How to assemble a charger for a car. DIY car battery charger

Automatic devices are simple in design, but very reliable in operation. Their design was created using a simple design without unnecessary electronic additions. They are designed for simple charging of batteries of any vehicles.

Pros:

1. The charger will last for many years with proper use and proper maintenance.

Minuses:

1. Lack of any protection.
2. Eliminating discharge mode and the possibility of reconditioning the battery.
3. Heavy weight.
4. Quite a high cost.

The classic charger consists of the following key elements:

1. Transformer.
2. Rectifier.
3. Adjustment block.

Such a device produces direct current at a voltage of 14.4V, not 12V. Therefore, according to the laws of physics, it is impossible to charge one device with another if they have the same voltage. Based on the above, the optimal value for such a device is 14.4 Volts.

The key components of any charger are:

• transformer;
• mains plug;
• fuse (provides short circuit protection);
• wire rheostat (adjusts the charging current);
• ammeter (shows the strength of electric current);
• rectifier (converts alternating current to direct current);
• rheostat (regulates current and voltage in the electrical circuit);
• bulb;
• switch;
• frame;

Wires for connection

To connect any charger, as a rule, red and black wires are used, red is positive, black is negative.

When choosing cables to connect a charger or starting device, you must select a cross-section of at least 1 mm2.

Attention. Further information is provided for informational purposes only. Whatever you want to bring to life, you do at your own discretion. Incorrect or inept handling of certain spare parts and devices will cause them to malfunction.

Having looked at the available types of chargers, let’s move on directly to making them ourselves.

Charging the battery from the computer power supply

To charge any battery, 5-6 ampere hours is enough, this is about 10% of the capacity of the entire battery. Any power supply with a capacity of 150 W or more can produce it.

So, let's look at 2 ways to make your own charger from a computer power supply.

Method one

For manufacturing you need the following parts:

• power supply, power from 150 W;
• resistor 27 kOhm;
• current regulator R10 or resistor block;
• wires with a length of 1 meter;

Work progress:

1. To start we will need to disassemble the power supply.
2. We extract wires we do not use, namely -5v, +5v, -12v and +12v.
3. We replace the resistor R1 to a pre-prepared 27 kOhm resistor.
4. Removing the wires 14 and 15, and 16 we simply turn off.
5. From the block We bring out the power cord and wires to the battery.
6. Install the current regulator R10. In the absence of such a regulator, you can make a homemade resistor block. It will consist of two 5 W resistors, which will be connected in parallel.
7. To set up the charger, We install a variable resistor in the board.
8. To exits 1,14,15,16 We solder the wires and use a resistor to set the voltage to 13.8-14.5V.
9. At the end of the wires connect the terminals.
10. We delete the remaining unnecessary tracks.

Important: adhere to the complete instructions, the slightest deviation can lead to burnout of the device.

Method two

To manufacture our device using this method, you will need a slightly more powerful power supply, namely 350 W. Since it can output 12-14 amps which will satisfy our needs.

Work progress:

1. In computer power supplies The pulse transformer has several windings, one of them is 12V, and the second is 5V. To make our device, you only need a 12V winding.
2. To run our block you will need to find the green wire and connect it to the black wire. If you use a cheap Chinese unit, there may be a gray wire instead of a green one.
3. If you have an old power supply and with a power button, the above procedure is not needed.
4. Further, we make 2 thick busbars from the yellow and black wires, and cut off the unnecessary wires. A black tire will be a minus, a yellow one will be a plus.
5. To improve reliability Our device can be swapped. The fact is that the 5V bus has a more powerful diode than the 12V.
6. Since the power supply has a built-in fan, then he is not afraid of overheating.

Method three

For manufacturing we will need the following parts:

• power supply, power 230 W;
• board with TL 431 chip;
• resistor 2.7 kOhm;
• resistor 200 Ohm power 2 W;
• 68 Ohm resistor with a power of 0.5 W;
• resistor 0.47 Ohm power 1 W;
• 4-pin relay;
• 2 diodes 1N4007 or similar diodes;
• resistor 1kOhm;
• bright LED;
• wire length of at least 1 meter and cross-section of at least 2.5 mm 2, with terminals;

Work progress:

1. Desoldering all wires except 4 black and 2 yellow wires, since they carry power.
2. Close the contacts with a jumper, responsible for overvoltage protection so that our power supply does not turn off due to overvoltage.
3. We replace it on a board with a TL 431 chip built-in resistor for a 2.7 kOhm resistor, to set the output voltage to 14.4 V.
4. Add a 200 Ohm resistor with a power of 2 W per output from the 12V channel, to stabilize the voltage.
5. Add a 68 Ohm resistor with a power of 0.5 W per output from the 5V channel, to stabilize the voltage.
6. Solder the transistor on the board with the TL 431 chip, to eliminate obstacles when setting the voltage.
7. Replace the standard resistor, in the primary circuit of the transformer winding, to a 0.47 Ohm resistor with a power of 1 W.
8. Assembling a protection scheme from incorrect connection to the battery.
9. Unsolder from the power supply unnecessary parts.
10. We output necessary wires from the power supply.
11. Solder the terminals to the wires.

For ease of use of the charger, connect an ammeter.

The advantage of such a homemade device is the inability to recharge the battery.

The simplest device using an adapter

Now consider the case when there is no unnecessary power supply available, our battery is dead and needs to be charged.

Every good owner or fan of all kinds of electronic devices has an adapter for recharging autonomous equipment. Any 12V adapter can be used to charge a car battery.

The main condition for such charging is that the voltage supplied by the source is no less than that of the battery.

Work progress:

1. Necessary cut off the connector from the end of the adapter wire and peel off the insulation at least 5 cm.
2. Since the wire goes double, it is necessary to divide it. The distance between the ends of the 2 wires must be at least 50 cm.
3. Solder or tape to the ends of the terminal wire for secure fixation on the battery.
4. If the terminals are the same, then you need to take care of putting insignia on them.
5. The biggest disadvantage of this method consists of constant monitoring of the temperature of the adapter. Since if the adapter burns out, it can render the battery unusable.

Before connecting the adapter to the network, you must first connect it to the battery.

Charger made from a diode and a household light bulb

Diode is a semiconductor electronic device that is capable of conducting current in one direction and has a resistance equal to zero.

The charging adapter for the laptop will be used as a diode.

To manufacture this type of device, we will need:

• charging adapter for laptop;
• bulb;
• wires from 1 m long;

Each car charger produces about 20V voltage. Since the diode replaces the adapter and passes voltage only in one direction, it is protected from short circuits that can occur if connected incorrectly.

The higher the power of the light bulb, the faster the battery charges.

Work progress:

1. To the positive wire of the laptop adapter We connect our light bulb.
2. From a light bulb we throw the wire to the positive.
3. Disadvantage from the adapter directly connect to the battery.

If connected correctly, our light bulb will glow because the current at the terminals is low and the voltage is high.

Also, you need to remember that proper charging requires an average current of 2-3 amperes. Connecting a high-power light bulb leads to an increase in current strength, and this, in turn, has a detrimental effect on the battery.

Based on this, you can connect a high-power light bulb only in special cases.

This method involves constantly monitoring and measuring the voltage at the terminals. Overcharging the battery will produce excessive amounts of hydrogen and may damage it.

When charging the battery in this way, try to stay near the device, since leaving it temporarily unattended can lead to failure of the device and the battery.

Checking and setting

To test our device, you must have a working car light bulb. First, using a wire, we connect our light bulb to the charger, remembering to observe the polarity. We plug in the charger and the light comes on. Everything is working.

Each time, before using a homemade charging device, check its functionality. This check will eliminate all possibilities of damaging your battery.

How to charge a car battery

Quite a large number of car owners consider charging the battery a very simple matter.

But in this process there are a number of nuances on which the long-term operation of the battery depends:

Before you put the battery on charge, you need to carry out a number of necessary actions:

1. Use chemical resistant gloves and goggles.
2. After removing the battery carefully inspect it for signs of mechanical damage and traces of liquid leakage.
3. Unscrew the protective caps, to release the generated hydrogen, to avoid boiling the battery.
4. Take a close look at the liquid. It should be transparent, without flakes. If the liquid is dark in color and there are signs of sediment, seek professional help immediately.
5. Check fluid level. Based on current standards, there are marks on the side of the battery, “minimum and maximum,” and if the fluid level is below the required level, it must be refilled.
6. Flood Only distilled water is needed.
7. Don't turn it on charger into the network until the crocodiles are connected to the terminals.
8. Observe polarity when connecting alligator clips to the terminals.
9. If during charging If you hear boiling sounds, then unplug the device, let the battery cool down, check the fluid level and then you can reconnect the charger to the network.
10. Make sure that the battery is not overcharged, since the condition of its plates depends on this.
11. Charge the battery only in well-ventilated areas, as toxic substances are released during the charging process.
12. Electrical network must have installed circuit breakers that turn off the network in the event of a short circuit.

After you charge the battery, over time the current will drop and the voltage at the terminals will increase. When the voltage reaches 14.5V, charging should be stopped by disconnecting from the network. When the voltage reaches more than 14.5 V, the battery will begin to boil and the plates will become free of liquid.

Basic operating modes of the device for the presets included in the program.

>>
Charging mode - “Charge” menu. For batteries with capacities from 7Ah to 12Ah, the IUoU algorithm is set by default. This means:

- First step- charging with a stable current of 0.1C until the voltage reaches 14.6V

- second phase-charging with a stable voltage of 14.6V until the current drops to 0.02C

- third stage- maintaining a stable voltage of 13.8V until the current drops to 0.01C. Here C is the battery capacity in Ah.

- fourth stage- recharging. At this stage, the voltage on the battery is monitored. If it drops below 12.7V, the charge starts from the very beginning.

For starter batteries we use the IUIoU algorithm. Instead of the third stage, the current is stabilized at 0.02C until the battery voltage reaches 16V or after about 2 hours. At the end of this stage, charging stops and recharging begins.

>> Desulfation mode - “Training” menu. Here the training cycle is carried out: 10 seconds - discharge with a current of 0.01C, 5 seconds - charge with a current of 0.1C. The charge-discharge cycle continues until the battery voltage rises to 14.6V. Next is the usual charge.

>>
The battery test mode allows you to evaluate the degree of battery discharge. The battery is loaded with a current of 0.01C for 15 seconds, then the voltage measurement mode on the battery is turned on.

>> Control-training cycle. If you first connect an additional load and turn on the “Charge” or “Training” mode, then in this case, the battery will first be discharged to a voltage of 10.8 V, and then the corresponding selected mode will be turned on. In this case, the current and discharge time are measured, thus calculating the approximate capacity of the battery. These parameters are displayed on the display after charging is complete (when the message “Battery charged” appears) when you press the “select” button. As an additional load, you can use a car incandescent lamp. Its power is selected based on the required discharge current. Usually it is set equal to 0.1C - 0.05C (10 or 20 hour discharge current).

Charging circuit diagram for 12V battery

Schematic diagram of an automatic car charger

Drawing of an automatic car charger board

The basis of the circuit is the AtMega16 microcontroller. Navigation through the menu is carried out using the buttons " left», « right», « choice" The “reset” button exits any operating mode of the charger to the main menu. The main parameters of charging algorithms can be configured for a specific battery; for this, there are two customizable profiles in the menu. The configured parameters are saved in non-volatile memory.

To get to the settings menu, you need to select any of the profiles and press the “ choice", choose " installations», « profile parameters", profile P1 or P2. Having selected the desired option, click “ choice" Arrows " left" or " right» will change to arrows « up" or " down", which means the parameter is ready to change. Select the desired value using the “left” or “right” buttons, confirm with the “ choice" The display will show “Saved”, indicating that the value has been written to the EEPROM. Read more about the setup on the forum.

The control of the main processes is entrusted to the microcontroller. A control program is written into its memory, in which all the algorithms are embedded. The power supply is controlled using PWM from the PD7 pin of the MK and a simple DAC based on elements R4, C9, R7, C11. The measurement of battery voltage and charging current is carried out using the microcontroller itself - a built-in ADC and a controlled differential amplifier. The battery voltage is supplied to the ADC input from the divider R10 R11.

Charging and discharging current are measured as follows. The voltage drop from the measuring resistor R8 through dividers R5 R6 R10 R11 is supplied to the amplifier stage, which is located inside the MK and connected to pins PA2, PA3. Its gain is set programmatically, depending on the measured current. For currents less than 1A, the gain factor (GC) is set equal to 200, for currents above 1A GC=10. All information is displayed on the LCD connected to ports PB1-PB7 via a four-wire bus.

Protection against polarity reversal is carried out on transistor T1, signaling of incorrect connection is carried out on elements VD1, EP1, R13. When the charger is connected to the network, transistor T1 is closed at a low level from the PC5 port, and the battery is disconnected from the charger. It connects only when you select the battery type and charger operating mode in the menu. This also ensures that there is no sparking when the battery is connected. If you try to connect the battery in the wrong polarity, the buzzer EP1 and the red LED VD1 will sound, signaling a possible accident.

During the charging process, the charging current is constantly monitored. If it becomes equal to zero (the terminals have been removed from the battery), the device automatically goes to the main menu, stopping the charge and disconnecting the battery. Transistor T2 and resistor R12 form a discharge circuit, which participates in the charge-discharge cycle of the desulfating charge and in the battery test mode. The discharge current of 0.01C is set using PWM from the PD5 port. The cooler automatically turns off when the charging current drops below 1.8A. The cooler is controlled by port PD4 and transistor VT1.

Resistor R8 is ceramic or wire, with a power of at least 10 W, R12 is also 10 W. The rest are 0.125W. Resistors R5, R6, R10 and R11 must be used with a tolerance of at least 0.5%. The accuracy of the measurements will depend on this. It is advisable to use transistors T1 and T1 as shown in the diagram. But if you have to select a replacement, then you need to take into account that they must open with a gate voltage of 5V and, of course, must withstand a current of at least 10A. For example, transistors marked 40N03GP, which are sometimes used in the same ATX format power supplies, in the 3.3V stabilization circuit.

LCD– WH1602 or similar, on the controller HD44780, KS0066 or compatible with them. Unfortunately, these indicators may have different pin locations, so you may have to design a printed circuit board for your instance

Converting an ATX power supply to a charger

Electrical circuit for modification of standard ATX

It is better to use precision resistors in the control circuit, as indicated in the description. When using trimmers, the parameters are not stable. tested from my own experience. When testing this charger, it carried out a full cycle of discharging and charging the battery (discharging to 10.8V and charging in training mode, it took about a day). The heating of the computer's ATX power supply is no more than 60 degrees, and that of the MK module is even less.

There were no problems with the setup, it started right away, it just needed some adjustment to the most accurate readings. After demonstrating the work of this charging machine to a friend who was a car enthusiast, an application was immediately received for the production of another copy. Author of the scheme - Slon , assembly and testing - sterc .

Discuss the article AUTOMATIC CAR CHARGER

Many car enthusiasts have a need to charge the battery. Some use branded chargers for these purposes, others use homemade chargers made at home. How to make and how to properly charge the battery with such a device? We will talk about this below.

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Design and principle of operation of the charger

A simple battery charger is a device used to restore battery charge. The essence of the functioning of any charger is that this device allows you to convert voltage from a 220-volt household network into the voltage required for. Today there are many types of chargers, but any device is based on two main components - a transformer device and a rectifier (the author of the video on how to choose a charging device is the Battery Manager channel).

The process itself consists of several stages:

• when recharging the battery, the charging current parameter decreases and the resistance level increases;
• at the moment when the voltage parameter approaches 12 volts, the charging current level reaches zero - at this moment the battery will be fully charged, and the charger can be turned off.

Instructions for making a simple charger with your own hands

If you want to make a charger for a 12 or 6 volt car battery, then we can help you with this. Of course, if you have never encountered such a need before, but want to get a functional device, then it is better to purchase an automatic one. After all, a homemade charger for a car battery will not have the same functions as a branded device.

Tools and materials

So, to make a battery charger with your own hands, you will need the following items:

• soldering iron with consumables;
• textolite plate;
• wire with plug for connecting to a household network;
• radiator from a computer.

Depending on, an ammeter and other components can be additionally used to allow proper charging and charge control. Of course, to make a car charger, you also need to prepare a transformer assembly and a rectifier for charging the battery. By the way, the housing itself can be taken from an old ammeter. The ammeter body has several holes to which you can connect the necessary elements. If you don't have an ammeter, you can find something similar.

Photo gallery “Getting ready for assembly”

Stages

To build a charger for a car battery with your own hands, do the following:

1. So, first you need to work with the transformer. We will show an example of making a homemade charger with a TS-180-2 transformer device - such a device can be removed from an old tube TV. Such devices are equipped with two windings - primary and secondary, and at the output of each secondary component the current is 4.7 amperes and the voltage is 6.4 volts. Accordingly, a homemade charger will produce 12.8 volts, but for this the windings must be connected in series.
2. To connect the windings, you will need a cable whose cross-section will be less than 2.5 mm2.
3. Using a jumper, you need to connect both the secondary and primary components.
4. Then you will need a diode bridge; to equip it, take four diode elements, each of which must be designed to operate under current conditions of at least 10 amperes.
5. The diodes are fixed on the textolite plate, after which they will need to be connected correctly.
6. Cables are connected to the output diode components, with the help of which the homemade charger will be connected to the battery. To measure the voltage level, you can additionally use an electromagnetic head, but if this parameter does not interest you, you can install an ammeter designed for direct current. After completing these steps, the charger will be ready with your own hands (the author of the video about making the simplest device in its design is the Soldering Iron TV channel).

How to charge a battery with a homemade charger?

Now you know how to make a charger for your car at home. But how to use it correctly so that it does not affect the service life of a charged battery?

1. When connecting, you must always observe polarity so as not to mix up the terminals. If you make a mistake and mix up the terminals, you will simply “kill” the battery. So the positive wire from the charger is always connected to the battery positive, and the negative wire to the negative.
2. Never try to test the battery for a spark - despite the fact that there are many recommendations on the Internet regarding this, under no circumstances should you short-circuit the wires. This will negatively affect the operation of the charger and the battery itself in the future.
3. When the device is connected to the battery, it must be disconnected from the network. The same goes for turning it off.
4. When manufacturing and assembling the charger, and during its use, always be careful. To avoid personal injury, always follow safety precautions, particularly when working with electrical components. If errors are made during manufacturing, this can cause not only personal injury, but also failure of the battery as a whole.
5. Never leave a working charger unattended - you need to understand that this is a homemade device and anything can happen during its operation. When recharging, the device and battery should be kept in a ventilated area, as far as possible from explosive materials.

Video “An example of assembling a homemade charger with your own hands”

The video below shows an example of assembling a homemade charger for a car battery using a more complex scheme with basic recommendations and tips (the author of the video is the AKA KASYAN channel).

We have repeatedly talked about all kinds of chargers for car batteries on a pulse basis, and today is no exception. And we will consider the design of an SMPS, which can have an output power of 350-600 watts, but this is not the limit, since the power, if desired, can be increased to 1300-1500 watts, therefore, on such a basis it is possible to build a starting-charger device, because at a voltage of 12 -14 Volts from a 1500 watt unit can draw up to 120 Amperes of current! well of course

The design attracted my attention a month ago, when an article caught my eye on one of the sites. The power regulator circuit seemed quite simple, so I decided to use this circuit for my design, which is very simple and does not require any adjustment. The circuit is designed for charging powerful acid batteries with a capacity of 40-100A/h, implemented on a pulse basis. The main power part of our charger is a mains switching power supply with power

Just recently I decided to make several chargers for car batteries, which I was going to sell on the local market. There were quite beautiful industrial buildings available; all you had to do was make a good filling and that was it. But then I encountered a number of problems, starting from the power supply and ending with the output voltage control unit. I went and bought a good old electronic transformer like Tashibra (Chinese brand) for 105 watts and started reworking it.

A fairly simple automatic charger can be implemented on the LM317 chip, which is a linear voltage regulator with an adjustable output voltage. The microcircuit can also work as a current stabilizer.

A high-quality charger for a car battery can be purchased on the market for $50, and today I will tell you the easiest way to make such a charger with minimal expenditure of money; it is simple and even a novice radio amateur can make it.

The design of a simple charger for car batteries can be implemented in half an hour at minimal cost; the process of assembling such a charger will be described below.

The article discusses a charger (charger) with a simple circuit design for batteries of various classes intended to power the electrical networks of cars, motorcycles, flashlights, etc. The charger is easy to use, does not require adjustments while charging the battery, is not afraid of short circuits, and is simple and cheap to manufacture.

Recently, I came across a diagram of a powerful charger for car batteries with a current of up to 20A on the Internet. In fact, this is a powerful regulated power supply assembled with just two transistors. The main advantage of the circuit is the minimum number of components used, but the components themselves are quite expensive, we are talking about transistors.

Naturally, everyone in the car has cigarette lighter chargers for all kinds of devices: navigator, phone, etc. The cigarette lighter is naturally not without dimensions, and especially since there is only one (or rather, a cigarette lighter socket), and if there is also a person who smokes, then the cigarette lighter itself must be taken out somewhere and put somewhere, and if you really need to connect something to the charger, then using the cigarette lighter for its intended purpose is simply impossible , you can solve the connection of all kinds of tees with a socket like a cigarette lighter, but it’s like that

Recently I came up with the idea of ​​assembling a car charger based on cheap Chinese power supplies with a price of $5-10. In electronics stores you can now find units that are designed to power LED strips. Since such tapes are powered by 12 Volts, therefore the output voltage of the power supply is also within 12 Volts

I present the design of a simple DC-DC converter that will allow you to charge a mobile phone, tablet computer or any other portable device from a 12-volt car on-board network. The heart of the circuit is a specialized 34063api chip designed specifically for such purposes.

After the article charger from an electronic transformer, many letters were sent to my email address asking me to explain and tell how to power up the circuit of an electronic transformer, and in order not to write to each user separately, I decided to print this article, where I will talk about the main components that need will be modified to increase the output power of the electronic transformer.

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 improvised “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.