The most normal circuit presented in the material is with a step-down transformer (first). In this case, the transformer must produce exactly 10 volts at a current of at least 2 amperes. There are plenty of these on sale. It is better to install domestic diodes - D246A (must be installed on a radiator with mica insulators). At worst - KD213A (these can be glued to an aluminum radiator with superglue). Any electrolytic capacitor with a capacity of at least 1000 uF for an operating voltage of at least 25 volts. A very large capacitor is also not needed, since due to the ripples of the under-rectified voltage we obtain the optimal charge for the battery. In total we get 10 * root of 2 = 14.2 volts. I myself have had such a charger since the days of the 412th Muscovite. Not killable at all. 🙂

Kirill

In principle, if you have the necessary transformer, it is not so difficult to assemble a transformer charger circuit yourself. Even for me, not a very big specialist in the field of radio electronics. Many people say, why bother if it’s easier to buy. I agree, but this is not about the final result, but about the process itself, because it is much more pleasant to use something made with your own hands than something purchased. And most importantly, if this homemade product breaks down, then the one who assembled it knows his battery charger thoroughly and is able to fix it quickly. And if a purchased product burns out, then you still need to dig around and it’s not at all a fact that a breakdown will be found. I vote for self-built devices!

Oleg

In general, I think that the ideal option is an industrial charger, so I have one and carry it in the trunk all the time. But in life situations are different. Once I was visiting my daughter in Montenegro, and there they generally don’t carry anything with them and rarely do anyone even have one. So she forgot to close the door at night. The battery is drained. No diode at hand, no computer. I found a Boschevsky screwdriver with 18 volts and 1 ampere current. So I used his charger. True, I charged it all night and periodically checked for overheating. But she couldn’t stand it, in the morning they started her with half a kick. So there are many options, you have to look. Well, regarding homemade chargers, as a radio engineer I can only recommend transformer ones, i.e. isolated via the network, they are safe compared to capacitors, diodes with a light bulb.

Sergey

Charging the battery with non-standard devices can lead to either complete irreversible wear or a decrease in guaranteed operation. The whole problem is connecting homemade products, no matter what the rated voltage exceeds the permissible one. It is necessary to take into account temperature changes and this is a very important point, especially in winter. When we decrease by a degree, we increase it and vice versa. There is an approximate table depending on the type of battery - it is not difficult to remember. Another important point is that all measurements of voltage and, of course, density are made only when the engine is cold, with the engine not running.

Vitalik

In general, I use the charger extremely rarely, maybe once every two or three years, and only when I go away for a long time, for example in the summer for a couple of months to the south to visit relatives. And so basically the car is in operation almost every day, the battery is charged and there is no need for such devices. Therefore, I think that buying for money something that you practically never use is not very smart. The best option is to assemble such a simple craft, say from a computer power supply, and let it lie around, waiting in the wings. After all, the main thing here is not to fully charge the battery, but to cheer it up a little to start the engine, and then the generator will do its job.

Nikolay

Just yesterday we recharged the battery using a screwdriver charger. The car was parked outside, the frost was -28, the battery was spun a couple of times and stopped. We took out a screwdriver, a couple of wires, connected it, and after half an hour the car started up safely.

Dmitriy

A ready-made store charger is of course an ideal option, but who wants to use their own hands, and considering that you don’t have to use it often, you don’t have to spend money on the purchase and do the charging yourself.
A homemade charger should be autonomous, not require supervision or current control, since we charge most often at night. In addition, it must provide a voltage of 14.4 V and ensure that the battery is turned off when the current and voltage exceed the norm. It should also provide protection against polarity reversal.
The main mistakes that “Kulibins” make is connecting directly to a household electrical network, this is not even a mistake, but a violation of safety regulations, the next limiting the charging current is by capacitors, and it’s also more expensive: one bank of capacitors 32 uF at 350-400 V (less than that is not possible) will cost like a cool branded charger.
The easiest way is to use a computer switching power supply (UPS), it is now more affordable than a hardware transformer, and you don’t need to do separate protection, everything is ready.
If you don't have a computer power supply, you need to look for a transformer. A power supply with filament windings from old tube TVs - TS-130, TS-180, TS-220, TS-270 - is suitable. They have plenty of power behind their eyes. You can find an old TN filament transformer at the car market.
But all this is only for those who are friends with electricians. If not, don’t bother - you won’t do the exercises that meet all the requirements, so buy ready-made ones and don’t waste time.

Laura

I got a charger from my grandfather. Since Soviet times. Homemade. I don’t understand this at all, but when my friends see it, they click their tongues in admiration and respect, saying, this is a thing “for centuries.” They say it was assembled using some lamps and still works. True, I practically don’t use it, but that’s not the point. Everyone criticizes Soviet technology, but it turns out to be many times more reliable than modern technology, even homemade ones.

Vladislav

In general, a useful thing in the household, especially if there is a function for adjusting the output voltage

Alexei

I’ve never had the opportunity to use or assemble homemade chargers, but I can quite imagine the principle of assembly and operation. I think that homemade products are no worse than factory ones, it’s just that no one wants to tinker, especially since the prices for store-bought ones are quite affordable.

Victor

In general, the schemes are simple, there are few parts and they are accessible. Adjustment can also be done if you have some experience. So it's quite possible to collect. Of course, it is very pleasant to use a device assembled with your own hands)).

Ivan

The charger is, of course, a useful thing, but now there are more interesting specimens on the market - their name is start-chargers

Sergey

There are a lot of charger circuits and as a radio engineer I have tried many of them. Until last year, I had a scheme that worked for me since Soviet times and it worked perfectly. But one day (through my fault) the battery completely died in the garage and I needed a cyclic mode to restore it. Then I didn’t bother (due to lack of time) with creating a new circuit, but just went and bought it. And now I carry a charger in the trunk just in case.

Car owners often face a problem battery discharge. If this happens far from service stations, auto shops and gas stations, you can independently make a device for charging the battery from available parts. Let's look at how to make a charger for a car battery with your own hands, having minimal knowledge of electrical installation work.

This device is best used only in critical situations. However, if you are familiar with electrical engineering, electrical and fire safety rules, and have skills in electrical measurements and installation work, a homemade charger can easily replace the factory unit.

Causes and signs of battery discharge

During the operation of the battery, when the engine is running, the battery is constantly recharged from the vehicle's generator. You can check the charging process by connecting a multimeter to the battery terminals with the engine running, measuring the charging voltage of the car battery. The charge is considered normal if the voltage at the terminals is from 13.5 to 14.5 Volts.

To fully charge, you need to drive the car for at least 30 kilometers, or about half an hour in city traffic.

The voltage of a normally charged battery during parking should be at least 12.5 Volts. If the voltage is less than 11.5 Volts, the car engine may not start during the start. Reasons for battery discharge:

• The battery has significant wear ( more than 5 years of operation);
• improper operation of the battery, leading to sulfation of the plates;
• long-term parking of the vehicle, especially in the cold season;
• urban rhythm of car driving with frequent stops when the battery does not have time to charge sufficiently;
• leaving the car's electrical appliances on while parked;
• damage to the electrical wiring and equipment of the vehicle;
• leaks in electrical circuits.

Many car owners do not have the means to measure battery voltage in their on-board tool kit ( voltmeter, multimeter, probe, scanner). In this case, you can be guided by indirect signs of battery discharge:

• dim lights on the dashboard when the ignition is turned on;
• lack of starter rotation when starting the engine;
• loud clicks in the starter area, lights on the dashboard going out when starting;
• complete lack of reaction from the car when the ignition is turned on.

If the listed symptoms appear, first of all you need to check the battery terminals, if necessary, clean and tighten them. In the cold season, you can try to bring the battery into a warm room for a while and warm it up.

You can try to “light” the car from another car. If these methods do not help or are not possible, you have to use a charger.

DIY universal charger. Video:

Operating principle

Most devices charge batteries with constant or pulsed currents. How many amps does it take to charge a car battery? The charge current is chosen equal to one tenth of the battery capacity. With a capacity of 100 Ah, the charging current of a car battery will be 10 Amperes. The battery will have to be charged for about 10 hours until it is fully charged.

Charging a car battery with high currents can lead to the sulfation process. To avoid this, it is better to charge the battery with low currents, but for a longer time.

Pulse devices significantly reduce the effect of sulfation. Some pulse chargers have a desulfation mode, which allows you to restore battery functionality. It consists of sequential charge-discharge with pulsed currents according to a special algorithm.

When charging the battery, do not allow it to overcharge. It can lead to boiling of the electrolyte and sulfation of the plates. It is necessary that the device has its own control system, parameter measurement and emergency shutdown.

Since the 2000s, special types of batteries began to be installed on cars: AGM and gel. Charging a car battery of these types differs from the normal mode.

As a rule, it is three-stage. Up to a certain level, the charge occurs with a large current. Then the current decreases. The final charge occurs with even smaller pulse currents.

Charging a car battery at home

Often in driving practice a situation arises when, having parked the car near the house in the evening, in the morning it is discovered that the battery is discharged. What can be done in such a situation when there is no soldering iron at hand, no parts, but you need to start it?

Usually the battery has a small capacity left; it just needs to be “tightened up” a little so that there is enough charge to start the engine. In this case, a power supply from some household or office equipment, for example, a laptop, can help.

Charging from a laptop power supply

The voltage produced by the laptop power supply is usually 19 Volts, the current is up to 10 Amps. This is enough to charge the battery. But you CANNOT connect the power supply directly to the battery. It is necessary to include a limiting resistance in series in the charging circuit. You can use a car light bulb as it, better for interior lighting. It can be purchased at your nearest gas station.

Typically the middle pin of the connector is positive. A light bulb is connected to it. The + battery is connected to the second terminal of the light bulb.

The negative terminal is connected to the negative terminal of the power supply. The power supply usually has a label indicating the polarity of the connector. A couple of hours of charging using this method is enough to start the engine.

Circuit diagram of a simple charger for a car battery.

Charge from a household network

A more extreme charging method is directly from a household outlet. It is used only in a critical situation, using maximum electrical safety measures. To do this you will need a lighting lamp ( not energy saving).

You can use an electric stove instead. You also need to purchase a rectifier diode. Such a diode can be “borrowed” from a faulty energy-saving lamp. During this time, it is better to turn off the voltage supplied to the apartment. The diagram is shown in the figure.

The charging current with a lamp power of 100 Watts will be approximately 0.5 A. Overnight the battery will be recharged for only a few ampere-hours, but this may be enough to start. If you connect three lamps in parallel, the battery will be charged three times more. If you connect an electric stove instead of a light bulb ( at the lowest power), then the charging time will be significantly reduced, but this is very dangerous. In addition, the diode may break through, then the battery may short out. Charging methods from 220 V are dangerous.

DIY car battery charger. Video:

Homemade car battery charger

Before making a charger for a car battery, you should evaluate your experience in electrical installation work and knowledge of electrical engineering, and based on this, proceed to choosing a charger circuit for a car battery.

You can look in the garage to see if there are old devices or units. A power supply from an old computer is suitable for the device. It has almost everything:

• 220 V connector;
• power switch;
• electrical circuit;
• cooling Fan;
• connection terminals.

The voltages on it are standard: +5 V, -12 V and +12 Volts. To charge the battery, it is better to use a +12 Volt, 2 Ampere wire. The output voltage must be raised to the level of +14.5 - +15.0 Volts. This can usually be done by changing the resistance value in the feedback circuit ( about 1 kiloohm).

There is no need to install a limiting resistance; the electronic circuit will independently regulate the charge current within 2 Amperes. It is easy to calculate that it will take about a day to fully charge a 50 A*h battery. Appearance of the device.

You can pick up or buy at a flea market a network transformer with a secondary winding voltage from 15 to 30 Volts. These were used in old TVs.

Transformer devices

The simplest circuit diagram of a device with a transformer.

Its disadvantage is the need to limit the current in the output circuit and the associated large power losses and heating of the resistors. Therefore, capacitors are used to regulate the current.

Theoretically, having calculated the value of the capacitor, you can not use a power transformer, as shown in the diagram.

When purchasing capacitors, you should choose the appropriate rating with a voltage of 400 V or more.

In practice, devices with current regulation have become more widely used.

You can choose pulse homemade charger circuits for a car battery. They are more complex in circuit design and require certain installation skills. Therefore, if you do not have special skills, it is better to buy a factory unit.

Pulse chargers

Pulse chargers have a number of advantages:

The operating principle of pulse devices is based on converting alternating voltage from a household electrical network into direct voltage using a VD8 diode assembly. The DC voltage is then converted into pulses of high frequency and amplitude. Pulse transformer T1 again converts the signal into DC voltage, which charges the battery.

Since the reverse conversion is carried out at a high frequency, the dimensions of the transformer are much smaller. The feedback necessary to control the charge parameters is provided by optocoupler U1.

Despite the apparent complexity of the device, when assembled correctly the unit begins to work without additional adjustment. This device provides a charging current of up to 10 Amps.

When charging the battery using a homemade device, you must:

• place the device and battery on a non-conductive surface;
• comply with electrical safety requirements ( use gloves, a rubber mat, and tools with an electrical insulating coating);
• Do not leave the charger turned on for a long time without control, monitor the voltage and temperature of the battery, and the charging current.