The simplest homemade charger for a car battery. DIY car battery charger. A similar manufacturing option is shown in the video

Very often, especially in the cold season, car enthusiasts are faced with the need to charge a car battery. It is possible, and advisable, to purchase a factory charger, preferably a charging and starting charger for use in the garage.

But, if you have electrical engineering skills and certain knowledge in the field of radio engineering, then you can make a simple charger for a car battery with your own hands. In addition, it is better to prepare in advance for possible case when the battery suddenly discharges away from home or a parking and maintenance site.

General information about the battery charging process

Charging a car battery is necessary when the voltage drop across the terminals is less than 11.2 Volts. Despite the fact that the battery can start the car engine even with such a charge, during long-term parking at low voltages, plate sulfation processes begin, which lead to loss of battery capacity.

Therefore, when wintering a car in a parking lot or garage, it is necessary to constantly recharge the battery and monitor the voltage at its terminals. A better option is to remove the battery, put it in a warm place, but still remember to maintain its charge.

The battery is charged using constant or pulsed current. In the case of charging from a constant voltage source, a charge current equal to one tenth of the battery capacity is usually selected.

For example, if the capacity battery is 60 ampere-hours, the charging current should be selected at 6 amperes. However, research shows that the lower the charge current, the less intense the sulfation processes.

Moreover, there are methods for desulfating battery plates. They are as follows. First, the battery is discharged to a voltage of 3–5 Volts with high currents of short duration. For example, such as when turning on the starter. Then there is a slow full charge with a current of about 1 Ampere. Such procedures are repeated 7-10 times. There is a desulfation effect from these actions.

Desulfating pulse chargers are practically based on this principle. The battery in such devices is charged with pulsed current. During the charging period (several milliseconds), a short discharge pulse of reverse polarity and a longer charging pulse of direct polarity are applied to the battery terminals.

It is very important during the charging process to prevent the effect of overcharging the battery, that is, the moment when it is charged to the maximum voltage (12.8 - 13.2 Volts, depending on the type of battery).

This can cause an increase in the density and concentration of the electrolyte, irreversible destruction of the plates. That is why factory chargers are equipped with an electronic control and shutdown system.

Schemes of homemade simple chargers for a car battery

Protozoa

Let's consider the case of how to charge a battery using improvised means. For example, a situation when you left your car near your house in the evening, forgetting to turn off some electrical equipment. By morning the battery was discharged and would not start the car.

In this case, if your car starts well (with half a turn), it is enough to “tighten” the battery a little. How to do this? First, you need a constant voltage source ranging from 12 to 25 volts. Secondly, restrictive resistance.

What can you recommend?

Nowadays, almost every home has a laptop. The power supply of a laptop or netbook, as a rule, has an output voltage of 19 Volts and a current of at least 2 amperes. The external pin of the power connector is minus, the internal pin is positive.

As a limiting resistance, and it is mandatory!!!, you can use the car's interior light bulb. You can, of course, have more power from turn signals or even worse stops or dimensions, but there is a possibility of overloading the power supply. The simplest circuit is assembled: minus the power supply - light bulb - minus the battery - plus the battery - plus the power supply. In a couple of hours the battery will be charged enough to start the engine.

If you don’t have a laptop, you can pre-purchase a powerful rectifier diode on the radio market with a reverse voltage of more than 1000 Volts and a current of 3 Amperes. He has small sizes, you can put it in the glove compartment for an emergency.

What to do in an emergency?

Conventional lamps can be used as a limiting load incandescent at 220 Volt. For example, a 100 Watt lamp (power = voltage X current). Thus, when using a 100-watt lamp, the charge current will be about 0.5 Ampere. Not much, but overnight it will give 5 Amp-hours of capacity to the battery. Usually it is enough to crank the car starter a couple of times in the morning.

If you connect three 100-watt lamps in parallel, the charging current will triple. You can charge your car battery almost halfway overnight. Sometimes they turn on an electric stove instead of lamps. But here the diode may already fail, and at the same time the battery.

In general, this kind of experiments with direct charging of the battery from a 220 Volt alternating voltage network extremely dangerous. They should only be used in extreme cases when there is no other option.

From computer power supplies

Before you start making your own charger for a car battery, you should evaluate your knowledge and experience in the field of electrical and radio engineering. In accordance with this, select the complexity level of the device.

First of all, you should decide on the element base. Very often, computer users end up with old system units. There are power supplies there. Along with the +5V supply voltage, they contain a +12 Volt bus. As a rule, it is designed for current up to 2 Amperes. This is quite enough for a weak charger.

Video - step-by-step manufacturing instructions and a diagram of a simple charger for a car battery from computer unit power supply:

But 12 volts is not enough. It is necessary to “overclock” it to 15. How? Usually using the "poke" method. Take a resistance of about 1 kiloOhm and connect it in parallel with other resistances near the microcircuit with 8 legs in the secondary circuit of the power supply.

Thus, the transmission coefficient of the feedback circuit changes, respectively, and the output voltage.

It’s difficult to explain in words, but usually users succeed. By selecting the resistance value, you can achieve an output voltage of about 13.5 Volts. This is enough to charge a car battery.

If you don’t have a power supply at hand, you can look for a transformer with a secondary winding of 12 - 18 Volts. They were used in old tube televisions and other household appliances.

Now such transformers can be found in waste sources uninterruptible power supply, you can buy it for pennies on the secondary market. Next, we begin manufacturing the transformer charger.

Transformer chargers

Transformer chargers are the most common and safe devices, widely used in automotive practice.

Video - a simple charger for a car battery using a transformer:

The most simple circuit transformer charger for a car battery contains:

network transformer;
rectifier bridge;
restrictive load.

A large current flows through the limiting load and it gets very hot, so to limit the charging current, capacitors are often used in the primary circuit of the transformer.

In principle, in such a circuit you can do without a transformer if you choose the capacitor wisely. But without galvanic isolation from the network AC such a circuit will be dangerous from the point of view of electric shock.

More practical charger circuits for car batteries with regulation and limitation of charge current. One of these schemes is shown in the figure:

You can use the rectifier bridge of a faulty car generator as powerful rectifier diodes by slightly reconnecting the circuit.

More complex pulse chargers with desulfation function are usually made using microcircuits, even microprocessors. They are difficult to manufacture and require special installation and configuration skills. In this case, it is easier to purchase a factory device.

Security requirements

Conditions that must be met when using a homemade car battery charger:

The charger and battery must be located on a fireproof surface during charging;
when using simple chargers, you must use individual means protection (insulating gloves, rubber mat);
when using newly manufactured devices, constant monitoring of the charging process is necessary;
the main controlled parameters of the charging process are current, voltage at the battery terminals, temperature of the charger body and battery, control of the boiling point;
When charging at night, devices must be present protective shutdown(RCD) in the network connection.

Video - diagram of a charger for a car battery from a UPS:

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Comments on the article:

Lyokha

The information presented here is certainly interesting and informative. As a former radio engineer of the Soviet school, I read it with great interest. But in reality, now even “desperate” radio amateurs are unlikely to bother searching for circuit diagrams for a homemade charger and later assembling it with a soldering iron and radio components. Only radio fanatics will do this. It’s much easier to buy a factory-made device, especially since the prices, I think, are affordable. As a last resort, you can turn to other car enthusiasts with a request to “light up”, fortunately, now there are plenty of cars everywhere. What is written here is useful not so much for its practical value (although that too), but for instilling interest in radio engineering in general. After all, most modern children not only cannot distinguish a resistor from a transistor, but they won’t be able to pronounce it the first time. And this is very sad...

Michael

When the battery was old and half-dead, I often used a laptop power supply to recharge. As a current limiter I used an unnecessary old taillight with four 21-watt bulbs connected in parallel. I control the voltage at the terminals, at the beginning of charging it is usually about 13 V, the battery greedily eats up the charge, then the charging voltage increases, and when it reaches 15 V, I stop charging. It takes half an hour to an hour to reliably start the engine.

Ignat

I have a Soviet charger in my garage, it’s called “Volna”, made in ’79. Inside is a hefty and heavy transformer and several diodes, resistors and transistors. Almost 40 years in service, and this despite the fact that my father and brother use it constantly, not only for charging, but also as a 12 V power supply. But now it’s really easier to buy a cheap one Chinese device for five hundred square meters, rather than bother with a soldering iron. And on Aliexpress you can even buy it for one and a half hundred, although it will take a long time to send it. Although I liked the option from the computer power supply, I have a dozen old ones lying around in the garage, but they work quite well.

San Sanych

Hmmm. Of course, the Pepsicol generation is growing... :-\ The correct charger should produce 14.2 volts. No more and no less. With a greater potential difference, the electrolyte will boil, and the battery will swell so that it will then be difficult to remove it or, conversely, not to install it back in the car. With a smaller potential difference, the battery will not charge. The most normal circuit presented in the material is with a step-down transformer (first). In this case, the transformer must produce exactly 10 volts at a current of at least 2 amperes. There are plenty of these on sale. It is better to install domestic diodes - D246A (must be installed on a radiator with mica insulators). At worst - KD213A (these can be glued to an aluminum radiator with superglue). Any electrolytic capacitor with a capacity of at least 1000 uF for an operating voltage of at least 25 volts. A very large capacitor is also not needed, since due to the ripples of the under-rectified voltage we obtain the optimal charge for the battery. In total we get 10 * root of 2 = 14.2 volts. I myself have had such a charger since the days of the 412th Muscovite. Not killable at all. 🙂

Kirill

In principle, if you have the necessary transformer, it is not so difficult to assemble a transformer charger circuit yourself. Even for me, not a very big specialist in the field of radio electronics. Many people say, why bother if it’s easier to buy. I agree, but it’s not about the final result, but about the process itself, because it’s much more pleasant to use a manufactured thing with my own hands than purchased. And most importantly, if this homemade product breaks down, then the one who assembled it knows his battery charger thoroughly and is able to fix it quickly. And if a purchased product burns out, then you still need to dig around and it’s not at all a fact that a breakdown will be found. I vote for self-built devices!

Oleg

In general I think that ideal option- this is a charger industrial production, that’s why I have this and carry it in my trunk all the time. But in life situations are different. Once I was visiting my daughter in Montenegro, and there they generally don’t carry anything with them and rarely do anyone even have one. So she forgot to close the door at night. The battery is drained. No diode at hand, no computer. I found a Boschevsky screwdriver with 18 volts and 1 ampere current. So I used his charger. True, I charged it all night and periodically checked for overheating. But she couldn’t stand it, in the morning they started her with half a kick. So there are many options, you have to look. Well, regarding homemade chargers, as a radio engineer I can only recommend transformer ones, i.e. isolated via the network, they are safe compared to capacitors, diodes with a light bulb.

Sergey

Charging the battery with non-standard devices can lead to either complete irreversible wear or a decrease in guaranteed operation. The whole problem is connecting homemade products, so that the rated voltage does not exceed the permissible one. It is necessary to take into account temperature differences and this is very important point, especially in winter time. When we decrease by a degree, we increase it and vice versa. There is an approximate table depending on the type of battery - it is not difficult to remember. Another important point is that all measurements of voltage and, of course, density are made only when the engine is cold, with the engine not running.

Vitalik

In general, I use the charger extremely rarely, maybe once every two or three years, and only when I go away for a long time, for example in the summer for a couple of months to the south to visit relatives. And so basically the car is in operation almost every day, the battery is charged and there is no need for such devices. Therefore, I think that buying for money something that you practically never use is not very smart. The best option- assemble such a simple craft, say, from a computer power supply, and let it lie around, waiting in the wings. After all, the main thing here is not to fully charge the battery, but to cheer it up a little to start the engine, and then the generator will do its job.

Nikolay

Just yesterday we recharged the battery using a screwdriver charger. The car was parked outside, the frost was -28, the battery was spun a couple of times and stopped. We took out a screwdriver, a couple of wires, connected it, and after half an hour the car started up safely.

Dmitry

A ready-made store charger is of course an ideal option, but who wants to use their own hands, and considering that you don’t have to use it often, you don’t have to spend money on the purchase and do the charging yourself.
A homemade charger should be autonomous, not require supervision or current control, since we charge most often at night. In addition, it must provide a voltage of 14.4 V and ensure that the battery is turned off when the current and voltage exceed the norm. It should also provide protection against polarity reversal.
The main mistakes that “Kulibins” make are connecting directly to a household electrical network, this is not even a mistake, but a violation of safety regulations, the next limiting the charging current is by capacitors, and it’s also more expensive: one bank of capacitors 32 uF at 350-400 V (less than that is not possible) will cost like a cool branded charger.
The easiest way is to use a computer pulse block power supply (UPS), it is now more accessible than a transformer on hardware, and there is no need to do separate protection, everything is ready.
If you don't have a computer power supply, you need to look for a transformer. A power supply with filament windings from old tube TVs - TS-130, TS-180, TS-220, TS-270 - is suitable. They have plenty of power behind their eyes. You can find an old TN filament transformer at the car market.
But all this is only for those who are friends with electricians. If not, don’t bother - you won’t do the exercises that meet all the requirements, so buy ready-made ones and don’t waste time.

Laura

I got a charger from my grandfather. Since Soviet times. Homemade. I don’t understand this at all, but when my friends see it, they click their tongues in admiration and respect, saying, this is a thing “for centuries.” They say it was assembled using some lamps and still works. True, I practically don’t use it, but that’s not the point. Everyone criticizes Soviet technology, but it turns out to be many times more reliable than modern technology, even homemade ones.

Vladislav

In general, a useful thing in the household, especially if there is a function for adjusting the output voltage

Alexey

I’ve never had the opportunity to use or assemble homemade chargers, but I can quite imagine the principle of assembly and operation. I think that homemade products are no worse than factory ones, it’s just that no one wants to tinker, especially since the prices for store-bought ones are quite affordable.

Victor

In general, the schemes are simple, there are few parts and they are accessible. Adjustment can also be done if you have some experience. So it's quite possible to collect. Of course, it is very pleasant to use a device assembled with your own hands)).

Ivan

The charger is, of course, a useful thing, but now there are more interesting specimens on the market - their name is start-chargers

Sergey

There are a lot of charger circuits and as a radio engineer I have tried many of them. Until last year, I had a scheme that worked for me since Soviet times and it worked perfectly. But one day (through my fault) the battery completely died in the garage and I needed a cyclic mode to restore it. Then I didn’t bother (due to lack of time) with creating new scheme, but just went and bought it. And now I carry a charger in the trunk just in case.

Car owners often face a problem battery discharge. If this happens far from service stations, auto shops and gas stations, you can independently make a device for charging the battery from available parts. Let's look at how to make a charger for a car battery with your own hands, having minimal electrical knowledge. installation work.

This device is best used only in critical situations. However, if you are familiar with electrical engineering, electrical and fire safety rules, and have skills in electrical measurements and installation work, a homemade charger can easily replace the factory unit.

Causes and signs of battery discharge

During the operation of the battery, when the engine is running, the battery is constantly recharged from the vehicle's generator. You can check the charging process by connecting a multimeter to the battery terminals with the engine running, measuring the charging voltage of the car battery. The charge is considered normal if the voltage at the terminals is from 13.5 to 14.5 Volts.

To fully charge, you need to drive the car for at least 30 kilometers, or about half an hour in city traffic.

The voltage of a normally charged battery during parking should be at least 12.5 Volts. If the voltage is less than 11.5 Volts, the car engine may not start during the start. Reasons for battery discharge:

The battery has significant wear ( more than 5 years of operation);
improper operation of the battery, leading to sulfation of the plates;
long-term parking vehicle, especially in the cold season;
the urban rhythm of car driving with frequent stops when the battery does not have time to charge sufficiently;
leaving the car's electrical appliances on while parked;
damage to the electrical wiring and equipment of the vehicle;
leaks in electrical circuits.

Many car owners do not have the means to measure battery voltage in their on-board tool kit ( voltmeter, multimeter, probe, scanner). In this case, you can be guided by indirect signs of battery discharge:

dim lights on the dashboard when the ignition is turned on;
lack of starter rotation when starting the engine;
loud clicks in the starter area, lights on the dashboard going out when starting;
complete lack of reaction from the car when the ignition is turned on.

If the above symptoms appear, first of all you need to check the battery terminals, clean and tighten them if necessary. During the cold season, you can try placing the battery in the warm room and warm it up.

You can try to “light” the car from another car. If these methods do not help or are not possible, you have to use a charger.

DIY universal charger. Video:

Operating principle

Most devices charge batteries with constant or pulsed currents. How many amps does it take to charge a car battery? The charge current is chosen equal to one tenth of the battery capacity. With a capacity of 100 Ah, the charging current of a car battery will be 10 Amperes. The battery will have to be charged for about 10 hours until it is fully charged.

Charging a car battery with high currents can lead to the sulfation process. To avoid this, it is better to charge the battery with low currents, but for a longer time.

Pulse devices significantly reduce the effect of sulfation. Some pulse chargers have a desulfation mode, which allows you to restore battery functionality. It consists of sequential charge-discharge with pulsed currents according to a special algorithm.

When charging the battery, do not allow it to overcharge. It can lead to boiling of the electrolyte and sulfation of the plates. It is necessary that the device has its own control system, parameter measurement and emergency shutdown.

Since the 2000s, they began to install on cars special types batteries: AGM and gel. Charging a car battery of these types differs from the normal mode.

As a rule, it is three-stage. Up to a certain level, the charge occurs with a large current. Then the current decreases. The final charge occurs with even smaller pulse currents.

Charging a car battery at home

Often in driving practice a situation arises when, having parked the car near the house in the evening, in the morning it is discovered that the battery is discharged. What can be done in such a situation when there is no soldering iron at hand, no parts, but you need to start it?

Usually the battery has a small capacity left; it just needs to be “tightened up” a little so that there is enough charge to start the engine. In this case, a power supply from some household or office equipment, for example, a laptop, can help.

Charging from a laptop power supply

The voltage produced by the laptop power supply is usually 19 Volts, the current is up to 10 Amps. This is enough to charge the battery. But you CANNOT connect the power supply directly to the battery. It is necessary to include a limiting resistance in series in the charging circuit. You can use a car light bulb as it, better for interior lighting. It can be purchased at your nearest gas station.

Typically the middle pin of the connector is positive. A light bulb is connected to it. The + battery is connected to the second terminal of the light bulb.

The negative terminal is connected to the negative terminal of the power supply. The power supply usually has a label indicating the polarity of the connector. A couple of hours of charging using this method is enough to start the engine.

Circuit diagram of a simple charger for a car battery.

Charge from a household network

A more extreme charging method is directly from household network. It is used only in critical situations, using maximum electrical safety measures. To do this you will need a lighting lamp ( not energy saving).

You can use an electric stove instead. You also need to purchase a rectifier diode. Such a diode can be “borrowed” from a faulty energy-saving lamp. During this time, it is better to turn off the voltage supplied to the apartment. The diagram is shown in the figure.

The charging current with a lamp power of 100 Watts will be approximately 0.5 A. Overnight the battery will be recharged for only a few ampere-hours, but this may be enough to start. If you connect three lamps in parallel, the battery will be charged three times more. If you connect an electric stove instead of a light bulb ( at the lowest power), then the charging time will be significantly reduced, but this is very dangerous. In addition, the diode may break through, then the battery may short out. Charging methods from 220 V are dangerous.

DIY car battery charger. Video:

Homemade car battery charger

Before making a charger for a car battery, you should evaluate your experience electrical installation work, knowledge of electrical engineering, based on this, proceed to choosing a charger circuit for a car battery.

You can look in the garage to see if there are old devices or units. A power supply from an old computer is suitable for the device. It has almost everything:

220 V connector;
power switch;
electrical circuit;
cooling fan;
connection terminals.

The voltages on it are standard: +5 V, -12 V and +12 Volts. To charge the battery, it is better to use a +12 Volt, 2 Ampere wire. The output voltage must be raised to the level of +14.5 - +15.0 Volts. This can usually be done by changing the resistance value in the feedback circuit ( about 1 kiloohm).

There is no need to install a limiting resistance, electronic circuit will independently regulate the charging current within 2 Amperes. It is easy to calculate that it will take about a day to fully charge a 50 A*h battery. Appearance devices.

You can pick up or buy at a flea market a network transformer with a secondary winding voltage from 15 to 30 Volts. These were used in old TVs.

Transformer devices

The simplest circuit diagram of a device with a transformer.

Its disadvantage is the need to limit the current in the output circuit and the associated large power losses and heating of the resistors. Therefore, capacitors are used to regulate the current.

Theoretically, having calculated the capacitor rating, you can not use power transformer, as shown in the diagram.

When purchasing capacitors, you should choose the appropriate rating with a voltage of 400 V or more.

In practice, devices with current regulation have become more widely used.

You can choose pulse homemade charger circuits for a car battery. They are more complex in circuit design and require certain installation skills. Therefore, if you do not have special skills, it is better to buy a factory unit.

Pulse chargers

Pulse chargers have a number of advantages:

Operating principle pulse devices is based on converting alternating voltage from a household electrical network to direct voltage using a VD8 diode assembly. The DC voltage is then converted into pulses of high frequency and amplitude. Pulse transformer T1 again converts the signal into DC voltage, which charges the battery.

Since the reverse conversion is carried out at a high frequency, the dimensions of the transformer are much smaller. The feedback necessary to control the charge parameters is provided by optocoupler U1.

Despite the apparent complexity of the device, when correct assembly the unit starts working without additional adjustment. This device provides a charging current of up to 10 Amps.

When charging the battery using homemade device necessary:

place the device and battery on a non-conductive surface;
comply with electrical safety requirements ( use gloves, a rubber mat, and tools with an electrical insulating coating);
Do not leave the charger turned on for a long time without control, monitor the voltage and temperature of the battery, and the charging current.

!
Today we will look at 3 simple charger circuits that can be used to charge a wide variety of batteries.

The first 2 circuits operate in linear mode, and linear mode primarily means high heat. But the charger is a stationary thing, and not portable, so that efficiency is a decisive factor, so the only disadvantage of the presented circuits is that they need a large cooling radiator, but otherwise everything is fine. Such schemes have always been used and will be used, as they have undeniable advantages: simplicity, low cost, do not “crap” the network (as in the case of pulsed circuits) and high repeatability.

Let's look at the first diagram:

This circuit consists of just a pair of resistors (with the help of which the end of charge voltage or the output voltage of the circuit as a whole is set) and a current sensor that sets the maximum output current of the circuit.

If you need a universal charger, the circuit will look like this:

By rotating the trimming resistor, you can set any output voltage from 3 to 30 V. In theory, up to 37V is possible, but in this case, 40V must be supplied to the input, which the author (AKA KASYAN) does not recommend doing. The maximum output current depends on the resistance of the current sensor and cannot be higher than 1.5A. The output current of the circuit can be calculated using the following formula:

Where 1.25 is the voltage of the reference source of the lm317 microcircuit, Rs is the resistance of the current sensor. To obtain a maximum current of 1.5A, the resistance of this resistor should be 0.8 Ohm, but in the circuit it is 0.2 Ohm.

The fact is that even without a resistor, the maximum current at the output of the microcircuit will be limited to the specified value; the resistor here is mostly for insurance, and its resistance is reduced to minimize losses. The greater the resistance, the more the voltage across it will drop, and this will lead to strong heating of the resistor.

The microcircuit must be installed on a massive radiator; an unstabilized voltage of up to 30-35V is supplied to the input, this is slightly less than the maximum permissible input voltage for the lm317 microcircuit. It must be remembered that the lm317 chip can dissipate a maximum of 15-20W of power, be sure to take this into account. You also need to take into account that the maximum output voltage of the circuit will be 2-3 volts less than the input.

Charging occurs at a stable voltage, and the current cannot exceed the set threshold. This circuit can even be used to charge lithium-ion batteries. If there is a short circuit at the output, nothing bad will happen, the current will simply be limited, and if the cooling of the microcircuit is good and the difference between the input and output voltages is small, the circuit can operate in this mode for an infinitely long time.

Everything is assembled on a small printed circuit board.

You can find it, as well as the printed circuit boards for the two subsequent circuits, along with the general archive of the project.

Second scheme is a powerful stabilized power supply with a maximum output current of up to 10A, it was built on the basis of the first option.

It differs from the first circuit in that an additional direct conduction power transistor is added here.

The maximum output current of the circuit depends on the resistance of the current sensors and the collector current of the transistor used. In this case, the current is limited to 7A.

The output voltage of the circuit is adjustable in the range from 3 to 30V, which will allow you to charge almost any battery. The output voltage is regulated using the same trimming resistor.

This option is great for charging car batteries; the maximum charge current with the components indicated in the diagram is 10A.

Now let's look at the principle of operation of the circuit. At low current values, the power transistor is closed. As the output current increases, the voltage drop across the specified resistor becomes sufficient and the transistor begins to open, and all the current will flow through the open junction of the transistor.

Naturally, due to the linear operating mode, the circuit will heat up, the power transistor and current sensors will heat up especially harshly. A transistor with an lm317 chip is screwed onto a common massive aluminum radiator. There is no need to insulate the heat sink substrates, since they are common.

It is highly desirable and even mandatory to use an additional fan if the circuit will be operated at high currents.
To charge batteries, you need to set the end-of-charge voltage by rotating the trimming resistor and that’s it. The maximum charging current is limited to 10 amperes; as the batteries charge, the current will drop. Scheme short circuits Don't be afraid, in case of a short circuit the current will be limited. As in the case of the first scheme, if there is good cooling, the device will be able to tolerate this operating mode for a long time.
Well, now some tests:

As you can see, the stabilization is working, so everything is fine. And finally third scheme:

It is a system automatic shutdown battery when fully charged, that is, it is not really a charger. The initial circuit underwent some modifications, and the board was refined during testing.

Let's look at the diagram.

As you can see, it is painfully simple, it contains only 1 transistor, an electromagnetic relay and small things. The author also has a diode bridge at the input and primitive protection against polarity reversal on the board; these components are not shown on the diagram.

The input of the circuit is supplied with constant voltage from the charger or any other power source.

It is important to note here that the charging current should not exceed the permissible current through the relay contacts and the fuse tripping current.

When power is supplied to the input of the circuit, the battery is charged. The circuit contains a voltage divider, which monitors the voltage directly on the battery.

As it charges, the voltage on the battery will increase. As soon as it becomes equal to the operating voltage of the circuit, which can be set by rotating the trimming resistor, the zener diode will operate, sending a signal to the base of the low-power transistor and it will operate.

Since an electromagnetic relay coil is connected to the collector circuit of the transistor, the latter will also work and the indicated contacts will open, and further power supply to the battery will stop, at the same time the second LED will work, notifying that charging is complete.

Homemade battery chargers usually have very simple design, and in addition, increased reliability precisely due to the simplicity of the circuit. Another advantage of making a charger yourself is the relative cheapness of the components and, as a result, the low cost of the device.

Why is a prefabricated structure better than a store-bought one?

The main task of such equipment is to maintain the charge of the car battery at the required level if necessary. If the battery discharge occurs near the house where there is the necessary device, then there will be no problems. Otherwise, when there is no suitable equipment to power the battery, and the funds are also insufficient, you can assemble the device yourself.

The need to use auxiliary means to recharge the car battery is primarily due to low temperatures in the cold season, when a half-discharged battery is a major, and sometimes completely unsolvable problem, unless the battery is recharged in time. Then homemade chargers for powering car batteries will become a salvation for users who do not plan to invest in such equipment, at least at the moment.

Operating principle

Up to a certain level, a car battery can receive power from the vehicle itself, or more precisely, from an electric generator. After this node, a relay is usually installed, responsible for setting the voltage to no more than 14.1V. A higher value is required for the battery to be fully charged. this parameter– 14.4V. Accordingly, batteries are used to implement such a task.

Main nodes of this device– transformer and rectifier. As a result, the output is D.C. with a voltage of a certain value (14.4V). But why is there a run-up with the voltage of the battery itself - 12V? This is done in order to ensure the ability to charge a battery that has been discharged to a level where the value of this battery parameter was equal to 12V. If charging is characterized by the same parameter value, then powering the battery will become a difficult task.

Watch the video, the simplest device for charging a battery:

But there is a nuance here: a slight excess of the battery voltage level is not critical, while a significantly increased value of this parameter will have a very bad effect on the performance of the battery in the future. The operating principle that distinguishes any, even the simplest car battery charger, is to increase the resistance level, which will lead to a decrease in the charging current.

Accordingly, than more value voltage (tends to 12V), the lower the current. For normal operation of the battery, it is advisable to set a certain amount of charge current (about 10% of the capacity). In a hurry, it is tempting to change the value of this parameter to a higher value, however, this is fraught negative consequences for the battery itself.

What is required to make a battery?

The main elements of a simple design: a diode and a heater. If you connect them correctly (in series) to the battery, you can achieve what you want - the battery will be charged in 10 hours. But for those who like to save electricity, this solution may not be suitable, because the consumption in this case will be about 10 kW. The operation of the resulting device is not characterized high efficiency.

Basic elements of a simple design

But to create a suitable modification, you will have to slightly modify individual elements, in particular, the transformer, the power of which should be at the level of 200-300 W. Subject to availability old technology, this part from a regular tube TV will do. To organize a ventilation system, a cooler will be useful; it is best if it comes from a computer.

When creating a simple charger for powering a battery with your own hands, the main elements are also a transistor and a resistor. To make the structure work, you will need a compact externally, but quite capacious metal case; a good option is a stabilizer box.

In theory, even a novice radio amateur who has not previously encountered complex circuits can assemble this kind of equipment.

Scheme simple device to charge the battery

The main difficulty lies in the need to modify the transformer. At this level of power, the windings are characterized by low voltage levels (6-7V), the current will be equal to 10A. Typically, a voltage of 12V or 24V is required, depending on the type of battery. To obtain such values at the device output, it is necessary to provide parallel connection windings

Step by step assembly

A homemade charger for powering a car battery begins with preparing the core. Winding the wire onto the windings is done with maximum compaction; it is important that the turns fit tightly to each other and there are no gaps left. We must not forget about the insulation, which is installed at intervals of 100 turns. The wire cross-section of the primary winding is 0.5 mm, the secondary winding is from 1.5 to 3.0 mm. If we consider that at a frequency of 50 Hz, 4-5 turns can provide a voltage of 1V, respectively, to obtain 18V, about 90 turns are required.

Next, a diode of suitable power is selected to withstand the loads applied to it in the future. The best option is a car generator diode. To eliminate the risk of overheating, it is necessary to ensure effective air circulation inside the housing of such a device. If the box is not perforated, you should take care of this before starting assembly. The cooler must be connected to the charger output. Its main task is to cool the diode and winding of the transformer, which is taken into account when choosing an area for installation.

Let's watch the video, detailed instructions on production:

The circuit of a simple charger for powering a car battery also contains a variable resistor. For normal charging operation, it is necessary to obtain a resistance of 150 Ohms and a power of 5 W. The KU202N resistor model meets these requirements more than others. You can choose a different option from this, but its parameters should be similar in value to those indicated. The resistor's job is to regulate the voltage at the device's output. Transistor model KT819 is also the best option from a number of analogues.

Efficiency assessment, cost

As you can see, if you need to assemble a homemade charger for a car battery, its circuit is more than simple to implement. The only difficulty is the arrangement of all the elements and their installation in the housing with subsequent connection. But such work can hardly be called labor-intensive, and the cost of all the parts used is extremely low.

Some of the parts, and perhaps all of them, will probably be found at home by a radio amateur, for example, a cooler from an old computer, a transformer from a tube TV, old building from the stabilizer. As for the degree of efficiency, such devices, assembled with your own hands, do not have very high efficiency, however, as a result, they still cope with their task.

Let's watch the video, useful tips specialist:

Thus, large investments in creating homemade charging not required. On the contrary, all the elements cost extremely little, which makes this solution stand out compared to a device that can be purchased ready-made. The scheme discussed above is no different high efficiency, but its main advantage is a charged car battery, albeit after 10 hours. You can improve this option or consider many others proposed for implementation.

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

Who will benefit from this device?

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

Automatic charger circuit

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

PCB

How to do printed circuit board, it's up to you to decide. It is not complicated and therefore can easily be thrown on breadboard. Well, or you can get confused and make it on textolite with etching.

Settings

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