How to make a battery charger. How to make a charger for a car battery from a transformer

Every motorist has experienced a moment in life when, after turning the key in the ignition, absolutely nothing happened. The starter would not turn, and as a result, the car would not start. The diagnosis is simple and clear: the battery is completely discharged. But having even the simplest one with an output voltage of 12 V on hand, you can restore the battery within one hour and go about your business. How to make such a device with your own hands is described later in the article.

How to properly charge a battery

Before you make a battery charger with your own hands, you should learn the basic rules regarding how to properly charge it. If you do not follow them, the battery life will sharply decrease and you will have to buy a new one, since it is almost impossible to restore the battery.

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

Now we need to deal with the tension. For batteries whose potential difference is 12 V, the charging voltage should not exceed 16.2 V. This means that for one bank the voltage should be within 2.7 V.

The most basic rule for proper battery charging: do not mix up the terminals when connecting the battery. Incorrectly connected terminals are called polarity reversal, which will lead to immediate boiling of the electrolyte and final failure of the battery.

Required tools and supplies

You can make a high-quality charger with your own hands only if you have prepared tools and consumables under your hands.

List of tools and consumables:

• Multimeter. It should be in every motorist's tool bag. It will be useful not only when assembling the charger, but also in the future during repairs. A standard multimeter includes functions such as measuring voltage, current, resistance and continuity of conductors.
• Soldering iron. A power of 40 or 60 W is sufficient. You cannot use a soldering iron that is too powerful, as high temperatures will lead to damage to dielectrics, for example, in capacitors.
• Rosin. Necessary for a rapid increase in temperature. If the parts are not heated sufficiently, the soldering quality will be too low.
• Tin. The main fastening material is used to improve the contact of two parts.
• Heat-shrink tubing. A newer version of the old electrical tape, it is easy to use and has better dielectric properties.

Of course, tools such as pliers, a flat-head and shaped screwdriver should always be at hand. Having collected all the above elements, you can begin assembling the battery charger.

Sequence of manufacturing charging based on a switching power supply

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

Ready charging based on a switching power supply

What you will need:

• Electronic type transformer from the Chinese manufacturer Tashibra.
• Dinistor KN102. The foreign dinistor is marked DB3.
• Power keys MJE13007 in the amount of two pieces.
• Four KD213 diodes.
• A resistor with a resistance of at least 10 Ohms and a power of 10 W. If you install a lower power resistor, it will constantly heat up and very soon fail.
• Any feedback transformer that can be found in old radios.

You can place the circuit on any old board or buy a plate of inexpensive dielectric material for this. After assembling the circuit, it will need to be hidden in a metal case, which can be made from simple tin. The circuit must be isolated from the housing.

An example of a charger mounted in the case of an old system unit

The sequence of making a charger with your own hands:

• Remake the power transformer. To do this, you need to unwind its secondary winding, since Tashibra pulse transformers provide only 12 V, which is very little for a car battery. In place of the old winding, 16 turns of a new double wire should be wound, the cross-section of which will not be less than 0.85 mm. The new winding is insulated, and the next one is wound on top of it. Only now you need to make only 3 turns, the wire cross-section is at least 0.7 mm.
• Install short circuit protection. To do this you will need the same 10 ohm resistor. It should be soldered into the gap in the windings of the power transformer and the feedback transformer.

Resistor as short circuit protection

• Using four KD213 diodes, solder the rectifier. The diode bridge is simple, can operate with high frequency current, and is manufactured according to a standard design.

Diode bridge based on KD213A

• Making a PWM controller. Necessary in a charger, as it controls all power switches in the circuit. You can make it yourself using a field-effect transistor (for example, IRFZ44) and reverse conduction transistors. Elements of type KT3102 are ideal for these purposes.

PWM=high quality controller

• Connect the main circuit with the power transformer and the PWM controller. After which the resulting assembly can be secured in a self-made housing.

This charger is quite simple, does not require large expenses for assembly, and is lightweight. But circuits made on the basis of pulse transformers cannot be classified as reliable. Even the simplest standard power transformer will produce more stable performance than pulsed devices.

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

Simple DIY charger

To make this charger, you will need elements that can be found in a used old-type TV. Before installing them in a new circuit, the parts must be checked with a multimeter.

The main part of the circuit is the power transformer, which cannot be found everywhere. Its marking: TS-180-2. A transformer of this type has 2 windings, the voltage of which is 6.4 and 4.7 V. To obtain the required potential difference, these windings should be connected in series - the output of the first should be connected to the input of the second by soldering or an ordinary terminal block.

Transformer type TS-180-2

You will also need four D242A type diodes. Since these elements will be assembled in a bridge circuit, excess heat will need to be removed from them during operation. Therefore, it is also necessary to find or purchase 4 cooling radiators for radio components with an area of ​​at least 25 mm2.

All that remains is the base, for which you can take a fiberglass plate and 2 fuses, 0.5 and 10A. Conductors can be used of any cross-section, only the input cable must be at least 2.5 mm2.

Charger assembly sequence:

1. The first element in the circuit is to assemble a diode bridge. It is assembled according to the standard scheme. The terminal locations should be lowered down, and all diodes should be placed on cooling radiators.
2. From the transformer, from terminals 10 and 10′, draw 2 wires to the input of the diode bridge. Now you need to slightly modify the primary windings of the transformers, and to do this, solder a jumper between pins 1 and 1′.
3. Solder the input wires to pins 2 and 2′. The input wire can be made from any cable, for example, from any used household appliance. If only a wire is available, then you need to attach a plug to it.
4. A fuse rated at 0.5A should be installed in the gap in the wire leading to the transformer. In the positive gap, which will go directly to the battery terminal, there is a 10A fuse.
5. The negative wire coming from the diode bridge is soldered in series to an ordinary lamp rated at 12 V, with a power of no more than 60 W. This will help not only control battery charging, but also limit the charging current.

All elements of this charger can be placed in a tin case, also made by hand. Fix the fiberglass plate with bolts, and mount the transformer directly on the housing, having previously placed the same fiberglass plate between it and the sheet metal.

Ignoring the laws of electrical engineering can lead to the charger constantly failing. Therefore, it is worth planning the charging power in advance, depending on which to assemble the circuit. If you exceed the power of the circuit, then the battery will not be properly charged unless the operating voltage is exceeded.

Probably every motorist is familiar with the problem of a dead or completely failed battery. Of course, resuscitating a car is not so difficult, but what if there is absolutely no time and you need to go urgently? After all, not everyone has a charger. From this material you will learn how to make a charger for a car battery with your own hands, what types there are.

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Pulse chargers for batteries

Not so long ago, transformer-type chargers were found everywhere, but today finding such a charger will be quite problematic. Over time, transformers faded into the background, losing ground. Unlike a transformer, a pulse charger allows you to provide full power, but this advantage is not the main one.

Working with a transformer required some skill, but with pulse memory devices they are quite easy to operate. In addition, unlike transformers, their cost is more affordable. Also, the transformer is characterized by large dimensions, and the dimensions of the pulse devices are more compact.

The battery of a pulse device, unlike a transformer, is charged in two stages. The first is constant voltage, the second is constant current. Usually, modern memory devices are based on similar, but quite complex circuits. So, if this device fails, the motorist will most likely have to buy a new one.

As for lead-acid batteries, these batteries are, in principle, temperature sensitive. If it’s hot outside, then the charge level should be at least half, and if the temperature is sub-zero, then the battery should be charged at least 75%. Otherwise, the charger will simply stop functioning and will need to be recharged. 12-volt pulse chargers are excellent for such purposes, since they do not have a negative impact on the battery itself (video author: Artem Petukhov).

Automatic chargers for car batteries

If you are a novice motorist, then it would be better for you to use an automatic battery charger. These chargers are equipped with rich functionality and protective options, which allows you to warn the driver if the connection is incorrect. In addition, the automatic charger will prevent voltage from being applied if it is not connected correctly. Sometimes charging can independently calculate the charge level and battery capacity.

Automatic memory circuits are equipped with additional devices - timers, which allow you to perform several different tasks. We are talking about fully charging the battery, rapid charging, as well as full. When the task is completed, the charger will notify the motorist about this and will automatically turn off.

As you know, if the precautions for using batteries are not followed, sulfitation, that is, salts, can occur on the battery plates. Thanks to the charge-discharge cycle, you can not only remove salts, but also increase the service life of the battery as a whole. In general, the cost of modern 12-volt chargers is not particularly high, so every motorist can purchase such a device. But there are times when the device is needed right now, but there is no way to charge the battery. You can try to make a simple homemade 12 volt charger with and without an ammeter, we will talk about this later.

How to make a device yourself

How to make a simple homemade one? Several methods are given below (video author - Crazy Hands).

Charger for battery from PC power supply

A good 12 volt one can be built using a working power supply from a computer and an ammeter. This rectifier with ammeter is suitable for almost all batteries.

Almost every power supply is equipped with a PWM - a working controller on a chip. To properly charge the battery, you need about 10 current (from a full battery charge). So if you have a power supply greater than 150W, you can use it.

1. The wires should be removed from the -5 volt, -12 volt, +5V and +12V connectors.
2. After this, resistor R1 is unsoldered; instead, a 27 kOhm resistor should be installed. Also, output 16 must be disconnected from the main drive.
3. Next, on the back side of the power supply you need to mount a current regulator of type R10, and also run two wires - the network wire and for connecting to the terminals. Before making a rectifier, it is advisable to prepare a block of resistors. To make it, you just need to connect two resistors in parallel to measure current, the power of which will be 5 W.
4. To set the rectifier to 12 volts, you also need to install another resistor on the board - a trimmer. To avoid possible connections between the electrical circuit and the housing, remove a small portion of the trace.
5. Next, in the diagram it is necessary to tin and solder the wiring on pins 14, 15, 16 and 1. Special clamps must be mounted on the pins so that the terminal can be hooked. In order not to confuse plus and minus, the wires should be marked; for this you can use insulating tubes.

If you will only use a 12-volt do-it-yourself charger to charge the battery, then you will not need an ammeter and voltmeter. Using an ammeter will allow you to know the exact state of charge of the battery. If the dial scale on the ammeter does not fit, then you can draw your own on the computer. The printed scale is installed in the ammeter.

The simplest memory using an adapter

You can also make a device where the main function of the current source will be performed by a 12 volt adapter. This device is quite simple; its manufacture does not require a special circuit. One important point should be taken into account - the voltage indicator in the source must correspond to the battery voltage. If these indicators differ, then you will not be able to charge the battery.

1. Take the adapter; the end of its wire should be cut and exposed to 5 cm.
2. Then the wires with different charges should be moved away from each other by about 35-40 cm.
3. Now you should install clamps on the ends of the wires, as in the previous case, they should be marked in advance, otherwise you may get confused later. These clamps are connected to the battery one by one, only after that it will be possible to turn on the adapter.

In general, the method is simple, but the difficulty of the method is to choose the right source. If during charging you notice that the battery gets very hot, you need to interrupt this process for a few minutes.

Charger from a household light bulb and diode

This method is one of the simplest. To build such a device, prepare in advance:

• a regular lamp, high power is welcome, as it affects the charging speed (up to 200 W);
• a diode through which current flows in one direction, for example, such diodes are installed in laptop chargers;
• plug and cable.

The connection procedure is quite simple. A more detailed diagram is presented in the video at the end of the article.

Conclusion

Please note that in order to make a high-quality memory, it is not enough just to read this article. You must have certain knowledge and skills and familiarize yourself with the videos presented here in detail. An incorrectly assembled device can damage the battery. On sale in the automotive market you can find inexpensive and high-quality chargers that will last for many years.

Video “How to build a charger from a diode and a light bulb?”

Find out how to do this type of exercise correctly from the video below (video author: Dmitry Vorobyev).

Every motorist sooner or later has problems with the battery. I did not escape this fate either. After 10 minutes of unsuccessful attempts to start my car, I decided that I needed to purchase or make my own charger. In the evening, after checking out the garage and finding a suitable transformer there, I decided to do the charging myself.

There, among the unnecessary junk, I also found a voltage stabilizer from an old TV, which, in my opinion, would work wonderfully as a housing.

Having scoured the vast expanses of the Internet and really assessed my strengths, I probably chose the simplest scheme.

After printing out the diagram, I went to a neighbor who is interested in radio electronics. Within 15 minutes, he collected the necessary parts for me, cut off a piece of foil PCB and gave me a marker for drawing circuit boards. Having spent about an hour, I drew an acceptable board (the dimensions of the case allow for spacious installation). I won’t tell you how to etch the board, there is a lot of information about this. I took my creation to my neighbor, and he etched it for me. In principle, you could buy a circuit board and do everything on it, but as they say to a gift horse...
Having drilled all the necessary holes and displayed the pinout of the transistors on the monitor screen, I took up the soldering iron and after about an hour I had a finished board.

A diode bridge can be purchased on the market, the main thing is that it is designed for a current of at least 10 amperes. I found D 242 diodes, their characteristics are quite suitable, and I soldered a diode bridge on a piece of PCB.

The thyristor must be installed on a radiator, since it gets noticeably hot during operation.

Separately, I must say about the ammeter. I had to buy it in a store, where the sales consultant also picked up the shunt. I decided to modify the circuit a little and add a switch so that I could measure the voltage on the battery. Here, too, a shunt was needed, but when measuring voltage, it is connected not in parallel, but in series. The calculation formula can be found on the Internet; I would add that the dissipation power of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but my 4-watt shunt was heating up. The reason is unknown to me, I don’t have enough experience in such matters, but having decided that I mainly needed the readings of an ammeter, and not a voltmeter, I decided on it. Moreover, in voltmeter mode the shunt noticeably warmed up within 30-40 seconds. So, having collected everything I needed and checked everything on the stool, I took up the body. Having completely disassembled the stabilizer, I took out all its contents.

Having marked the front wall, I drilled holes for the variable resistor and switch, then using a small diameter drill around the circumference I drilled holes for the ammeter. Sharp edges were finished with a file.

After racking my brains a bit over the location of the transformer and radiator with thyristor, I settled on this option.

I bought a couple more crocodile clips and everything is ready to charge. The peculiarity of this circuit is that it only works under load, so after assembling the device and not finding voltage at the terminals with a voltmeter, do not rush to scold me. Just hang at least a car light bulb on the terminals, and you will be happy.

Take a transformer with a voltage on the secondary winding of 20-24 volts. Zener diode D 814. All other elements are indicated in the diagram.

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 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:

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 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 battery charger 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 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:

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.