When parked for a long time, the car battery will discharge over time. On-board electrical equipment constantly consumes a small current, and a self-discharge process occurs in the battery. But even regular operation of the machine does not always provide a sufficient charge.

This is especially noticeable in winter with short trips. Under such conditions, the generator does not have time to restore the charge spent on the starter. This is where a car battery charger comes in handy., which you can do with your own hands.

Why you need to charge the battery

Modern cars use lead-acid batteries. Their peculiarity is that with a constant weak charge, plate sulfation process. As a result, the battery loses capacity and cannot cope with starting the engine. You can avoid this by regularly charging the battery from the mains. With it, you can recharge the battery and prevent, and in some cases even reverse, the sulfation process.

A DIY battery charger (UZ) is indispensable in cases where you leave the car in the garage for the winter. Due to self-discharge, the battery loses 15-30% capacity per month. Therefore, starting a car at the beginning of the season without pre-charging will not work.

Charge requirements for car batteries

• The presence of automation. The battery is put on charge mainly at night. Therefore, the charger should not require current and voltage control by the car owner.
• Sufficient tension. The power supply (IP) must provide 14.5V. When the voltage drops on the memory, you need to choose a higher voltage power supply.
• Protective system. When the charge current is exceeded, the automation must irreversibly disconnect the battery. Otherwise, the device may fail and even catch fire. The system should be reset to its original state only after human intervention.
• Reverse polarity protection. If the battery terminals are incorrectly connected to the charger, the circuit should instantly turn off. The system described above copes with this task.

Common mistakes in the design of homemade memory

• Connecting the battery to the home electrical network through a diode bridge and a ballast in the form of a capacitor with resistance. The high-capacity paper-oil capacitor required in this case will cost more than a purchased “charge”. This connection scheme creates a large reactive load, which can "to confuse" modern protection devices and electricity meters.
• Creation of a memory device based on a powerful transformer with a primary winding on 220V and secondary to 15V. There will be no problems with the operation of such equipment, and space technology can envy its reliability. But making such a battery charger with your own hands will serve as a clear illustration of the expression "shoot sparrows with a cannon". And the heavy bulky design is not distinguished by ergonomics and ease of use.

Protection scheme

The probability that a short circuit will occur sooner or later at the output of the charger for the battery 100% . The cause may be polarity reversal, a loose terminal, or other operator error. Therefore, it is necessary to start with the design of the protection device (UZ). It should quickly and clearly operate in case of overload and break the output circuit.

There are two designs of US:

• External, made as a separate module. They can be connected to any 14 volt DC source.
• Internal, integrated into the case of a specific "charge".

The classic Schottky diode circuit saves only if the battery is connected incorrectly. But the diodes will simply burn out from overload when connected to a discharged battery or a short circuit at the output of the memory

It is better to use the universal scheme shown in the figure. It uses relay hysteresis and the slow response of an acid battery to power surges.

When the load jumps in the circuit, the voltage on the relay coil drops and it turns off, preventing overload. The problem is that this circuit does not protect against polarity reversal. Also, the system does not finally turn off when the current is exceeded, and not a short circuit. When overloaded, the contacts will begin to “clap” continuously and this process will not stop until they burn. Therefore, another circuit based on a pair of transistors and a relay is considered the best.

The relay winding here is connected by diodes according to the “or” logic circuit to the self-locking circuit and control modules. Before operation, the charger must be configured by connecting a ballast load to it.

What power source to use

A DIY charger requires a power source. Batteries need parameters 14.5-15V / 2-5A (amp hours). Such characteristics are available for switching power supplies (UPS) and blocks on a transformer.

The advantage of the UPS is that it may well already be available. But the complexity of creating a memory for a battery based on it is much higher. Therefore, buying a switching power supply for use in a car charger is not worth it. It is better then to make a simpler and cheaper power source from a transformer and a rectifier.

Battery charger circuit:

Power supply for "charging" from the UPS

The advantage of a PSU from a computer is that it already has a built-in protective circuit. However, you will have to work hard to slightly redo the design. To do this, do the following:

• remove all output wires except yellow (+12V), black (ground) and green (PC turn-on wire).
• short green and black wires;
• install a mains switch (in the absence of a standard one);
• find resistor feedback in chain +12V;
• replace variable resistor on the 10 kOhm;
• turn on the PSU;
• rotating the variable resistor, set the output 14.4 V;
• measure the current resistance of the variable resistor;
• replace the variable resistor with a constant of the same value (tolerance 2%);
• connect a voltmeter to the output of the power supply to control the charging process (optional);
• connect the yellow and black wires into two bundles;
• connect wires with clamps to connect to the terminals.

Tip: Instead of a voltmeter, you can use a universal multimeter. To power it, leave one red wire (+5 V).

Do-it-yourself battery charger is ready. It remains only to connect the device to the mains and charge the battery.

Charger on the transformer

The advantage of a transformer power supply is that its electrical inertia is higher than that of a battery. This improves the safety and reliability of the circuit.

Unlike UPS, there is no built-in protection. Therefore, care must be taken to prevent overloading the do-it-yourself charger. For car batteries, this is also extremely important. Otherwise, during current and voltage overloads, any troubles are possible: from burnout of the windings to splashing of acid and even battery explosion.

ZU from an electronic transformer (Video)

This video talks about adjustable block power supply, the basis of which is a converted electronic 12V transformer with a power of 105 W. In combination with a switching regulator module, a reliable and compact charger is obtained for all types of batteries. 1.4-26V 0-3A.

A homemade power supply consists of two blocks: a transformer and a rectifier.

You can find a finished part with suitable windings or wind it yourself. The second option is more preferable, since finding a transformer with an output 14.3-14.5 volts you are unlikely to succeed. You will have to use ready-made solutions that issue 12.6V. You can increase the voltage by about 0.6 V using a rectifier assembly with a midpoint on Schottky diodes.

The power of the windings must be at least 120 watts, diode parameters - 30 amps / 35 volts. This is enough to properly charge the battery.

You can use a thyristor rectifier. To obtain 14 V at the output, the input AC voltage at the rectifier should be about 24 volts. It will not be difficult to find a transformer with such parameters.

The easiest way- buy an adjustable rectifier for 18 or 24 volts and adjust it so that it gives out 14.4 V

A charger (charger) for a battery is necessary for every car enthusiast, but it costs a lot, and regular preventive trips to a car service are not an option. Servicing a battery in a workshop takes time and money. In addition, on a discharged battery, you still need to get to the service. Anyone who knows how to use a soldering iron can assemble a workable charger for a car battery with their own hands.

Some battery theory

Any accumulator (battery) is a store of electrical energy. When voltage is applied to it, energy accumulates due to chemical changes inside the battery. When the consumer is connected, the opposite process occurs: the reverse chemical change creates voltage at the terminals of the device, current flows through the load. Thus, in order to receive voltage from the battery, it must first be “put”, i.e., charge the battery.

Almost any car has its own generator, which, when the engine is running, provides power to on-board equipment and charges the battery, replenishing the energy spent on starting the engine. But in some cases (frequent or heavy starting of the engine, short trips, etc.), the battery energy does not have time to recover, the battery gradually discharges. There is only one way out of this situation - charging with an external charger.

How to check battery status

To decide on the need for charging, you need to determine the state of the battery. The simplest option - "twists / does not twist" - at the same time is unsuccessful. If the battery "does not turn", for example, in the morning in the garage, then you will not go anywhere at all. The “not spinning” condition is critical, and the consequences for the battery can be sad.

The best and most reliable method for checking the condition of a battery is to measure the voltage on it with a conventional tester. At an air temperature of about 20 degrees dependence of the degree of charge on the voltage on the terminals of a disconnected from the load (!) battery is as follows:

• 12.6…12.7 V - fully charged;
• 12.3…12.4 V - 75%;
• 12.0…12.1 V - 50%;
• 11.8…11.9 V - 25%;
• 11.6 ... 11.7 V - discharged;
• below 11.6 V - deep discharge.

It should be noted that the voltage of 10.6 volts is critical. If it drops below, then the "car battery" (especially maintenance-free) will fail.

Proper charging

There are two methods of charging a car battery - constant voltage and constant current. Everyone has their own features and disadvantages:

Homemade battery chargers

Assembling a charger for a car battery with your own hands is real and not very difficult. To do this, you need to have basic knowledge of electrical engineering and be able to hold a soldering iron in your hands.

A simple device for 6 and 12 V

Such a scheme is the most elementary and budgetary. With this charger, you can charge any lead-acid battery with an operating voltage of 12 or 6 V and an electric capacity of 10 to 120 A/h.

The device consists of a step-down transformer T1 and a powerful rectifier assembled on diodes VD2-VD5. The charging current is set by switches S2-S5, with the help of which quenching capacitors C1-C4 are connected to the power supply circuit of the primary winding of the transformer. Due to the multiple "weight" of each switch, various combinations allow you to stepwise adjust the charging current within 1-15 A in 1 A increments. This is enough to select the optimal charging current.

For example, if a current of 5 A is needed, then you will need to turn on the toggle switches S4 and S2. Closed S5, S3 and S2 will give a total of 11 A. A voltmeter PU1 is used to control the voltage on the battery, the charging current is monitored using an ammeter PA1.

In the design, you can use any power transformer with a power of about 300 W, including a home-made one. It should produce a voltage of 22–24 V at a current of up to 10–15 A on the secondary winding. In place of VD2-VD5, any rectifier diodes that can withstand a forward current of at least 10 A and a reverse voltage of at least 40 V will do. D214 or D242 will do. They should be installed through insulating gaskets on a radiator with a scattering area of ​​​​at least 300 cm2.

Capacitors C2-C5 must be non-polar paper with an operating voltage of at least 300 V. For example, MBCHG, KBG-MN, MBGO, MBGP, MBM, MBGCH are suitable. Similar cube-shaped capacitors were widely used as phase-shifters for electric motors in household appliances. As PU1, a DC voltmeter of the M5-2 type with a measurement limit of 30 V was used. PA1 is an ammeter of the same type with a measurement limit of 30 A.

The circuit is simple, if you assemble it from serviceable parts, then it does not need to be adjusted. This device is also suitable for charging six-volt batteries, but the "weight" of each of the switches S2-S5 will be different. Therefore, you will have to navigate in the charging currents by the ammeter.

Continuously adjustable current

According to this scheme, it is more difficult to assemble a car battery charger with your own hands, but it can be repeated and also does not contain scarce parts. With its help, it is permissible to charge 12-volt batteries with a capacity of up to 120 A / h, the charge current is smoothly adjustable.

The battery is charged by a pulsed current, a thyristor is used as a regulating element. In addition to the smooth current adjustment knob, this design also has a mode switch, when turned on, the charging current is doubled.

The charging mode is controlled visually by the pointer device RA1. Resistor R1 is homemade, made of nichrome or copper wire with a diameter of at least 0.8 mm. It serves as a current limiter. Lamp EL1 - indicator. In its place, any small-sized indicator lamp with a voltage of 24-36 V will do.

A step-down transformer can be used ready-made with an output voltage through the secondary winding of 18–24 V at a current of up to 15 A. If there was no suitable device at hand, then you can make it yourself from any network transformer with a power of 250–300 W. To do this, all windings are wound from the transformer, except for the mains winding, and one secondary winding is wound with any insulated wire with a cross section of 6 mm. sq. The number of turns in the winding is 42.

Thyristor VD2 can be any of the KU202 series with letters V-N. It is installed on a radiator with a dissipation area of ​​at least 200 cm2. The power installation of the device is made with wires of minimum length and with a cross section of at least 4 mm. sq. In place of VD1, any rectifier diode with a reverse voltage of at least 20 V and a current of at least 200 mA will work.

Setting up the device comes down to calibrating the RA1 ammeter. This can be done by connecting several 12-volt lamps with a total power of up to 250 W instead of a battery, controlling the current using a known-good reference ammeter.

From a computer power supply

To assemble this simple charger with your own hands, you will need a regular power supply from an old ATX computer and knowledge of radio engineering. But on the other hand, the characteristics of the device will turn out to be decent. With its help, batteries are charged with a current of up to 10 A, adjusting the current and voltage of the charge. The only condition is that the PSU is desirable on the TL494 controller.

For creating do-it-yourself car charging from a computer power supply you will have to assemble the circuit shown in the figure.

Step-by-step operations necessary for finalization will look like this:

1. Bite off all the wires of the power buses, except for the yellow and black ones.
2. Connect the yellow and black wires separately - these will be the “+” and “-” memory, respectively (see diagram).
3. Cut all traces leading to pins 1, 14, 15 and 16 of the TL494 controller.
4. Install variable resistors with a nominal value of 10 and 4.4 kOhm on the casing of the power supply unit - these are the voltage and current adjustment bodies, respectively.
5. Hinged mounting to assemble the circuit shown in the figure above.

If the installation is done correctly, then the revision is completed. It remains to equip the new charger with a voltmeter, ammeter and wires with "crocodiles" for connecting to the battery.

It is possible to use any variable and fixed resistors in the design, except for the current one (the lower one according to the circuit with a nominal value of 0.1 Ohm). Its power dissipation is at least 10 watts. You can make such a resistor yourself from a nichrome or copper wire of the appropriate length, but you can actually find a ready-made one, for example, a shunt from a Chinese digital tester for 10 A or a C5-16MV resistor. Another option is two 5WR2J resistors connected in parallel. Such resistors are in switching power supplies for PCs or TVs.

What you need to know when charging a battery

When charging a car battery, it is important to follow a number of rules. This will help you prolong battery life and keep your health:

The question of creating a simple do-it-yourself battery charger has been clarified. Everything is quite simple, it remains to stock up on the necessary tools and you can safely get to work.

Now it makes no sense to assemble a charger for car batteries on your own: there is a huge selection of ready-made devices in stores, their prices are reasonable. However, let's not forget that it's nice to do something useful with your own hands, especially since a simple car battery charger can be assembled from improvised parts, and its price will be a penny.

The only thing to immediately warn about is that circuits without precise adjustment of the current and output voltage, which do not have a current cutoff at the end of the charge, are suitable for charging only lead-acid batteries. For AGM and the use of such chargers damages the battery!

How to make a simple transformer device

The circuit of this charger from a transformer is primitive, but workable and is assembled from available parts - factory chargers of the simplest type are designed in the same way.

At its core, this is a full-wave rectifier, hence the requirements for the transformer: since the voltage at the output of such rectifiers is equal to the nominal AC voltage times the root of two, then at 10V on the transformer winding we will get 14.1 V at the charger output. Any diode bridge is taken with a direct current of more than 5 amperes or it can be assembled from four separate diodes, and a measuring ammeter is selected with the same current requirements. The main thing is to place it on a radiator, which in the simplest case is an aluminum plate with an area of ​​at least 25 cm2.

The primitiveness of such a device is not only a minus: due to the fact that it has neither adjustment nor automatic shutdown, it can be used to “resuscitate” sulfated batteries. But we must not forget about the lack of protection against polarity reversal in this circuit.

The main problem is where to find a transformer of suitable power (at least 60 W) and with a given voltage. Can be used if a Soviet incandescent transformer turns up. However, its output windings have a voltage of 6.3V, so you will have to connect two in series, unwinding one of them so that you get a total of 10V at the output. An inexpensive transformer TP207-3 is suitable, in which the secondary windings are connected as follows:

At the same time, we unwind the winding between terminals 7-8.

Simple electronic charger

However, you can do without rewinding by supplementing the circuit with an electronic output voltage regulator. In addition, such a scheme will be more convenient in garage applications, as it will allow you to adjust the charge current during supply voltage drops, it is also used for small-capacity car batteries if necessary.

The role of the regulator here is performed by the composite transistor KT837-KT814, the variable resistor regulates the current at the output of the device. When assembling the charge, the 1N754A zener diode can be replaced with the Soviet D814A.

The circuit of the regulated charger is simple to repeat, and is easily assembled by surface mounting without the need for PCB etching. However, keep in mind that field-effect transistors are placed on a radiator, the heating of which will be noticeable. It is more convenient to use an old computer cooler by connecting its fan to the charger outlets. Resistor R1 must have a power of at least 5 W, it is easier to wind it from nichrome or fechral on your own or connect 10 one-watt resistors of 10 ohms in parallel. You can not put it, but we must not forget that it protects the transistors in the event of a short circuit.

When choosing a transformer, focus on the output voltage of 12.6-16V, take either an incandescent transformer by connecting two windings in series, or select a ready-made model with the desired voltage.

Video: The simplest battery charger

Alteration of the charger from the laptop

However, you can do without searching for a transformer if you have an unnecessary laptop charger at hand - with a simple alteration, we will get a compact and lightweight switching power supply that can charge car batteries. Since we need to get a voltage at the output of 14.1-14.3 V, no ready-made power supply will work, but the conversion is simple.
Let's look at a section of a typical scheme, according to which devices of this kind are assembled:

In them, maintaining a stabilized voltage is carried out by a circuit from a TL431 microcircuit that controls an optocoupler (not shown in the diagram): as soon as the output voltage exceeds the value set by resistors R13 and R12, the microcircuit lights up the optocoupler LED, informs the PWM controller of the converter a signal to reduce the duty cycle of the supplied to the pulse transformer. Hard? In fact, everything is easy to make with your own hands.

Having opened the charger, we find not far from the TL431 output connector and two resistors connected to the Ref leg. It is more convenient to adjust the upper arm of the divider (in the diagram - resistor R13): by reducing the resistance, we reduce the voltage at the output of the charger, increasing it - we raise it. If we have a 12 V charger, we need a resistor with a large resistance, if the charger is 19 V, then with a smaller one.

Video: Charging for car batteries. Protection against short circuit and polarity reversal. DIY

We solder the resistor and instead install a trimmer, pre-configured by the multimeter for the same resistance. Then, having connected a load (a light bulb from a headlight) to the output of the charger, we turn it on and smoothly rotate the trimmer engine, while simultaneously controlling the voltage. As soon as we get a voltage in the range of 14.1-14.3 V, we turn off the memory from the network, fix the trimming resistor engine with varnish (at least for nails) and assemble the case back. It will take no more time than you spent reading this article.

There are also more complex stabilization schemes, and they can already be found in Chinese blocks. For example, here the optocoupler is controlled by the TEA1761 chip:

However, the setting principle is the same: the resistance of the resistor soldered between the positive output of the power supply and the 6th leg of the microcircuit changes. In the above diagram, two parallel resistors are used for this (thus, a resistance that is out of the standard series is obtained). We also need to solder a trimmer instead of them and adjust the output to the desired voltage. Here is an example of one of these boards:

By dialing, you can understand that we are interested in a single resistor R32 on this board (circled in red) - we need to solder it.

Similar recommendations are often found on the Internet on how to make a homemade charger from a computer power supply. But keep in mind that all of them are essentially reprints of old articles from the beginning of the 2000s, and such recommendations are not applicable to more or less modern power supplies. It is no longer possible to simply raise the 12 V voltage to the desired value in them, since other output voltages are also controlled, and they will inevitably “float away” with this setting, and the power supply protection will work. You can use laptop chargers that produce a single output voltage, they are much more convenient for rework.

You will need

• Power transformer TS-180-2, wires with a cross section of 2.5 mm2, four diodes D242A, mains plug, soldering iron, solder, fuses 0.5A and 10A;
• household light bulb up to 200 W;
• a semiconductor diode that conducts electricity in only one direction. As such a diode, you can use charging from a laptop.

Instruction

A simple charger can be made from an old computer power supply. Since it needs a current of 10% of the entire battery capacity, any power supply with a power of more than 150 volts can be an effective source of charge. Almost all power supplies have a PWM controller on a TL494 chip (or similar KA7500). First of all, you need to unsolder the extra wires (from -5V, -12V, +5V, +12V sources). Then remove R1 and replace it with a tuning resistor with the highest value of 27 kOhm. The sixteenth conclusion is also disconnected from the main wire, the fourteenth and fifteenth are cut at the junction.

On the rear plate of the block, you need to install a potentiometer-current regulator R10. There are also 2 cords: one for the network, the other for the battery terminals.

Now we need to deal with conclusions 1, 14,15 and 16. First they need to be irradiated. To do this, the wire is cleaned of insulation and cauterized with a soldering iron. This will remove the oxide film, after which the wire is applied to a piece of rosin, and then pressed again with a soldering iron. The wire should turn yellow-brown. Now you need to attach it to a piece of solder and for the third, last time, press it with a soldering iron. The wire should turn silver. After the end of this procedure, it remains to solder the stranded thin wires.

Idling must be set with a variable resistor at the middle position of the potentiometer R10. The open circuit voltage will set the full charge in the range from 13.8 to 14.2 volts. Clamps are installed on the ends of the terminals. It is better to make insulating tubes multi-colored so as not to get tangled in the wires. This may damage the instrument. Red usually refers to "plus" and black to "minus".

If the device will only be used to charge the battery, you can do without a voltmeter and ammeter. It will be enough to use the graduated scale of the R10 potentiometer with a value of 5.5-6.5 amperes. The charging process from such a device should be easy, automatic and do not require your additional efforts. This charger virtually eliminates the possibility of overheating or overcharging the battery.

Another way to manufacture a car battery is based on the use of an adapted twelve-volt adapter. It does not require a car battery charger. It is important to remember that the voltage of the battery and the voltage of the power supply must be equal, otherwise the charger will be useless.

First you need to cut and expose up to 5 cm the end of the adapter wire. Then the opposite wires are separated by 40 cm. Now you need to put on a crocodile clip on each of the wires. Don't forget to take the colored clips so you don't mix up the polarities. It is necessary to connect each clip to the battery in series, following the principle "from plus to plus" and "from minus to minus". Now it remains to turn on the adapter. This method is quite simple, the only difficulty is in choosing the right power source. Such a battery can overheat during the charging process, so it is important to monitor it and interrupt it for a while in case of overheating.

A car battery charger can be made from an ordinary light bulb and a diode. Such a device will be very simple and you need very few initial elements: a light bulb, a semiconductor diode, wires with terminals and a plug. The light bulb should be up to 200 volts. The higher its power, the faster the charging process will be. A semiconductor diode should only conduct electricity in one direction. You can take, for example, charging from a laptop.

The light bulb should burn at half heat, but if it does not burn at all, you need to refine the circuit. It is possible that the light will turn off when the car battery is fully charged, but this is unlikely. Charging with such a device will take about 10 hours. Then be sure to disconnect it from the network, otherwise overheating is inevitable, which will disable the battery.

If the situation is urgent, and there is no time to build more complex chargers, you can charge the battery with a powerful diode and a heater using mains current. You need to connect to the network in the following sequence: a diode, then a heater, then a battery. This method is inefficient, because it takes a lot of electricity, and the efficiency is only 1%. Therefore, this charger is the most unreliable, but also the easiest to manufacture.

In order to make the simplest charger, considerable effort and effort will be required. technical knowledge. It is better to always have a reliable factory charger on hand, but if necessary and with sufficient technical skills, you can do it yourself.

Even with a fully serviceable car, sooner or later a situation may arise when it is required from an external source - a long parking lot, side lights accidentally left on, and so on. The owners of old equipment, on the other hand, are well aware of the need for regular recharging of the battery - this is due to the self-discharge of a "tired" battery, and increased leakage currents in electrical circuits, primarily in the diode bridge of the generator.

You can purchase a ready-made charger: they available in a variety of options and easily accessible. But it may seem to someone that it will be more interesting to make a charger for a car battery with your own hands, and for someone the opportunity to make a charger literally from improvised material will help out.

Semiconductor diode + light bulb

It is not known who first came up with the idea to charge the battery in this way, but this is exactly the case when you can charge the battery literally by hand. In this circuit, the current source is electrical network 220V, the diode is needed to convert AC to pulsating DC, and the light bulb serves as a current-limiting resistor.

The calculation of this charger is as simple as its circuit:

• The current flowing through the lamp is determined based on its power as I=P/U, where U- network voltage, P- lamp power. That is, for a lamp of 60 W, the current in the circuit will be 0.27 A.
• Since the diode cuts off every second half-wave of the sinusoid, the real average load current will be, taking this into account, equal to 0.318*I.