DIY car battery charger. Practical diagrams of universal battery chargers

I tried to insert into the title of this article all the advantages of this scheme, which we will consider, and of course, I did not quite succeed. So let's now consider all the advantages in order.
The main advantage of the charger is that it is fully automatic. The circuit controls and stabilizes the desired battery charging current, controls the battery voltage and, when it reaches the desired level, it will reduce the current to zero.

What batteries can be recharged?

Almost everything: lithium-ion, nickel-cadmium, lead and others. The scope of application is limited only by the charge current and voltage.
For all household needs, this will be enough. For example, if your built-in charge controller is broken, you can replace it with this circuit. Cordless screwdrivers, vacuum cleaners, flashlights and other devices can be charged with this automatic charger, even car and motorcycle batteries.

Where else can you apply the scheme?

In addition to the charger, you can use this circuit as a charging controller for alternative energy sources, such as a solar battery.
Also, the circuit can be used as a regulated power supply for laboratory purposes with short circuit protection.

Main advantages:

• - Simplicity: the circuit contains only 4 fairly common components.
• - Full autonomy: current and voltage control.
• - Chips LM317 have built-in protection against short circuit and overheating.
• - Small dimensions of the final device.
• - Large operating voltage range 1.2-37 V.

Flaws:

• - Charging current up to 1.5 A. This is most likely not a drawback, but a characteristic, but I will define this parameter here.
• - At a current of more than 0.5 A, it requires installation on a radiator. You should also consider the difference between input and output voltage. The greater this difference, the more the chips will heat up.

Diagram of an automatic charger

The diagram does not show the power supply, but only the control unit. The power source can be a transformer with a rectifier bridge, a power supply from a laptop (19 V), a power supply from a phone (5 V). It all depends on what goals you are pursuing.
The scheme can be divided into two parts, each of them functions separately. The current stabilizer is assembled on the first LM317. The stabilization resistor is calculated simply: “1.25 / 1 \u003d 1.25 Ohm”, where 1.25 is a constant that is always the same for everyone and “1” is the stabilization current you need. We calculate, then select the nearest resistor from the line. The higher the current, the more power the resistor needs to take. For current from 1 A - at least 5 watts.
The second half is a voltage stabilizer. Everything is simple here, with a variable resistor you set the voltage of a charged battery. For example, in car batteries, it is somewhere equal to 14.2-14.4. To configure, we connect a load resistor of 1 kOhm to the input and measure the voltage with a multimeter. We set the desired voltage with a trimmer resistor and that's it. As soon as the battery is charged and the voltage reaches the set value, the microcircuit will reduce the current to zero, and charging will stop.
I have personally used such a device to charge lithium-ion batteries. It's no secret that they need to be charged correctly and if you make a mistake, they can even explode. This charger does all the work.

To control the presence of a charge, you can use the scheme described in this article -.
There is also a circuit for turning this microcircuit into one: both current and voltage stabilization. But in this version, not quite linear work is observed, but in some cases it may come in handy.
Informative video, but not in Russian, but you can understand the calculation formulas.

Greetings to all who looked at the light. The review will focus, as you probably already guessed, on the EV-Peak E3 charger-balancing device, which allows you to charge battery packs (2S-4S) based on lithium (Li-Ion / Li-Pol) in 3A current balancing mode. This device is of great interest, first of all, for people who are fond of RC technology and have a large fleet of various model batteries, as well as for converting power tools to lithium. The charger has some features, so whoever is interested in how the device showed itself in operation, you are welcome under cat.

General view of the charger-balancing device EV-Peak E3:


This charger was bought for a specific purpose - fast charging of a screwdriver battery converted to lithium 4S. At the time of purchase, it cost $14.99, something similar in functionality (charge 4S through a balancing output) is simply not available for this money:


Brief performance characteristics:
- Producer - EV-Peak
- Model - e3
- Case - plastic
- Supply voltage - 100-240V
- Charging power - 30W
- Charging current - 3A (fixed, gradually decreasing)
- Balancing current - 400ma
- Types of supported batteries - lithium (Li-Ion / Li-Pol) 2S-4S
- Dimensions - 116mm*72mm*40mm
- Weight - 170g

Equipment:
- EV-Peak E3 charger
- power cord with euro plug 1m long
- instruction


The EV-Peak E3 charger comes in a compact, dark-coloured, heavy-duty corrugated box with the company logo and model name:


At the end of the box, the main specifications of the device and the type of power plug are indicated:


To connect to the mains, use a power cord with a Euro plug about 1 m long:


The kit includes a short instruction manual in English:


In total, the equipment is good, everything is available for work “out of the box”.

Dimensions:

The EV-Peak E3 charger is very compact. Its dimensions are only 116mm*72mm*40mm. Here is a comparison with its analogue in the face of SkyRC e450:


Well, according to tradition, a comparison with a thousandth banknote and a box of matches:


The weight of the charger is small - about 185g:


Appearance:

The EV-Peak E3 is a charger/balancer capable of charging Lithium (Li-Ion/Li-Pol) battery packs (2S-4S) at 3A. The balancing current is about 400mA. Unlike the SkyRC e450, the EV-Peak E3 charger does not have the ability to charge high-voltage lithium batteries (HV 4.35V), lithium phosphate (Li-Fe), and nickel-based (NiCd / NiMH) batteries with some stretch. In addition, there is no choice of charging current, which is one of the main disadvantages of the device. In other words, the EV-Peak E3 charger is ideal for quickly charging high-capacity battery packs from RC models or power tools.
The EV-Peak E3 charger is housed in a black plastic case with multiple ventilation holes on the sides and includes both a charge management circuit and a power supply:


The main concept of the company is simplicity and reliability. In this regard, the EV-Peak E3 charger is devoid of any control buttons, and only a socket for connecting a power cord and a socket for connecting battery assemblies are available to the user. They are located on different ends of the device:


From the opposite end there are three slots for connecting three types of battery assemblies (bottom left - 2S, bottom right - 3S, top - 4S):


On the underside of the case there is a sticker indicating the main characteristics of the device, as well as four plastic legs:


To indicate the process (level) of charge, there are 4 LED indicators:


After connecting the battery, the charge does not start immediately. In standby mode, two indicators flash alternately, and when the battery assembly is connected, the correct connection is first checked, and only then the charge begins.

Operation and operation indication:

On management, everything is trite and simple:
1) First, connect the charger to the network. In this case, two indicators should blink alternately
2) then we connect the battery balancing connector to the appropriate socket. Bottom left is for 2S, bottom right is for 3S, top is for 4S assemblies (two/three/four cell assemblies)
3) the electronics checks the correct connection and starts charging

The main difference between the EV-Peak E3 charger and the similar SkyRC e450 charger is that there is no need to connect the power connector to the device, since power is supplied immediately to the extreme balancing pins:


I would also like to note that this device is fundamentally different from SkyRC e3 and its numerous copies:


In those devices, three independent linear controllers (TP4056 or analogues) are installed, each charging its jar with a current of 0.8-1A. There is no balancing, as such, and the charge begins immediately after connection. The correspondence of the final voltages on the cells leaves much to be desired, however, as well as the charging current. In turn, the EV-Peak E3 charger is built on a slightly different circuitry and “adjusts” the voltage on all cells to the same value (4.2V for each bank).

Charge indication:
- the first indicator flashes - the battery level is less than 25%
- the first indicator is on and the second indicator is flashing - the battery level is from 25% to 50%
- the first, second and third indicators are on - the battery level is from 50% to 75%
- all three are on and the fourth indicator is flashing - the battery level is from 75% to 99% (balancing)
- all four indicators are on - the battery is fully charged

Device disassembly:

Disassembling the EV-Peak E3 charger is quite simple. To do this, unscrew the four screws on the underside of the case:


There are practically no complaints about the quality of installation - the soldering is even, but in some places the flux is not completely washed off:


Chips on the reverse side of the board are larger:


There are practically no complaints about the circuitry of the input filtering part of the power supply: there is a fuse, an X-type filter capacitor (filtering from the interference of the PSU itself), a 68mkF * 400V conder, a two-winding choke and Y-type capacitors to reduce impulse noise (blue):


Lacks, however, a thermistor to limit the inrush current and a varistor to protect against mains voltage surges. Power mosfets and diodes are pressed against a flat aluminum heatsink (plate) through thermal paste:


Unfortunately, we managed to read only on the left the marking of dual Schottky diodes (MBRF20100CT), designed for 100V/20A.
Board revision V1.4:


To many, the similarity of 8-foot mosfets with "folk" linear charge controllers will seem to many, but this is not so. The board has four AO4407A mosfets (one on the back of the board) rated for 30V/12A and four resistor shunts:


In general, the performance is good, some elements are taken with a margin and additionally fixed with sealant. On the top cover of the case there is a cut-out window covered with a sticker:


I suspect that the company's product range has similar models in a similar case, but with a control button or a charge current selection button.

EV-Peak E3 charger test:

Before we start testing, I'll talk a little about balancing. It is designed to equalize the voltage on cells / banks of a battery assembly connected in series with two or more (2S-4S). As you know, there are no batteries with exactly the same parameters, so one discharges a little faster, the other a little slower than the others. Therefore, when charging, one will charge a little faster, the other a little slower. I would like to note an important feature of this model, namely the presence of a “correct” balancing.
For testing, we will assemble a simple stand from a holder / holder for three batteries, three voltmeters and one ampervoltmeter:


As you can see, the batteries are almost completely drained, except for the middle one (10-15% of the capacity for the extreme ones, about 25% for the middle one). There is quite a lot of imbalance on the face. When you connect the battery assembly to the charger, after checking, the charge starts. As in the case of the SkyRC e450 charger, the EV-Peak E3 charger slightly underestimates the charging current (about 2.75A), although everything is within the normal range (10%):


Previously, I have already compared the readings of instruments and DIY voltmeters / ammeters. As an example, a photo of measuring the passing current with a UNI-T UT204A current clamp from a previous review:


The readings are the same as when measured with a True RMS multimeter UNI-T UT61E.
After 30-40 minutes, the charging current begins to gradually decrease:


I do not think that anyone will be interested in the whole charge process in stages, so I will give only some samples:


The EV-Peak E3 charger charges lithium batteries using the CC / CV algorithm, the balancing method is CV phase, i.e. the balancer is not active until any bank (cell) goes into CV mode. When a voltage of 4.16-4.17V is reached on any bank, the balancer is activated and, roughly speaking, temporarily turns off this bank, redirecting the charge energy to the remaining banks. Since the balancing current is only about 400mA, the voltage equalization process with a strong imbalance is not too fast. With a small voltage spread on the banks, balancing takes about 10 minutes, no more.
As a result, a minute before the end of the charge, we have the following indicators:


After turning off, we have the following picture:


Basically, it's good. I would like to see the exact voltage of 4.2V, but perhaps the whole thing is in a poorly assembled stand, because everything is done on “snot”.
A short video of the end of the charge:

Well, for example, a real example of a 2S battery charge, with a capacity of 1200mah:


The charging current is about 2.8A, flows from plus to minus in series through all banks:


There is no current on the middle balancing wire, which once again confirms the circuitry that is different from budget chargers (those on the TP4056 and analogues):


On the negative wire, the same current:


For more details, see the short video:

Features of this model:

Despite all the advantages, the charger also has some features, which is why the scope of the charger narrows somewhat:
- You can not reduce the charging current. For compact RC models with small batteries (2S 500-750mah), the charge current of 3A is excessively high and may cause fire
- Do not charge single batteries (1S). On the other hand, a current of 3A is somewhat large for most battery models at 2600-3500mah, so it can not be considered a minus.
- the charger does not have a "discharge" or "storage" mode. Model "lipolki" are not recommended to be stored fully charged, so at the end of the season it is better to discharge them to a certain value.
- the charger is very easy to use and is perfect for charging high-capacity batteries from RC models or power tools
- the charger does not have an additional socket for power supply from the car's on-board battery or car cigarette lighter, as more "advanced" counterparts, so you can forget about charging model batteries in the field, or you can purchase a separate car inverter 12V -> 220V

Pros:
+ workmanship
+ high charge current (3A)
+ good balance (400ma)
+ built-in PSU
+ easy to manage and use

Minuses:
- charging current is somewhat underestimated (maximum 2.8A)
- there is no possibility to select the charging current (only 3A with a gradual decrease)

Conclusion: this charger was bought for a specific purpose - fast charging of a screwdriver battery converted to lithium. It performs its functions perfectly, there are no complaints, so I can safely recommend those who are not embarrassed by its features ...

I plan to buy +12 Add to favorites Liked the review +36 +51

Small battery charger

On the power of small equipment from galvanic cells and batteries at today's prices, you can literally go broke. It is more profitable, having spent one time, to switch to the use of batteries. In order for them to serve for a long time, they must be properly operated: do not discharge below the permissible voltage, charge with a stable current, and stop charging in time. But if the user himself has to monitor the fulfillment of the first of these conditions, then it is advisable to entrust the fulfillment of the other two to the charger. It is such a device that is described in the article.

During development, the task was to design a device with the following characteristics:

• wide intervals of change of the charging current and voltage of the automatic termination of charging (APZ). providing charging of both individual batteries used to power small-sized equipment, and batteries made up of them with a minimum number of mechanical switches;
• close to uniform scales of regulators, allowing to set the charging current and APL voltage with acceptable accuracy without any measuring instruments;
• high stability of the charging current when the load resistance changes;
• relative simplicity and good repeatability.

The described device fully meets these requirements. It is designed to charge batteries D-0.03, D-0.06. D-0.125, D-0.26, D-0.55. TsNK-0.45, NKGTS-1.8, their imported counterparts and batteries made up of them. Up to the set threshold for turning on the APL system, the battery is charged with a stabilized current, independent of the type and number of cells, while the voltage on it gradually increases as it charges. After the system is triggered, the previously set constant voltage is stably maintained on the battery, and the charging current decreases. In other words, there is no overcharging and discharging of the battery, and it can remain connected to the device for a long time.

The device can be used as a power supply unit for small equipment with adjustable voltage from 1.5 to 13 V and protection against overload and short circuit in the load.

The main technical characteristics of the device are as follows:

• charging current at the "40 mA" limit - 0...40, at the "200 mA" limit - 40...200 mA;
• instability of the charging current when the load resistance changes from 0 to 40 Ohm - 2.5%;
• APZ actuation voltage regulation limits - 1.45 ... 13 V.

The schematic diagram of the device is shown in fig. one.

A current source on a transistor \L "4 is used as a charging current stabilizer. Depending on the position of the switch SA2, the current in the load In is determined by the relations: IН \u003d (UB - UBE) / R10 and IН \u003d (UB - UBE) / (R9 + R10 ), where UB is the voltage at the base of the transistor VT4 relative to the positive bus, V; UBE is the voltage drop at its emitter junction, V; R9, R10 are the resistances of the corresponding resistors, Ohm.

It follows from these expressions that by changing the voltage at the base of the transistor VT4 with a variable resistor R8. load current can be adjusted over a wide range. The voltage across this resistor is maintained by a constant zener diode VD6, the current through which, in turn, is stabilized by a field-effect transistor VT2. All this ensures the instability of the charging current specified in the technical specifications. The use of a voltage-controlled stable current source made it possible to change the charging current down to very small values, to have a current regulator scale close to uniform (R8) and simply switch the limits of its regulation.

APS system. triggered after reaching the maximum allowable voltage on the battery or battery, includes a comparator on the op-amp DA1, an electronic key on the transistor VT3, a zener diode VD5. current stabilizer on the transistor VT1 and resistors R1 - R4. The HL1 LED serves as an indicator of charging and its completion.

When a discharged battery is connected to the device, the voltage on it and the non-inverting input of the op-amp DA1 is less than the exemplary one on the inverting one, which is set by the variable resistor R3. For this reason, the voltage at the output of the op-amp is close to the voltage of the common wire, the transistor VT3 is open, a stable current flows through the battery, the value of which is determined by the positions of the variable resistor R8 and switch SA2.

As the battery charges, the voltage at the inverting input of the op-amp DA1 increases. The voltage at its output also increases, so the transistor VT2 exits the current stabilization mode, VT3 gradually closes and its collector current decreases. The process continues until then. until the zener diode VD6 ceases to stabilize the voltage across resistors R7, R8. With a decrease in this voltage, the transistor VT4 begins to close and the charging current decreases rapidly. Its final value is determined by the sum of the battery self-discharge current and the current flowing through the resistor R11. In other words, from that moment on, the voltage set by the resistor R3 is maintained on the charged battery, and the current necessary to maintain this voltage flows through the battery.

The HL1 LED indicates the inclusion of the device in the network and two phases of the charging process. In the absence of a battery, a voltage is set on the resistor R11, determined by the position of the variable resistor R3 slider. Very little current is required to maintain this voltage, so HL1 glows very faintly. At the moment the battery is connected, the brightness of its glow increases to the maximum, and after the APL system is activated after charging is completed, it abruptly decreases to the average between those mentioned above. If desired, you can limit yourself to two levels of glow (weak, strong), for which it is enough to choose a resistor R6.

The details of the device are mounted on a printed circuit board, the drawing of which is shown in fig. 2. It is made by cutting through the foil and is designed for the installation of fixed resistors MLT, tuning (wire) PPZ-43. capacitors K52-1B (C1) and KM (C2). The VT4 transistor is mounted on a heat sink with an effective heat dissipation area of ​​100 cm2. Variable resistors R3 and R8 (PPZ-11 of group A) are fixed on the front panel of the device and are provided with scales with corresponding marks.

(click to enlarge)

Switches SA1 and SA2 - any type, it is desirable, however, that the contacts used as SA2 are designed for switching current of at least 200 mA.

The mains transformer T1 must provide an alternating voltage of 20 V at a load current of 250 mA on the secondary winding.

Field-effect transistors KP303V can be replaced with KP303G - KP303I, bipolar KT361V - with transistors of the KT361 series. KT3107, KT502 with any letter index (except A), and KT814B - on KT814V, KT814G, KT816V, KT816G. Zener diode D813 (VD5) must be selected with a stabilization voltage of at least 12.5 V. Instead, it is permissible to use D814D or any two low-power zener diodes connected in series with a total stabilization voltage of 12.5 ... 13.5 V. It is possible to replace PPP-11 ( R3, R8) variable resistors of any type of group A, and PPP-43 (R10) - a tuned resistor of any type with a dissipation power of at least 3 W.

Setting up the device begins with the selection of the brightness of the HL1 LED. To do this, switch the switches SA1 and SA2, respectively, to the positions "13 V" and "40 mA". and the engine of the variable resistor R8 - on average, connect a resistor with a resistance of 50 ... 100 Ohms to the sockets XS1 and XS2 and find this position of the engine of the resistor R3. which changes the brightness of the glow HL1. An increase in the difference in the brightness of the glow is achieved by selecting a resistor R6.

Then, the boundaries of the intervals for regulating the charging current and the APL voltage are set. By connecting a milliammeter with a measurement limit of 200 ... 300 mA to the output of the device. move the slider of the resistor R8 to the lower (according to the scheme) position, and the SA2 switch to the "200 mA" position. By changing the resistance of the trimmer resistor R10, the device arrow is deflected to the mark of 200 mA. Then the slider R8 is moved to the upper position and by selecting the resistor R7 they achieve readings of 36 ... 38 mA. Finally, switch SA2 to the "40 mA" position. return the slider of the variable resistor R8 to the lower position and by selecting R9 set the output current in the range of 43 ... 45 mA.

To adjust the limits of the APL voltage regulation interval, switch SA1 is set to the "13 V" position, and a DC voltmeter with a measurement limit of 15 ... 20 V is connected to the device output. positions of the slider of the resistor R3. After that, by moving SA1 to the "4.5 V" position, in the same positions of the R3 slider, set the instrument arrow to 1.45 and 4.5 V by selecting the resistor R2.

During operation, the APL voltage is set at the rate of 1.4 ... 1.45 V per one rechargeable battery.

If the device is not supposed to be used to power radio equipment, the indication of the end of charging by extinguishing the LED can be replaced by its flashing, for which it is enough to enter the hysteresis into the comparator - add the device with resistors R12, R13 (Fig. 3), and remove the resistor R6.

After such refinement, when the set APL voltage value is reached, the HL1 LED will turn off, and the charging current through the battery will completely stop. As a result, the voltage on it will begin to drop, so the current stabilizer will turn on again and the HL1 LED will light up. In other words, when the set voltage is reached, HL1 will start flashing, which is sometimes more obvious than a certain average brightness of the glow. The nature of the battery charging process in both cases remains unchanged.

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 a 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”, that is, the battery must be charged.

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 the 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.