DIY charger circuits for car batteries. How to make a charger for a car battery from a transformer

30.06.2023

Battery problems are not that uncommon. To restore functionality, additional charging is necessary, but normal charging costs a lot of money, and it can be done from available “trash.” The most important thing is to find a transformer with the required characteristics, and making a charger for a car battery with your own hands takes just a couple of hours (if you have all the necessary parts).

The battery charging process must follow certain rules. Moreover, the charging process depends on the type of battery. Violations of these rules lead to a decrease in capacity and service life. Therefore, the parameters of a car battery charger are selected for each specific case. This opportunity is provided by a complex charger with adjustable parameters or purchased specifically for this battery. There is a more practical option - making a charger for a car battery with your own hands. To know what parameters should be, a little theory.

Types of battery chargers

Battery charging is the process of restoring used capacity. To do this, a voltage is supplied to the battery terminals that is slightly higher than the operating parameters of the battery. Can be served:

D.C. The charging time is at least 10 hours, during this entire time a fixed current is supplied, the voltage varies from 13.8-14.4 V at the beginning of the process to 12.8 V at the very end. With this type, the charge accumulates gradually and lasts longer. The disadvantage of this method is that it is necessary to control the process and turn off the charger in time, since when overcharging the electrolyte may boil, which will significantly reduce its working life.
Constant pressure. When charging with a constant voltage, the charger produces a voltage of 14.4 V all the time, and the current varies from large values in the first hours of charging to very small values in the last. Therefore, the battery will not be recharged (unless you leave it for several days). The positive aspect of this method is that the charging time is reduced (90-95% can be reached in 7-8 hours) and the battery being charged can be left unattended. But such an “emergency” charge recovery mode has a bad effect on service life. With frequent use of constant voltage, the battery discharges faster.

In general, if there is no need to rush, it is better to use DC charging. If you need to restore battery functionality in a short time, apply constant voltage. If we talk about what is the best charger to make for a car battery with your own hands, the answer is clear - one that supplies direct current. The schemes will be simple, consisting of accessible elements.

How to determine the necessary parameters when charging with direct current

It has been experimentally established that charge car lead acid batteries(most of them) required current that does not exceed 10% of the battery capacity. If the capacity of the battery being charged is 55 A/h, the maximum charge current will be 5.5 A; with a capacity of 70 A/h - 7 A, etc. In this case, you can set a slightly lower current. The charge will continue, but more slowly. It will accumulate even if the charge current is 0.1 A. It will just take a very long time to restore the capacity.

Since the calculations assume that the charge current is 10%, we obtain a minimum charge time of 10 hours. But this is when the battery is completely discharged, and this should not be allowed. Therefore, the actual charging time depends on the “depth” of the discharge. You can determine the depth of discharge by measuring the voltage on the battery before charging:

To calculate approximate battery charging time, you need to find out the difference between the maximum battery charge (12.8 V) and its current voltage. Multiplying the number by 10 we get the time in hours. For example, the voltage on the battery before charging is 11.9 V. We find the difference: 12.8 V - 11.9 V = 0.8 V. Multiplying this figure by 10, we find that the charging time will be about 8 hours. This is provided that we supply a current that is 10% of the battery capacity.

Charger circuits for car batteries

To charge batteries, a 220 V household network is usually used, which is converted to reduced voltage using a converter.

Simple circuits

The simplest and most effective way is to use a step-down transformer. It is he who lowers 220 V to the required 13-15 V. Such transformers can be found in old tube TVs (TS-180-2), computer power supplies, and found at flea market “ruins”.

But the output of the transformer produces an alternating voltage that must be rectified. They do this using:

The above diagrams also contain fuses (1 A) and measuring instruments. They make it possible to control the charging process. They can be excluded from the circuit, but you will have to periodically use a multimeter to monitor them. With voltage control this is still tolerable (just attach probes to the terminals), but it is difficult to control the current - in this mode the measuring device is connected to an open circuit. That is, you will have to turn off the power every time, put the multimeter in current measurement mode, and turn on the power. disassemble the measuring circuit in reverse order. Therefore, using at least a 10 A ammeter is very desirable.

The disadvantages of these schemes are obvious - there is no way to adjust the charging parameters. That is, when choosing an element base, choose the parameters so that the output current is the same 10% of the capacity of your battery (or a little less). You know the voltage - preferably within 13.2-14.4 V. What to do if the current turns out to be more than desired? Add a resistor to the circuit. It is placed at the positive output of the diode bridge in front of the ammeter. You select the resistance “locally”, focusing on the current; the power of the resistor is larger, since excess charge will be dissipated on them (10-20 W or so).

And one more thing: a do-it-yourself car battery charger made according to these schemes will most likely get very hot. Therefore, it is advisable to add a cooler. It can be inserted into the circuit after the diode bridge.

Adjustable circuits

As already mentioned, the disadvantage of all these circuits is the inability to regulate the current. The only option is to change the resistance. By the way, you can put a variable tuning resistor here. This will be the easiest way out. But manual current adjustment is more reliably implemented in a circuit with two transistors and a trimming resistor.

The charging current is changed by a variable resistor. It is located after the composite transistor VT1-VT2, so a small current flows through it. Therefore, the power can be about 0.5-1 W. Its rating depends on the selected transistors and is selected experimentally (1-4.7 kOhm).

Transformer with a power of 250-500 W, secondary winding 15-17 V. The diode bridge is assembled on diodes with an operating current of 5A and higher.

Transistor VT1 - P210, VT2 is selected from several options: germanium P13 - P17; silicon KT814, KT 816. To remove heat, install on a metal plate or radiator (at least 300 cm2).

Fuses: at the input PR1 - 1 A, at the output PR2 - 5 A. Also in the circuit there are signal lamps - the presence of a voltage of 220 V (HI1) and a charging current (HI2). Here you can install any 24 V lamps (including LEDs).

Video on the topic

DIY car battery charger is a popular topic for car enthusiasts. Transformers are taken from everywhere - from power supplies, microwave ovens... they even wind them themselves. The schemes being implemented are not the most complex. So even without electrical engineering skills you can do it yourself.

The article will tell you how to make a homemade one with your own hands. You can use absolutely any circuits, but the simplest manufacturing option is to remake a computer power supply. If you have such a block, it will be quite easy to find a use for it. To power motherboards, voltages of 5, 3.3, 12 Volts are used. As you understand, the voltage of interest to you is 12 Volts. The charger will allow you to charge batteries whose capacity ranges from 55 to 65 Ampere-hours. In other words, it is enough to recharge the batteries of most cars.

General view of the diagram

To make the alteration, you need to use the diagram presented in the article. made with your own hands from the power supply of a personal computer, allows you to control the charging current and voltage at the output. It is necessary to pay attention to the fact that there is protection against short circuit - a 10 Ampere fuse. But it is not necessary to install it, since most power supplies of personal computers have protection that turns off the device in the event of a short circuit. Therefore, charger circuits for batteries from computer power supplies are able to protect themselves from short circuits.

The PSI controller (designated DA1), as a rule, is used in the power supply of two types - KA7500 or TL494. Now a little theory. Can the computer's power supply charge the battery normally? The answer is yes, since lead batteries in 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 over 150 W, then its “+12 V” circuit is capable of delivering such current.

Initial stage of remodeling

To replicate a simple homemade battery charger, you need to slightly improve the power supply:

Get rid of all unnecessary wires. Use a soldering iron to remove them so as not to interfere.
Using the diagram given in the article, find a constant resistor R1, which must be unsoldered and in its place install a trimmer with a resistance of 27 kOhm. A constant voltage of “+12 V” must subsequently be applied to the upper contact of this resistor. Without this, the device will not be able to operate.
The 16th pin of the microcircuit is disconnected from the minus.
Next, you need to disconnect the 15th and 14th pins.

It turns out to be quite simple and homemade. You can use any circuits, but it’s easier to make it from a computer power supply - it’s lighter, easier to use, and more affordable. When compared with transformer devices, the mass of the devices differs significantly (as do the dimensions).

Charger adjustments

The back wall will now be the front; it is advisable 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-sensing resistor as powerful as possible - take two with a power of 5 W and a resistance of 0.2 Ohm. But it all depends on the choice of battery charger circuit. Some designs do not require the use of high-power resistors.

When connecting them in parallel, the power is doubled, and the resistance becomes equal to 0.1 Ohm. On the front wall there are also indicators - a voltmeter and an ammeter, which allow you to monitor the relevant parameters of the charger. To fine-tune the charger, a trimming resistor is used, with which voltage is supplied to the 1st pin of the PHI controller.

Device requirements

Final assembly

Multi-core 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 car charger will fail. After assembly, you need to set the voltage to about 14 Volts (+/-0.2 V) using a trimmer resistor. This is the voltage that is considered normal for charging batteries. Moreover, this value should be in idle mode (without a connected load).

You must install two alligator clips on the wires that connect to the battery. One is red, the other is black. These can be purchased at any hardware or auto parts store. This is how you get a simple homemade charger for a car battery. Connection diagrams: black is attached to the minus, and red to the plus. The charging process is completely automatic, no human intervention is required. But it is worth considering the main stages of this process.

Battery charging process

During the initial cycle, the voltmeter will show a voltage of approximately 12.4-12.5 V. If the battery has a capacity of 55 Ah, then you need to rotate the regulator until the ammeter shows a value of 5.5 Amperes. This means that the charging current is 5.5 A. As the battery charges, the current decreases and the voltage tends to a maximum. As a result, at the very end the current will be 0 and the voltage will be 14 V.

Regardless of the selection of circuits and designs of chargers used for manufacturing, the operating principle is largely similar. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not risk the battery overcharging. Therefore, the charger can be connected to the battery for a day, a week, or even a month.

If you don’t have measuring instruments that you wouldn’t 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 of 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 battery charger, made with your own hands without the use of equipment, can be easily used.

This is a very simple attachment circuit for your existing charger. Which will control the battery charge voltage and, when the set level is reached, disconnect it from the charger, thereby preventing the battery from overcharging.
This device has absolutely no scarce parts. The entire circuit is built on just one transistor. It has LED indicators that indicate the status: charging in progress or the battery is charged.

Who will benefit from this device?

This device will definitely come in handy for motorists. For those who do not have an automatic charger. This device will turn your regular charger into a fully automatic charger. You no longer have to constantly monitor the charging of your battery. All you need to do is put the battery on charge, and it will turn off automatically only after it is fully charged.

Automatic charger circuit

Here is the actual circuit diagram of the machine. In fact, it is a threshold relay that is activated when a certain voltage is exceeded. The response threshold is set by variable resistor R2. For a fully charged car battery, it is usually equal to - 14.4 V.
You can download the diagram here -

Printed circuit board

How to make a printed circuit board is up to you. It is not complicated and therefore can easily be laid out on a breadboard. Well, or you can get confused and make it on textolite with etching.

Settings

If all the parts are in good working order, setting up the machine is reduced only to setting the threshold voltage with resistor R2. To do this, we connect the circuit to the charger, but do not connect the battery yet. We move resistor R2 to the lowest position according to the diagram. We set the output voltage on the charger to 14.4 V. Then slowly rotate the variable resistor until the relay operates. Everything is set.
Let's play with the voltage to make sure that the console works reliably at 14.4 V. After this, your automatic charger is ready for use.
In this video you can watch in detail the process of all assembly, adjustment and testing in operation.

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:

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.
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 into charging 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:

Providing a stable voltage of 14.4 V.
Device autonomy. This means that a homemade device should not require supervision, since the battery is often charged at night.
Ensuring that the charger turns off when the charging current or voltage increases.
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 the purchase of factory 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:

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.
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.
Plug for connecting to a socket.
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 AC voltage to the battery terminals. Asymmetric rectifiers have a positive component, and half-wave rectifiers are used as the main design elements. This scheme 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:

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
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.
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
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
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
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
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
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
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 a few 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:

Charger for any laptop. The charger parameters are 19 V and the current is about 5 A.
Halogen lamp with a power of 90 W.
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 circuit 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:

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.
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.
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.
Compliance with safety precautions, since work is carried out not only with electricity, but also with battery acid.
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.

Under normal operating conditions, the vehicle's electrical system is self-sufficient. We are talking about energy supply - a combination of a generator, a voltage regulator, and a battery works synchronously and ensures uninterrupted power supply to all systems.

This is in theory. In practice, car owners make amendments to this harmonious system. Or the equipment refuses to work in accordance with the established parameters.

For example:

Operating a battery that has exhausted its service life. The battery does not hold a charge
Irregular trips. Prolonged downtime of the car (especially during hibernation) leads to self-discharge of the battery
The car is used for short trips, with frequent stopping and starting of the engine. The battery simply does not have time to recharge
Connecting additional equipment increases the load on the battery. Often leads to increased self-discharge current when the engine is turned off
Extremely low temperature accelerates self-discharge
A faulty fuel system leads to increased load: the car does not start immediately, you have to turn the starter for a long time
A faulty generator or voltage regulator prevents the battery from charging properly. This problem includes worn power wires and poor contact in the charging circuit.
And finally, you forgot to turn off the headlights, lights or music in the car. To completely discharge the battery overnight in the garage, sometimes it is enough to close the door loosely. Interior lighting consumes quite a lot of energy.

Any of the following reasons leads to an unpleasant situation: you need to drive, but the battery is unable to crank the starter. The problem is solved by external recharge: that is, a charger.

The tab contains four proven and reliable car charger circuits from simple to the most complex. Choose any one and it will work.

A simple 12V charger circuit.

Charger with adjustable charging current.

Adjustment from 0 to 10A is carried out by changing the opening delay of the SCR.