Homemade car battery charger circuit. How battery chargers work and work. Story about a homemade device

The battery is charged in the vehicle by the generator while the vehicle is in motion. However, as a safety element, a monitoring relay is included in the circuit, which provides an output voltage value from the generator at the level of 14 ± 0.3V.

Since it is known that a sufficient level for full and quick charging of the battery should be at the level of 14.5 V, it is obvious that the battery will need help to fill the entire capacity. In this case, you will need either a store device, or you need to make a do-it-yourself car battery charger at home.

In warmer months, even a half-discharged car battery will start the engine. During frosts, the situation is worse, because at negative temperatures, the capacity decreases, and at the same time, starting currents increase. By increasing the viscosity of the cold oil, more force is required to untwist the crankshaft. This means that in the cold season, the battery needs a maximum charge.

A large number of different options for homemade chargers allows you to choose a circuit for different levels of knowledge and skill of the manufacturer. There is even an option in which the car is manufactured using a powerful diode and an electric heater. A two-kilowatt heater, connected to a 220 V household network, in a series circuit with a diode and a battery, will give the latter a little more than 4 A of current. During the night, the circuit will "wind up" 15 kW, but the battery will receive a full charge. Although the overall system efficiency is unlikely to exceed 1%.

Those who are going to make a simple do-it-yourself battery charger with transistors should be aware that such devices can overheat significantly. They also have problems with incorrect polarity and accidental short circuits.

For thyristor and triac circuits, the main problems are charge stability and noise. On the negative side, there are also radio interference, which can be eliminated with a ferrite filter, and polarity problems.

You can find a lot of proposals for converting a computer power supply into a homemade battery charger. But you need to know that although the structural diagrams of these devices are similar, the electrical ones have significant differences. For the correct alteration, you will need sufficient experience in working with circuits. Not always blind copying with such alterations leads to the desired result.

Circuit diagram on capacitors

The most interesting may be the capacitor circuit of a homemade charger for a car battery. It has a high efficiency, does not overheat, produces a stable current, regardless of the battery charge level and possible problems with network fluctuations, and also tolerates short-term short circuits.

Visually, the picture seems too cumbersome, but with detailed analysis, all areas become clear. It is even equipped with a shutdown algorithm when the battery is fully charged.

Current limiter

For capacitor charging, the regulation of the current strength and its stability is ensured by the series connection of the transformer winding with ballast capacitors. At the same time, the direct dependence of the battery charging current and the capacitance of the capacitors is observed. Increasing the latter, we get a larger amperage.

In theory, this circuit can already work as a battery charge, but the problem will be in its reliability. Poor contact with the battery electrodes will destroy unprotected transformers and capacitors.

Any student studying physics will be able to calculate the required capacitance for capacitors C = 1 / (2πvU). However, it will be faster to do this using a prepared table:

In the circuit, you can reduce the number of capacitors. To do this, they are connected in groups or using switches (toggle switches).

Reverse polarity protection in the charger

In order not to have problems with reversing the polarity of the contacts, there is a relay P3 in the circuit. Incorrectly connected wires will be protected by the VD13 diode. It will not let the current flow in the wrong direction and will not allow the K3.1 contact to close, respectively, the wrong charge will not go to the battery.

If the polarity is observed, the relay will close and charging will begin. This circuit can be used on any of the types of home-made chargers, even with thyristors, even with transistors.

Switch S3 controls the voltage in the circuit. The lower circuit gives the voltage value (V), and with the upper connection of the contacts, we get the current level (A). If the device is connected only to a battery without being connected to a household network, then you can find out the battery voltage in the corresponding switch position. The head is an M24 microammeter.

Self-made charging automation

As a power supply for the amplifier, we select a nine-volt 142EN8G circuit. This choice is based on its characteristics. Indeed, with temperature fluctuations of the board case, even by ten degrees, voltage fluctuations at the output of the device are reduced to an error in hundredths of a volt.

Self-disconnection is triggered at a voltage parameter of 15.5 V. This part of the circuit is labeled A1.1. The fourth pin of the microcircuit (4) is connected to the divider R8, R7 where a voltage of 4.5 V comes out to it. Another divider is connected to the resistors R4-R5-R6. As a setting for this circuit, the adjustment of resistor R5 is applied to indicate the overshoot level. With the help of R9 in the microcircuit, the lower level of switching on the device is controlled, which is carried out at 12.5 V. Resistor R9 and diode VD7 provide a voltage interval for uninterrupted charging.

The algorithm of the circuit is quite simple. By connecting to the charger, the voltage level is monitored. If it is below 16.5 V, then the command to open the transistor VT1 passes through the circuit, which, in turn, starts the connection of relay P1. After that, the primary winding of the installed transformer is connected, and the battery charging process is started.

After gaining the full capacity and obtaining the voltage output parameter at the level of 16.5 V, then the voltage in the circuit is lowered in order to keep the transistor VT1 open. The relay conducts a trip. The current flow to the terminals is reduced to half ampere. The charging cycle starts again only after the voltage at the battery terminals has dropped to 12.5 V, then the charging supply is resumed.

This is how the machine controls the possibility of not recharging the battery. The circuit can be left in working order even for several months. This option will be especially relevant for those who use the car seasonally.

Charger layout

A VZ-38 milliammeter can serve as a case for such a device. Remove unnecessary insides, leaving only the arrow indicator. We mount everything except the machine in a hinged way.

The appliance consists of a pair of shields (front and rear), which are fixed with perforated carbon horizontal beams. It is convenient to attach any structural elements through such holes. A 2mm aluminum plate is used to position the power transformer. It is attached with self-tapping screws to the bottom of the device.

A fiberglass plate with relays and capacitors is mounted on the upper plane. The perforated ribs also have an automatic board. The relays and capacitors of this element are connected using a standard connector.

A radiator on the back wall will help to reduce the heating of the diodes. In this area, it will be appropriate to place fuses and a powerful plug. It can be taken from the computer's power supply. To hold down the power diodes, we use two clamping bars. Their use will allow rational use of space and reduce heat generation inside the unit.

It is desirable to carry out the installation using intuitive wire colors. We take red as positive, blue for negative, and select the alternating voltage using, for example, brown. The section in all cases must be more than 1 mm.

The ammeter reading is calibrated using a shunt. One of its ends is soldered to the relay contact P3, and the other is soldered to the positive output terminal.

Components

Let's analyze the insides of the device, which form the basis of the charger.

Printed circuit board

Fiberglass is the basis for the printed circuit board, which works as protection against voltage surges and connection problems. The image was formed with a step of 2.5 mm. This circuit can be made in a domestic environment without any problems.

Arrangement of elements in reality Soldering line Manual soldering board

There is even a schematic plan with highlighted elements on it. A clean image is used to apply it to a substrate using powder printing on laser printers. For the manual method of applying tracks, another image is suitable.

Graduation scale

The indication of the installed milliammeter VZ-38 does not correspond to the real readings given by the device. For correction and correct calibration, it is necessary to glue a new scale to the indicator base behind the arrow.

The updated information will be accurate to 0.2 V.

Connecting cables

The contacts that will go out to connect to the battery must have a spring clip with teeth ("crocodile") at the ends. To distinguish between the poles, it is advisable to immediately pick up the positive part in red, and take the negative cable with a clip in blue or black.

The cable section must be more than 1 mm. To connect to the household network, a standard non-separable cable with a plug from any old office equipment is used.

Electric elements of homemade battery charging

TN 61-220 is suitable as a power transformer, because the output current will be at the level of 6 A. For capacitors, the voltage must be more than 350 V. We take the MBGCH type for the circuit for C4 to C9. Diodes from the 2nd to the 5th are needed to withstand a ten-ampere current. 11th and 7th, you can take any impulse. VD1 is an LED, and the 9th can be analogous to KIPD29.

For the rest, you need to focus on an input parameter that allows a current of 1A. In relay P1, you can use two LEDs with different color characteristics, or you can use a binary LED.

The operational amplifier AN6551 can be replaced by a domestic analogue of the KR1005UD1. They can be found in older audio amplifiers. The first and second relays are selected from the range of 9-12 V and a current of 1 A. For several contact groups in the relay device, we use parallelization.

Setting up and running

If everything is done without errors, then the circuit will work immediately. The threshold voltage is adjusted using the resistor R5. It will help put the charging in the correct low current mode.

At the moment, there are many different devices that operate on batteries. And it is all the more annoying when, at the most inopportune moment, our device stops working, because the batteries simply sat down, and their charge is not enough for the normal functioning of the device.

Buying new batteries every time is quite costly, but trying to make a homemade device for charging finger batteries with your own hands is quite worth it.

Many craftsmen note that it is preferable to charge such batteries (AA or AAA) using direct current, because this mode is most beneficial in terms of safety for the batteries themselves. In general, the transferred charge power from the network is about 1.2-1.6 times the capacity of the battery itself. For example, a nickel-cadmium battery with a capacity of 1A / h will be charged with a current of 1.6 A / h. Moreover, the lower the indicator of this power, the better for the charging process.

In the modern world, there are quite a few household appliances equipped with a special time timer that counts down a certain period, then signaling its end. When making do-it-yourself devices for charging finger batteries, you can also apply this technology, which will notify you of the end of the battery charging process.

AA is a device that generates constant current, charging power up to 3 A / h. In the manufacture, the most common, even classic, scheme was used, which you see below. The basis, in this case, is the VT1 transistor.

The voltage across this transistor is indicated by a red VD5 LED, which acts as an indicator when the device is connected to the network. Resistor R1 sets a certain power of the currents passing through this LED, as a result of which the voltage in it fluctuates. The collector current value is formed by the resistance from R2 to R5, which are included in VT2 - the so-called "emitter circuit". At the same time, changing the resistance values, you can control the degree of charge. R2 is constantly included in VT1, setting a constant current with a minimum value of 70 mA. To increase the charging power, it is necessary to connect the rest of the resistors, i.e. R3, R4 and R5.

Read also: We make the simplest converter 12V - 220V with our own hands

It should be noted that the charger only functions when the batteries are connected.

After connecting the device to the network, a certain voltage appears on the resistor R2, which is transmitted to the transistor VT2. Then, the current flows further, as a result of which the VD7 LED starts to light up intensively.

Story about a homemade device

USB charging

Can make a charger for nickel cadmium batteries based on conventional USB port... In this case, they will be charged with a current of approximately 100 mA. The scheme, in this case, will be as follows:

At the moment, there are many different chargers sold in stores, but their cost can be quite high. Considering that the main meaning of various homemade products is precisely to save money, then self-assembly is even more expedient in this case.

This circuit can be improved by adding an additional circuit to charge a pair of AA batteries. Here's what happened in the end:

To make it clearer, here are the components that were used in the assembly process:

It is clear that we cannot do without elementary tools, so before starting the assembly, you need to make sure that you have everything you need:

• soldering iron;
• solder;
• flux;
• tester;
• tweezers;
• various screwdrivers and a knife.

Read also: We will find out everything about step-down transformers 220-12 volts

Interesting material about making with your own hands, we recommend for viewing

A tester is needed in order to check the performance of our radio components. To do this, you need to compare their resistance, and then check with the nominal value.

For assembly, we also need a case and a battery compartment. The latter can be taken from the Tetris simulator for children, and the body can be made from a regular plastic case (6.5cm / 4.5cm / 2cm).

We attach the battery compartment to the case using screws. As a basis for the circuit, the board from the Dandy prefix, which needs to be cut out, is perfect. We remove all unnecessary components, leaving only the power socket. The next step is to solder all the parts based on our diagram.

The power cord for the device can be taken with a regular cord from a computer mouse with a USB input, as well as a part of the power cord with a plug. When soldering, the polarity must be strictly observed, i.e. solder plus to plus, etc. We connect the cable to USB, checking the voltage that is supplied to the plug. The tester should read 5V.

Every owner of a used car is faced with the need to recharge the battery. In addition, rechargeable batteries are often used as a backup (or main) source of electricity in a garage, shed, or dacha without a centralized electricity supply.

To restore the battery charge, you can buy a ready-made one, there is no shortage in the offer.

Used to charge the car battery

However, many home craftsmen prefer to make their own hands. If you have a radio engineering education, you can calculate the circuit yourself. And for most hobbyists who know how to hold a soldering iron in their hands, we offer a couple of simple designs.

First of all, let's decide which batteries you need to charge. Typically, these are acidic starter batteries used in automobiles.

Such a battery can be purchased inexpensively at a car dealership, or you can use an old one left over from a replacement on your car. a used one may not be able to work as a starter, but it is easy to connect a lighting device (especially an LED) or a radio receiver in the country to it.

How to calculate a homemade charger correctly?

The first rule to learn is the magnitude of the charge voltage.
Lead batteries have an operating voltage of 12.5 volts. But for charging, you need to apply a voltage in the range of 13.9 - 14.4 volts. Accordingly, the charger must be made with just such output parameters.

The next value is power.
More precisely, the current strength at which there will be no voltage drop at the output terminals of the charger. If you do not plan to charge batteries with a capacity of more than 65 a / h, a stable current of 12 A.

Important! This value should be provided precisely by the output stage of the charger, the current at the input of 220 volts will be several times less.

A low-power charger can also charge high-capacity batteries. Only it will take much more time.

It will also be useful to have an automatic shutdown function when the normal charge level is reached, protection of the device from reverse current (the battery is a powerful source of energy that can damage the output stage of an incorrectly designed charger), or at least control of the output voltage, and preferably the current.

If, in addition to the fuse, you install protection against polarity reversal and short circuit - great. However, any modification complicates the device and increases its cost.

Not every car owner has a car battery charger available. Many do not consider it necessary to purchase such a unit, believing that they will not need it. However, as practice shows, at least once in his life, every driver finds himself in a situation where it is necessary to drive as well.

It is not necessary to purchase a new factory charger, you can make it yourself from, for example, old electrical appliances. There are many options for making do-it-yourself car chargers, but most of them have significant drawbacks.

• The transformer is used type ТН61-22, the windings are connected in series. The efficiency of charging is not less than 0.8, the current strength is not more than 6 amperes, so a transformer with a power of 150 watts is perfect. The transformer winding must provide a voltage of up to 20 volts at a current strength of up to 8 amperes. In the absence of a ready-made model, you can take any transformer of the required power and wind up secondary processing. To calculate the number of turns, use a specially designed calculator that can be found on sites on the Internet.
• Capacitors from the MBGCH series are suitable, designed for a current with a voltage of at least 350 volts. If the capacitor supports operation with alternating current, then it is suitable for creating a charger.
• Diodes will do absolutely any, but they must be rated for a current of up to 10 amperes.
• An analogue of AN6551 - KR1005UD1 can be selected as an operational amplifier. It was this model that was previously inserted into the VM-12 tape recorders. It is very good in that it does not require a bipolar power supply during operation, as well as correction circuits. KR1005UD1 operates at voltage fluctuations of more than 7 V. In general, this model can be replaced by any similar one. For example, it can be LM158, LM358 and LM258, but then you have to change the printed circuit board pattern.
• Any electromagnetic head, for example M24, is suitable for measuring voltage and current. If you are not interested in voltage readings, then simply install an ammeter that is designed for direct current. Otherwise, the voltage is monitored with a tester or multimeter.

The video shows the creation of a car charger:

Checking and setting

In the event that all the elements are in good order and the assembly took place without errors, then the circuit should work immediately. And the car owner only needs to set the voltage threshold using a resistor. When charging reaches this device, it will switch to low current mode.

Adjustment is carried out at the time of charging. But it’s probably better to insure yourself: set up and test protection and regulation schemes. From measuring instruments, this will require a multimeter or tester designed to work with constant voltage.

How to charge the assembled device

There are certain rules that must be followed when using a homemade car charger.

It is important to clean it of dust and dirt even before charging. Then wipe with a soda solution in order to remove acid residues. If there are acid particles on the battery, then the soda will begin to foam.

Unscrew the plugs for filling the acids in the battery. This is done so that the gases generated in the battery can escape. Then you should check the amount: if the level is less than optimal, add distilled water.

After that, use the switch to set a certain reading of the charge current, connect the assembled device, taking into account the polarity. Accordingly, the positive charging terminal must be connected to the positive terminal of the battery. Finding the switch in the down position will bring the arrow of the device to the current voltage indicator. The voltmeter begins to indicate voltage at the same time.

If it has a capacity of 50 Ah, at the moment it is 50% charged, then you should first set the current to 25 amperes, gradually decreasing it to zero. Automatic charging devices operate on a similar principle. They help to charge the car battery to 100%. True, such devices are very expensive. With timely charging, such an expensive device is not needed.

Summing up, we can say that, using even used parts from old devices, you can assemble a pretty decent charger for a car battery. If you do not have the ability to do it yourself, then you can always find such a craftsman in every garage cooperative. And it will certainly cost significantly less than buying a new factory device.