DIY car battery charger. How to make a battery charger with your own hands the simplest scheme for an automatic charger for a car battery

15.10.2019

Analysis of more than 11 schemes for making memory devices with your own hands at home, new schemes for 2017 and 2018, how to assemble a circuit diagram in an hour.

TEST:

To understand if you have necessary information about batteries and chargers for them, you should pass a small test:

What are the main reasons for discharge car battery on the road?

A) The motorist got out of the vehicle and forgot to turn off the headlights.

b) The battery has become too hot due to sunlight.

Can the battery fail if the car is not used long time(stands in the garage without starting)?

A) If the battery is idle for a long time, it will fail.

B) No, the battery will not deteriorate, it will only need to be charged and it will function again.

What current source is used to recharge the battery?

A) There is only one option - a network with a voltage of 220 volts.

B) 180 volt network.

Is it necessary to remove the battery when connecting a homemade device?

A) It is advisable to dismantle the battery from the installed place, otherwise there will be a risk of damaging the electronics by high voltage.

B) It is not necessary to remove the battery from the specified location.

If you confuse "minus" and "plus" when connecting the charger, will the battery fail?

A) Yes, if connected incorrectly, the equipment will burn out.

B) The charger simply will not turn on, you will need to move the necessary contacts to the right places.

Answers:

A) Headlights not turned off when stopped and sub-zero temperatures are the most common causes of battery discharge on the road.
A) The battery fails if you do not recharge it for a long time when the car is idle.
A) For recharging, a mains voltage of 220 V is used.
A) It is not advisable to charge the battery homemade device unless removed from the vehicle.
A) Do not confuse the terminals, otherwise the home-made device will burn out.

Battery vehicles require periodic charging. The reasons for the discharge can be different - starting from the headlights that the owner forgot to turn off, and to freezing temperatures in the winter on the street. For recharge battery good Charger. Such a device in large varieties is presented in auto parts stores. But if there is no opportunity or desire to buy, then memory you can do it yourself at home. There are also a large number of schemes - it is advisable to study them all in order to choose the most suitable option.

Definition: The car charger is designed to transmit electric current with a given voltage directly to battery.

Answers to 5 frequently asked questions

Are there any additional measures required before charging? battery on your car?– Yes, you will need to clean the terminals, as acid deposits appear on them during operation. Contacts you need to clean it very well so that the current flows to the battery without difficulty. Sometimes motorists use grease to process the terminals, it should also be removed.
How to wipe the terminals of the chargers?- You can buy a specialized tool in a store or cook it yourself. Water and soda are used as a self-made solution. The components are mixed and mixed. This great option for all surfaces. When the acid comes into contact with soda, a reaction will occur and the motorist will definitely notice it. This place will need to be thoroughly wiped to get rid of all acids. If the terminals were previously treated with grease, then it is removed with any clean rag.
If there are covers on the battery, do they need to be opened before charging?- If there are covers on the case, then they must be removed.
Why is it necessary to unscrew the caps from the battery?- This is necessary so that the gases formed during the charging process freely exit the case.
Is there a need to pay attention to the electrolyte level in the battery?- This is done in without fail. If the level is lower than required, then it is necessary to add distilled water inside the battery. It is not difficult to determine the level - the plates must be completely covered with liquid.

It is also important to know: 3 nuances about operation

Homemade by the method of operation is somewhat different from the factory version. This is due to the fact that the purchased unit has built-in functions, helping at work. They are difficult to install on a device assembled at home, and therefore you will have to follow a few rules when operation.

The DIY charger will not turn off when the battery is fully charged. That is why it is necessary to periodically monitor the equipment and connect to it multimeter- for charge control.
You need to be very careful not to confuse "plus" and "minus", otherwise Charger will burn.
The equipment must be turned off when connecting to charger.

By following these simple rules, it will be possible to properly recharge battery and prevent unpleasant consequences.

Top 3 charger manufacturers

If there is no desire or opportunity to collect memory, then take a look at the following manufacturers:

Stack.
Sonar.
Hyundai.

How to avoid 2 mistakes when charging a battery

Basic rules must be followed in order to feed properly battery by car.

Directly to the mains battery not allowed to connect. For this purpose, chargers are intended.
Even device it is made of high quality and from good materials, you still need to periodically monitor the process charging, so that trouble doesn't happen.

Performance simple rules ensure reliable operation of self-made equipment. It is much easier to monitor the unit than after spending money on components for repairs.

The simplest battery charger

Scheme of 100% working memory for 12 volts

Look at the diagram in the picture memory at 12 V. The equipment is intended for charging car batteries with a voltage of 14.5 volts. The maximum current obtained when charging is 6 A. But the device is also suitable for other batteries - lithium-ion, since the voltage and output current can be adjusted. All the main components for assembling the device can be found on the Aliexpress website.

Required components:

dc-dc buck converter.
Ammeter.
Diode bridge KVRS 5010.
Hubs 2200 uF at 50 volts.
transformer TS 180-2.
Circuit breakers.
Plug for connecting to the network.
"Crocodiles" for connecting terminals.
Radiator for diode bridge.

Transformer any one is used, at its own discretion. The main thing is that its power should be at least 150 W (with charging current in 6 A). It is necessary to install thick and short wires on the equipment. The diode bridge is fixed on a large radiator.

Look at the picture for the charger circuit Dawn 2. It is based on the original memory. If you master this scheme, then you will independently be able to create a high-quality copy that is no different from the original sample. Structurally, the device is a separate unit, closed by a case to protect the electronics from moisture and bad weather conditions. It is necessary to connect a transformer and thyristors on radiators to the base of the case. You will need a board that will stabilize the current charge and control the thyristors and terminals.

1 smart memory circuit

Look at the picture for a schematic diagram of a smart charger. The device is necessary for connection to lead-acid batteries having a capacity of 45 amperes per hour or more. This type of device is connected not only to batteries that are used daily, but also to those on duty or in reserve. This is a fairly budget version of the equipment. It does not provide indicator, and the microcontroller can be bought the cheapest.

If you have the necessary experience, then the transformer is assembled by hand. There is no need to set also the audible alerts - if battery connects incorrectly, the discharge lamp will illuminate to indicate an error. The equipment must be supplied with a switching power supply for 12 volts - 10 amperes.

1 industrial memory circuit

Look at the diagram of the industrial charger from Bars 8A equipment. Transformers are used with one 16 Volt power winding, several vd-7 and vd-8 diodes are added. This is necessary in order to provide a bridge rectifier circuit from one winding.

1 inverter device circuit

Look at the picture for an inverter charger diagram. This device discharges the battery to 10.5 volts before starting charging. The current is used with the value of C/20: "C" indicates the capacity of the installed battery. Thereafter process the voltage rises to 14.5 volts, using a discharge-charge cycle. The charge to discharge ratio is ten to one.

1 wiring diagram memory electronics

1 powerful memory circuit

Look at the picture for a diagram of a powerful charger for a car battery. The device is used for acid battery, having a high capacity. The device easily charges a car battery with a capacity of 120 A. The output voltage of the device is self-adjusting. It ranges from 0 to 24 volts. Scheme It is notable for the fact that few components are installed in it, but it does not require additional settings during operation.

Many could already see the Soviet Charger. It looks like a small metal box, and may seem quite unreliable. But this is not so at all. The main difference between the Soviet model and modern models— reliability. The equipment has a constructive power. In the event that to the old device connect the electronic controller, then charger will be able to revive. But if this is no longer at hand, but there is a desire to assemble it, it is necessary to study the scheme.

To features their equipment includes a powerful transformer and a rectifier, with which it is possible to quickly charge even a heavily discharged battery. Many modern devices will not be able to repeat this effect.

Electron 3M

In an hour: 2 do-it-yourself charging concepts

Simple circuits

1 the simplest scheme for an automatic charger for a car battery

Homemade battery chargers usually have a very simple design, and in addition to that, increased reliability just because of the simplicity of the circuit. Another plus from making charging with your own hands is the relative cheapness of components and, as a result, the low cost of the device.

Why prefabricated construction is better than purchased

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 occurred near the house, where there is desired device, then there will be no problem. Otherwise, when there is no suitable equipment to power the battery, and there are not enough funds either, 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 the main, and sometimes not solvable problem at all, unless the battery is recharged in time. Then homemade chargers for powering car batteries will be 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, the car battery can be powered from the vehicle, or more precisely, from an electric generator. After this node, a relay is usually installed, which is responsible for setting the voltage to no more than 14.1V. In order for the battery to be charged to the limit, a higher value of this parameter is required - 14.4V. Accordingly, batteries are used to implement such a task.

The main components of this device are a transformer and a 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 is discharged to a level where the value of this battery parameter was equal to 12V. If charging is characterized by the same value parameter, then as a result, powering the battery will become a difficult task.

Watch the video, the simplest battery charger:

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

Accordingly, the higher the voltage value (tends to 12V), the lower the current. For normal battery operation, it is desirable 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 one, however, this is fraught with 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, such a solution may not be suitable, because in this case the consumption will be about 10 kW. The operation of the resulting device is characterized by low efficiency.

Basic elements of a simple design

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

When a simple do-it-yourself battery charger is created, a transistor and a resistor also act as the main elements. To get the structure working, you will need a compact on the outside, but quite a roomy metal case, a good option is a box from the stabilizer.

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 power level, the windings are characterized by low voltage indicators (6-7V), the current will be 10A. Usually, a voltage of 12V or 24V is required, depending on the battery type. To obtain such values at the output of the device, it is necessary to ensure the parallel connection of the windings.

Staged assembly

A homemade charger for powering a car battery begins with the preparation of the core. The winding of the wire on the windings is carried out with maximum compaction, it is important that the turns fit snugly against each other, and there are no gaps left. We must not forget about the insulation, which is placed at intervals of 100 turns. The cross section of the wire of the primary winding is 0.5 mm, the secondary one is from 1.5 to 3.0 mm. Considering 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 the generator diode of the car. To eliminate the risk of overheating, it is necessary to ensure effective air circulation inside the case of such a device. If the box is not perforated, care should be taken before assembly. The cooler must be connected to the output of the charger. Its main task is to cool the diode and the transformer winding, which is taken into account when choosing a site for installation.

We watch video detailed instructions for manufacturing:

The circuit of a simple charger for powering a car battery also contains a variable resistor. For the normal functioning of charging, it is necessary to obtain a resistance of 150 ohms and a power of 5 watts. More than others, the KU202N resistor model meets these requirements. You can choose a different option, but its parameters must be similar in value to those specified. The purpose of the resistor is to regulate the voltage at the output of the device. The transistor model KT819 is also the best option from a number of analogues.

Evaluation of efficiency, cost

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

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

We watch video helpful tips specialist:

Thus, large investments in the creation of home-made charging are not required. On the contrary, all elements cost very little, which favorably sets off this decision compared to a device that can be purchased off the shelf. The scheme discussed above is not highly efficient, but its main plus is a charged car battery, albeit after 10 hours. You can improve this option or consider many others that are proposed for implementation.

Battery problems are not uncommon. Recharging is necessary to restore working capacity, but normal charging costs decent money, and you can make it from improvised “trash”. The most important thing is to find a transformer with the right characteristics, and making a charger for a car battery with your own hands is literally a matter of a couple of hours (if you have all the necessary parts).

The process of charging batteries must be carried out according to certain rules. Moreover, the charging process depends on the type of battery. Violation of these rules leads to a decrease in capacity and service life. Therefore, the parameters of the charger for a car battery are selected for each specific case. This opportunity is provided by a complex memory with adjustable parameters or purchased specifically for this battery. There is a more practical option - to make a charger for a car battery with your own hands. To know what parameters should be, a little theory.

Types of battery chargers

Charging the battery is the process of restoring the used capacity. To do this, a voltage is applied to the battery terminals, slightly higher than the operating parameters of the battery. Can be served:

D.C. The charge time is at least 10 hours, during all this time a fixed current is supplied, the voltage changes from 13.8-14.4 V at the beginning of the process to 12.8 V at the very end. In this form, the charge accumulates gradually, lasts longer. The disadvantage of this method is that it is necessary to control the process, turn off the charger in time, since the electrolyte can boil during recharging, which will significantly reduce its working life.
Constant pressure. When charging with a constant voltage, the charger produces a voltage of 14.4 V all the time, and the current changes from large values in the first hours of charging, to very small ones - in the last. Therefore, there will be no AB recharge (unless you leave it for a few days). The positive aspect of this method is that the charge time is reduced (90-95% can be gained in 7-8 hours) and the rechargeable battery can be left unattended. But such an “emergency” charge recovery mode has a bad effect on the service life. With frequent use with constant voltage, the battery discharges faster.

In general, if there is no need to rush, it is better to use DC charging. If you need to restore battery performance in a short time, apply constant voltage. If we talk about which one is better to make a charger for a car battery with your own hands, the answer is unequivocal - supplying direct current. Schemes will be simple, consisting of accessible elements.

How to determine the desired parameters when charging with direct current

It has been experimentally established that charge car lead acid batteries (most of them) required by a current that does not exceed 10% of the battery capacity. If the capacity of the battery being charged is 55 A / h, the maximum charge current will be 5.5 A; with a capacity of 70 A / h - 7 A, etc. In this case, you can set a slightly lower current. The charge will go, but more slowly. It will accumulate even if the charge current is 0.1 A. It just takes a very long time to restore the capacity.

Since in the calculations it is assumed that the charge current is 10%, we get the minimum charge time - 10 hours. But this is at full charge battery and should not be allowed. Therefore, the actual charge time depends on the "depth" of the discharge. You can determine the depth of discharge by measuring the voltage at the battery before charging:

To calculate approximate battery charge time, you need to find out the difference between the maximum battery charge (12.8 V) and its current voltage. Multiplying the number by 10 will give you the time in hours. For example, the voltage on the battery before charging is 11.9 V. We find the difference: 12.8 V - 11.9 V = 0.8 V. Multiplying this figure by 10, we get that the charge time will be about 8 hours. This is provided that we will supply a current that is 10% of the battery capacity.

Charger circuits for auto AB

To charge the batteries, a 220 V household mains is usually used, which is converted to low voltage using a converter.

Simple circuits

The most simple and effective method- use of a step-down transformer. It is he who lowers 220 V to the required 13-15 V. Such transformers can be found in old tube TVs (TC-180-2), computer power supplies, and found on the “collapses” of the flea market.

But at the output of the transformer, an alternating voltage is obtained, which must be rectified. They do this with:

In the above diagrams, there are also fuses (1 A) and measuring instruments. They make it possible to control the charging process. They can be excluded from the circuit, but you will have to periodically use a multimeter to control. With voltage control, this is still tolerable (just attach probes to the terminals), then it is difficult to control the current - in this mode measuring device included in the chain break. That is, every time you have to turn off the power, put the multimeter in current measurement mode, turn on the power. disassemble the measuring circuit in reverse order. Therefore, the use of at least a 10 A ammeter is very desirable.

The disadvantages of these schemes are obvious - there is no way to adjust the charge parameters. That is, when choosing an element base, choose the parameters so that the output current is the same 10% of the capacity of your battery (or a little less). You know the voltage - preferably within 13.2-14.4 V. What to do if the current is more than desired? Add a resistor to the circuit. It is placed on the positive output of the diode bridge in front of the ammeter. You select the resistance “in place”, focusing on the current, the power of the resistor is more, since an extra charge will be dissipated on them (10-20 watts or so).

And one more thing: a do-it-yourself car battery charger made according to these schemes will most likely get very hot. Therefore, it is desirable to add a cooler. It can be inserted into the circuit after the diode bridge.

Schemes with the possibility of adjustment

As already mentioned, the disadvantage of all these schemes is the impossibility of adjusting the current. The only possibility is to change the resistance. By the way, you can put a variable tuning resistor here. This will be the easiest way out. But more reliably implemented manual adjustment current in a circuit with two transistors and a trimmer.

The charge current is changed by a variable resistor. It is already after the composite transistor VT1-VT2, so that a small current flows through it. Therefore, the power can be of the order of 0.5-1 watts. Its value depends on the selected transistors, it is selected empirically(1-4.7 kOhm).

A transformer with a power of 250-500 W, a secondary winding of 15-17 V. The diode bridge is assembled on diodes with a working current of 5A and above.

Transistor VT1 - P210, VT2 is selected from several options: germanium P13 - P17; silicon KT814, KT 816. To remove heat, install on a metal plate or radiator (at least 300 cm2).

Fuses: at the input PR1 - 1 A, at the output PR2 - 5 A. Also in the circuit there are signal lamps - the presence of a voltage of 220 V (HI1) and a charge current (HI2). Here you can put any lamps for 24 V (including LEDs).

Pulse chargers for batteries

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

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

The battery charge of a pulsed device, unlike a transformer, is carried out in two stages. The first is the constant voltage, the second is the current. Usually, modern memory devices are based on the same type, but rather complex circuits. So, if this device fails, then the motorist will most likely have to buy a new one.

As for lead-acid batteries, these batteries are basically temperature sensitive. If it is hot outside, then the charge level should be at least half, and if the temperature is minus, then the battery should be at least 75% charged. Otherwise, the memory will simply cease to function and it will need to be recharged. For such purposes, 12-volt impulse chargers are excellent, since they do not have a negative effect on the battery itself (the author of the video is Artem Petukhov).

Automatic chargers for car batteries

If you are a novice motorist, then it would be better for you to use an automatic battery charger. These memory devices are equipped with rich functionality and protective options, which allows you to warn the driver if the connection is incorrect. In addition, the automatic charger will prevent the supply of voltage if it is connected incorrectly. Sometimes charging can independently calculate the charge level and battery capacity.

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

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

How to make a device yourself

How to make a simple homemade one? Several ways are given below (the author of the video is Crazy Hands).

Battery charger from PC power supply

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

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

From the connectors -5 volts, -12 volts, + 5V and +12 V, you should unsolder the wiring.
After that, the resistor R1 is soldered, a 27 kΩ resistor should be installed instead. Also, output 16 must be disconnected from the main drive.
Further, on the back side of the PSU, you need to mount a current regulator of type R10, and also pass two wires - network and for connecting to the terminals. Before you make a rectifier, it is advisable to prepare a block of resistors. To make it, you just need to connect two resistors in parallel to measure current, the power of which will be 5 watts.
To set the rectifier to 12 volts, you also need to install another resistor on the board - a tuning resistor. To avoid possible links between the electrical circuit and the housing, remove a small portion of the track.
Further, on the diagram, it is necessary to irradiate and solder the wires at terminals 14, 15, 16 and 1. Special clamps must be mounted on the terminals so that the terminal can be hooked. In order not to confuse plus and minus, the wires should be marked; for this, insulating tubes can be used.

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

The simplest memory using an adapter

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

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

In general, the method is simple, but the complexity of the method lies in choosing the right source. If during the charging process you notice that the battery is very hot, then you need to interrupt this process for a few minutes.

Memory from a household light bulb and a diode

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

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

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

Conclusion

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

Video "How to build a memory from a diode and a light bulb?"

How to do this type of exercise correctly - find out from the video below (the author of the video is Dmitry Vorobyev).

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 the site 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. Difficult? 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 increase the voltage of 12 V to the desired value in them, since other output voltages are also controlled, and they will inevitably “float away” with this setting, and the protection of the power supply will work. You can use laptop chargers that produce a single output voltage, they are much more convenient for rework.

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