Computer power supply charger by hand. We make our own charger for a car battery from a computer and laptop power supply unit. Video about assembling a charger from a computer power supply for a car battery

Surely every car enthusiast has had to assemble a car charger with his own hands. There are a lot of different approaches, ranging from simple transformer circuits to pulse circuits with automatic adjustment. The charger from the computer power supply just occupies the golden mean. It comes at a cheap price, and its parameters do an excellent job of charging car batteries. Today we will tell you how you can assemble a charger from an ATX computer power supply in half an hour. Go!

First you need a working power supply. You can take a very old one with 200 - 250 W, this power will be enough with a reserve. Considering that charging should occur at a voltage of 13.9 - 14.4 V, the most important modification in the unit will be raising the voltage on the 12 V line to 14.4 V. A similar method was used in the article: Charger from a power supply for LED strips.

Attention! In a working power supply, the elements are under dangerous voltage. Don't grab everything with your hands.

First of all, we unsolder all the wires that came out of the power supply. We leave only the green wire; it must be soldered to the negative contacts. (The areas from which the black wires came out are a minus.) This is done to automatically start the unit when connected to the network. I also immediately recommend soldering the wires with terminals to the negative and + 12 V bus (former yellow wires), for convenience and further setup of the charger.

The following manipulations will be performed with the PWM operating mode - for us it is a TL494 microcircuit (there are also a bunch of power supplies with its absolute analogues). We are looking for the first leg of the microcircuit (the lowest left leg), then we look at the track on the back of the board.

Three resistors are connected to the first pin of the microcircuit; we need the one that connects to the pins of the +12 V block. In the photo, this resistor is marked with red varnish.

This resistor must be unsoldered from the board and its resistance measured. In our case it is 38.5 kOhm.

Instead, you need to solder a variable resistor, which you first set to the same resistance of 38.5 kOhm.

By gradually increasing the resistance of the variable resistor, we achieve an output voltage of 14.4 V.

Attention! For each power supply, the value of this resistor will be different, because The circuits and details in the blocks are different, but the algorithm for changing the voltage is the same for everyone. When the voltage rises above 15 V, PWM generation may be disrupted. After this, the unit will have to be rebooted, after first reducing the resistance of the variable resistor.

In our unit, it was not possible to immediately increase the voltage to 14 V, the resistance of the variable resistor was not enough, so we had to add another constant one in series with it.

When the voltage of 14.4 V is reached, you can safely remove the variable resistor and measure its resistance (it was 120.8 kOhm).

In the resistor measurement field, it is necessary to select a constant resistor with as close a resistance as possible.

We made it up from two 100 kOhm and 22 kOhm.

We are testing the work.

At this stage, you can safely close the lid and use the charger. But if you wish, you can connect a digital voltammeter to this unit, this will give us the opportunity to monitor the charging progress.

You can also screw on the handle for easy carrying and cut a hole in the lid for a digital device.

The final test, we make sure that everything is assembled correctly and works well.

Attention! This charger retains the function of short circuit and overload protection. But it does not protect against overturning! Under no circumstances should you connect the battery to the charger with the wrong polarity; the charger will instantly fail.

When converting a power supply into a charger, it is advisable to have a circuit diagram on hand. To make life easier for our readers, we have made a small selection of ATX computer power supply diagrams.

There are a lot of interesting schemes to protect against polarity reversal. One of them can be found in this article.

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A battery charger from a power supply is a useful and inexpensive device in half an hour

To recharge the battery, the best option is a ready-made charger (charger). But you can do it yourself. There are many different ways to assemble a homemade charger: from the simplest circuits using a transformer, to pulse circuits with adjustable capabilities. The medium in complexity of implementation is the memory from a computer power supply. The article describes how to make a charger from a computer power supply for a car battery with your own hands.

Homemade charger from a power supply

Converting a computer power supply into a charger is not difficult, but you need to know the basic requirements for chargers designed to charge car batteries. For a car battery, the charger must have the following characteristics: the maximum voltage supplied to the battery must be 14.4 V, the maximum current depends on the charger itself. These are the conditions that are created in the electrical system of a car when the battery is recharged from a generator (video author Rinat Pak).

Tools and materials

Taking into account the requirements described above, to make a charger with your own hands, you first need to find a suitable power supply. A used ATX in working condition with a power of 200 to 250 W is suitable.

We take as a basis a computer that has the following characteristics:

• output voltage 12V;
• rated voltage 110/220 V;
• power 230 W;
• the maximum current value is not more than 8 A.

Tools and materials you will need:

• soldering iron and solder;
• screwdriver;
• 2.7 kOhm resistor;
• 200 Ohm and 2 W resistor;
• 68 Ohm resistor and 0.5 W;
• resistor 0.47 Ohm and 1 W;
• resistor 1 kOhm and 0.5 W;
• two 25 V capacitors;
• 12V automotive relay;
• three 1N4007 diodes 1 A;
• silicone sealant;
• green LED;
• voltammeter;
• "crocodiles";
• flexible copper wires 1 meter long.

Having prepared all the necessary tools and spare parts, you can begin to manufacture a charger for the battery from the computer power supply.

Algorithm of actions

The battery should be charged under voltage in the range of 13.9-14.4 V. All computers operate with a voltage of 12V. Therefore, the main task of the modification is to raise the voltage coming from the power supply to 14.4 V. The main modification will be carried out with the PWM operating mode. The TL494 chip is used for this. You can use a power supply with absolute analogues of this circuit. This circuit is used to generate pulses and also as a driver for a power transistor, which performs the function of protecting against high currents. To regulate the voltage at the output of the computer power supply, the TL431 chip, which is installed on an additional board, is used.

Additional board with TL431 chip

There is also a resistor for tuning, which makes it possible to adjust the output voltage in a narrow range.

Work on remaking the power supply consists of the following stages:

1. To make modifications to the block, you first need to remove all unnecessary parts from it and unsolder the wires. What is superfluous in this case is the 220/110 V switch and the wires going to it. The wires should be unsoldered from the power supply. The unit requires a voltage of 220 V to operate. By removing the switch, we will eliminate the possibility of the unit burning out if the switch is accidentally switched to the 110 V position.
2. Next, we unsolder, bite off unnecessary wires, or use any other method to remove them. First, we find the blue 12V wire coming from the capacitor and solder it. There may be two wires, both need to be unsoldered. We only need a bunch of yellow wires with a 12 V output, leaving 4 pieces. We also need ground - these are black wires, we also leave 4 of them. In addition, you need to leave one green wire. The remaining wires are completely removed or soldered.
3. On the board along the yellow wire we find two capacitors in a circuit with a voltage of 12V, they usually have a voltage of 16V, they must be replaced with 25V capacitors. Over time, capacitors become unusable, so even if the old parts are still in working order, it is better to replace them.
4. At the next stage, we need to ensure that the unit operates every time it is connected to the network. The fact is that the power supply in a computer works only if the corresponding wires in the output bundle are short-circuited. In addition, overvoltage protection must be excluded. This protection is installed in order to disconnect the power supply from the electrical network if the output voltage supplied to it exceeds a specified limit. It is necessary to exclude the protection, since the computer is allowed a voltage of 12 V, and we need to get 14.4 V at the output. For the built-in protection, this will be considered overvoltage and it will turn off the unit.
5. The action signal from the overvoltage shutdown protection, as well as the on and off signals, pass through the same optocoupler. There are only three optocouplers on the board. With their help, communication is carried out between the low-voltage (output) and high-voltage (input) parts of the power supply. To prevent the protection from tripping during overvoltage, you need to close the contacts of the corresponding optocoupler with a solder jumper. Thanks to this, the unit will be on all the time if it is connected to the electrical network and will not depend on what voltage is at the output.

   Solder jumper in red circle

6. At the next stage, we need to achieve an outgoing voltage of 14.4 V when operating at idle, because the voltage on the power supply is initially 12 V. For this we need a TL431 chip, which is located on an additional board. Finding her won't be difficult. Thanks to the microcircuit, the voltage is regulated on all tracks that come from the power supply. The tuning resistor located on this board allows you to increase the voltage. But it allows you to increase the voltage value to 13 V, but it is impossible to get a value of 14.4 V.
7. It is necessary to replace the resistor that is connected to the network in series with the trimming resistor. We are replacing it with a similar one, but with lower resistance - 2.7 kOhm. This makes it possible to expand the output voltage setting range and obtain an output voltage of 14.4 V.
8. Next, you need to start removing the transistor, which is located near the TL431 chip. Its presence may affect the correct operation of the TL431, meaning it may prevent the output voltage from being maintained at the required level. In the red circle is the location where the transistor was located.

   Transistor location

9. Then, to obtain a stable output voltage at idle, it is necessary to increase the load on the power supply output through the channel, where the voltage was 12 V, but will become 14.4 V, and through the 5 V channel, but we do not use it. As a load for the first 12 V channel, a resistor with a resistance of 200 Ohms and a power of 2 W will be used, and the 5 V channel will be supplemented for the load with a resistor with a resistance of 68 Ohms and a power of 0.5 W. Once these resistors are installed, the no-load no-load output voltage can be adjusted to 14.4V.
10. Next you need to limit the output current. It is individual for each power supply. In our case, its value should not exceed 8 A. To achieve this, you need to increase the value of the resistor in the primary circuit of the winding of the power transformer, which is used as a sensor used to determine overload. To increase the value, the installed resistor must be replaced with a more powerful one with a resistance of 0.47 Ohms and a power of 1 W. After this replacement, the resistor will function as an overload sensor, so the output current will not exceed 10 A even if the output wires are shorted, simulating a short circuit.

    Resistor to replace

11. At the last stage, you need to add a circuit to protect the power supply from connecting the charger to the battery with the wrong polarity. This is the circuit that will really be created with your own hands and is not included in the computer power supply. To assemble the circuit, you will need a 12 V automotive relay with 4 terminals and 2 diodes rated for 1 A, for example, 1N4007 diodes. In addition, you need to connect a green LED. Thanks to the diode, it will be possible to determine the charging status. If it lights up, it means the battery is connected correctly and is charging. In addition to these parts, you also need to take a resistor with a resistance of 1 kOhm and a power of 0.5 W. The figure shows the protection circuit.

    Power supply protection circuit

12. The operating principle of the circuit is as follows. The battery with the correct polarity is connected to the output of the charger, that is, the power supply. The relay is activated due to the energy remaining in the battery. After the relay operates, the battery begins to charge from the assembled charger through the closed contact of the power supply relay. Charging confirmation will be indicated by a glowing LED.
13. To prevent overvoltage that occurs when the coil is turned off due to the electromotive force of self-induction, a 1N4007 diode is connected to the circuit in parallel with the relay. It is better to glue the relay to the power supply heatsink with silicone sealant. Silicone remains elastic after drying and is resistant to thermal stress, such as compression and expansion, heating and cooling. When the sealant dries, the remaining elements are attached to the relay contacts. Instead of sealant, bolts can be used as fasteners.

    Installation of the remaining elements

14. It is better to choose wires for the charger of different colors, for example, red and black. They should have a cross-section of 2.5 square meters. mm, be flexible, copper. The length must be at least a meter. The ends of the wires must be equipped with crocodiles and special clamps with which the charger is connected to the battery terminals. To secure the wires in the body of the assembled device, you need to drill appropriate holes in the radiator. You need to thread two nylon ties through them, which will hold the wires.

Ready charger

To control the charging current, you can also install an ammeter into the charger body. It must be connected in parallel to the power supply circuit. As a result, we have a charger that we can use to charge the car battery and more.

Conclusion

The advantage of this charger is that the battery will not be recharged when using the device and will not deteriorate, no matter how long it is connected to the charger.

The disadvantage of this charger is the absence of any indicators by which one could judge the state of charge of the battery.

It is difficult to determine whether the battery is charged or not. You can calculate the approximate charging time by using the readings on the ammeter and applying the formula: current in Amperes multiplied by time in hours. It was experimentally found that it takes 24 hours, that is, a day, to fully charge a conventional battery with a capacity of 55 A/h.

This charger retains the function of overload and short circuit. But if it is not protected from reverse polarity, you cannot connect the charger to a battery with the wrong polarity, the device will fail.

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Charger from a computer power supply

Hello everyone, today I will tell you how to make a charger for a car battery with your own hands from a computer power supply. So, we take the power supply and remove the top cover or simply disassemble it. We look for a chip on the board and look carefully at it, or rather at its designation, if you find a TL494 or KA7500 chip (or their analogues) there, then you are very lucky and we can You can easily remake this power supply without any additional hassles. We disassemble the power supply, take out the board and unsolder all the wires from it, we will no longer need them. To charge the battery normally, we should increase the output voltage of the power supply, since 12 volts for charging is not enough, we need about 14.4 volts.

We do this, take a tester and use it to find five volts that are suitable for the 13, 14 and 15 legs of the microcircuit and cut the trace, by doing this we turn off the power supply’s protection against voltage increases. And accordingly, when the block is connected to the network, it will turn on immediately. Next, we find 1 leg on the microcircuit, following this path we find 2 resistors and remove them, in my case these are resistors R2 and R1. In their places we solder variable resistors. One adjustable resistor with a handle is 33 Kom, and the second for a screwdriver is 68 Kom. Thus, we have achieved that we can now regulate the voltage at the output over a wide range.

It should look something like the photo. Next, we take a piece of wire, one and a half meters long and with a cross-section of 2.5 squares, we clean it from the sheath. Then we take two crocodiles and solder our wires to them. It is advisable to install a 10 amp fuse on the positive wire.

Now we find + 12 volts and ground on the board, and solder the wires to them. Next, connect the tester to the power supply. Set the variable resistor knob to the left position, using the second resistor (which is under the screwdriver), rotating it to set the lower voltage value to 14.4 volts. Now, by rotating the variable resistor, we can see how our voltage rises, but now it will not drop below 14.4 volts. This completes the block setup.

We begin assembling the power supply. We screw the board into place. For beauty, I installed LED lighting inside. If you install an LED strip like I did, don’t forget to solder a 22 Ohm resistor in series with it, otherwise it will burn out. Also install a 22 Ohm resistor on the fan in the gap of any wire.

I installed a variable resistor on a PCB plate and brought it out. It is needed to adjust the strength of the output current by increasing the voltage at the output; in short, the larger the battery capacity, the more we turn the knob to the right. When I assembled everything, I secured the wires with hot glue. This is how the charger turned out. Now you will not have problems charging the battery.

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Car charger from computer power supply

The power supply of a personal computer can be converted into a car charger without much difficulty. It provides the same voltage and current as when recharging from the car’s standard electrical outlet. The circuit is devoid of homemade printed circuit boards and is based on the concept of maximum ease of modification.

The basis was taken from a personal computer power supply with the following characteristics:

Rated voltage 220/110 V; - output voltage 12 V; - power 230 W;

The maximum current is no more than 8 A.

So, first you need to remove all unnecessary parts from the power supply. They are a 220 / 110 V switch with wires. This will prevent the device from burning out if the switch is accidentally switched to the 110 V position. Then you need to get rid of all the outgoing wires, with the exception of a bundle of 4 black and 2 yellow wires (they are responsible for powering the device).

Next, you should achieve a result where the power supply will always work when connected to the network, and also eliminate overvoltage protection. The protection turns off the power supply if the outgoing voltage exceeds a certain specified value. This needs to be done because the voltage we need should be 14.4 V, instead of the standard 12.0 V.

The on/off signals and surge protection actions pass through one of three optocouplers. These optocouplers connect the low-voltage and high-voltage sides of the power supply. So, in order to achieve the desired result, we should close the contacts of the desired optocoupler using a solder jumper (see photo).

The next step is to set the output voltage to 14.4 V in idle mode. To do this, we are looking for a board with a TL431 chip. It acts as a voltage regulator on all outgoing tracks of the power supply. This board contains a trimming resistor that allows you to change the outgoing voltage in a small range.

The trim resistor may not have enough capabilities (since it allows you to increase the voltage to approximately 13 V). In this case, you need to replace the resistor connected in series with the trimmer with a resistor with lower resistance, namely 2.7 kOhm.

Then you should add a small load consisting of a resistor with a resistance of 200 Ohms and a power of 2 W to the output on the “12 V” channel and a resistor with a resistance of 68 Ohms, with a power of 0.5 W to the output on the “5 V” channel. In addition, you need to get rid of the transistor located next to the TL431 chip (see photo).

It was found that it prevents the voltage from stabilizing at the level we need. Only now, using the tuning resistor mentioned above, we set the output voltage to 14.4 V.

Next, in order for the output voltage to be more stable at idle, it is necessary to add a small load to the output of the unit along the +12 V channel (which we will have +14.4 V), and on the +5 V channel (which we do not use). A 200 Ohm 2 W resistor is used as a load on the +12 V channel (+14.4), and a 68 Ohm 0.5 W resistor is used on the +5 V channel (not visible in the photo, because it is located behind an additional board):

We also need to limit the current at the output of the device to 8-10 A. This current value is optimal for this power supply. To do this, you need to replace the resistor in the primary circuit of the power transformer winding with a more powerful one, namely 0.47 Ohm 1W.

This resistor acts as an overload sensor and the outgoing current will not exceed 10 A even if the output terminals are short-circuited.

The last step is to install a protection circuit to prevent the charger from being connected to the battery with the wrong polarity. To assemble this circuit, we will need a car relay with four terminals, 2 1N4007 diodes (or similar) as well as a 1 kOhm resistor and a green LED, which will indicate that the battery is connected correctly and is charging. The protection circuit is shown in the figure.

The scheme works on this principle. When the battery is correctly connected to the charger, the relay is activated and closes the contact using the energy remaining in the battery. The battery is charged from the charger, which is indicated by the LED. To prevent overvoltage from the self-induced emf that occurs on the relay coil when it is turned off, a 1N4007 diode is connected in parallel with the relay.

The relay with all elements is mounted to the charger radiator using bolts or silicone sealant.

The wires that are used to connect the charger to the battery must be flexible copper, multi-colored (for example, red and blue) with a cross-section of at least 2.5 mm? and about 1 meter long. It is necessary to solder crocodiles to them for convenient connection to the battery terminals.

I would also advise installing an ammeter into the charger body to monitor the charging current. It must be connected in parallel to the circuit “from the power supply”.

The device is ready.

The advantages of such a charger include the fact that when using it, the battery will not be recharged. The disadvantages are the lack of indication of the battery charge level. But to calculate the approximate battery charging time, you can use the data from the ammeter (current “A” * time “h”). In practice, it was found that within a day a battery with a capacity of 60 Ah can be charged 100%.

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Charger from power supply from computer

It all started with the fact that they gave me an ATX power supply from a computer. So it sat in the stash for a couple of years until the need arose to build a compact battery charger. The unit is made on the TL494 chip, well known for the series of power supplies, which makes it possible to easily convert it into a charger. I will not go into details of the operation of the power supply, the modification algorithm is as follows:

1. Clean the power supply from dust. You can use a vacuum cleaner, you can blow it with a compressor, whatever you have at hand. 2. We check its performance. To do this, in the wide connector that goes to the computer motherboard, you need to find the green wire and jump it to minus (black wire), then turn on the power supply and check the output voltages. If the voltage (+5V, +12V) is normal, proceed to step 3.

3. Disconnect the power supply from the network and remove the printed circuit board. 4. Solder off the excess wires, solder a jumper on the green wire and the negative wire on the board. 5. We find a TL494 chip on it, maybe an analogue of the KA7500.

TL494 We unsolder all the elements from pins of the microcircuit No. 1, 4, 13, 14, 15, 16. A resistor and capacitor should remain on pins 2 and 3, we also solder everything else. Often 15-14 legs of the microcircuit are located together on one track, they need to be cut. You can cut the extra tracks with a knife, this will better eliminate installation errors.

Refinement scheme...

Resistor R12 can be made with a piece of thick copper wire, but it is better to take a set of 10 W resistors connected in parallel or a shunt from a multimeter. If you install an ammeter, you can solder it to the shunt. It should be noted here that the wire from the 16th leg should be on the minus load of the power supply, and not on the total mass of the power supply! The correct operation of the current protection depends on this.

7. After installation, we connect an incandescent light bulb, 40-75 W 220V, in series to the unit via the power supply. This is necessary so as not to burn the output transistors if there is an installation error. And we turn on the block to the network. When you turn it on for the first time, the light should blink and go out, and the fan should work. If everything is fine, go to step 8.

8. Using a variable resistor R10, we set the output voltage to 14.6 V. Next, we connect a 12 V, 55 W car light bulb to the output and set the current so that the unit does not turn off when connecting a load of up to 5 A, and turns off when a load is more than 5 A. Current value may be different, depending on the dimensions of the pulse transformer, output transistors, etc... On average, 5 A will be used for a charger.

9. Solder the terminals and go to test the battery. As the battery charges, the charge current should decrease and the voltage should be more or less stable. The end of the charge will be when the current decreases to zero.

How to remove true key program from computer

When converting computer switching power supplies (hereinafter referred to as UPS) with a TL494 control chip into power supplies for powering transceivers, radio equipment and chargers for car batteries, a number of UPSs accumulated that were faulty and could not be repaired, were unstable, or had a control chip of a different type .

They also got around to the remaining power supplies, and after some experimentation they developed the technology for converting them into chargers (hereinafter referred to as chargers) for car batteries.
Also, after the release, emails began to arrive with various questions, like what and how, where to start.

Where to begin?

Before you begin the rework, you should carefully read the book, it provides a detailed description of the operation of the UPS with the TL494 control chip. It would also be a good idea to visit the sites and, where the issues of redesigning computer UPSs are discussed in detail. For those radio amateurs who could not find the specified book, we will try to explain “on the fingers” how to “tame” a UPS.
And so about everything in order.

And so let’s consider the case when the battery is not yet connected. The AC mains voltage is supplied through the thermistor TR1, mains fuse FU1, and noise suppression filter to the rectifier on the diode assembly VDS1. The rectified voltage is smoothed by a filter on capacitors C6, C7, and the output of the rectifier produces a voltage of + 310 V. This voltage is supplied to a voltage converter using powerful key transistors VT3, VT4 with a pulse power transformer Tr2.

Let’s immediately make a reservation that for our charger there are no resistors R26, R27, intended for slightly opening transistors VT3, VT4. The base-emitter junctions of transistors VT3, VT4 are shunted by circuits R21R22 and R24R25, respectively, as a result of which the transistors are closed, the converter does not work, and there is no output voltage.

When the battery is connected to the output terminals Cl1 and Cl2, the VD12 LED lights up, voltage is supplied through the VD6R16 chain to pin No. 12 to power the MC1 microcircuit and through the VD5R12 chain to the middle winding of the matching transformer Tr1 of the driver on transistors VT1, VT2. Control pulses from pins 8 and 11 of the MC1 chip are sent to the driver VT1, VT2, and through the matching transformer Tr1 to the base circuits of the power key transistors VT3, VT4, opening them one by one.

The alternating voltage from the secondary winding of the power transformer Tr2 of the + 12 V voltage generation channel is supplied to a full-wave rectifier based on an assembly of two VD11 Schottky diodes. The rectified voltage is smoothed out by the LC filter L1C16 and goes to the output terminals Cl1 and Cl2. The output of the rectifier also powers the standard fan M1, intended for cooling UPS parts, connected through a damping resistor R33 to reduce the rotation speed of the blades and fan noise.

The battery is connected through terminal Cl2 to the negative output of the UPS rectifier through resistor R17. When the charging current flows from the rectifier to the battery, a voltage drop is formed across resistor R17, which is supplied to pin No. 16 of one of the comparators of the MC1 chip. When the charging current exceeds the set level (by moving the charge current setting resistor R4), the MC1 microcircuit increases the pause between output pulses, reducing the current to the load and thereby stabilizing the battery charging current.

The output voltage stabilization circuit R14R15 is connected to pin No. 1 of the second comparator of the MC1 microcircuit, and is designed to limit its value (at + 14.2 - + 16 V) in the event of the battery being disconnected. When the output voltage increases above the set level, the MC1 microcircuit will increase the pause between output pulses, thereby stabilizing the output voltage.
Microammeter PA1, using switch SA1, is connected to different points of the UPS rectifier, and is used to measure the charging current and voltage on the battery.

As a PWM control regulator MC1, a microcircuit of the TL494 type or its analogues is used: IR3M02 (SHARP, Japan), µA494 (FAIRCHILD, USA), KA7500 (SAMSUNG, Korea), MV3759 (FUJITSU, Japan, KR1114EU4 (Russia).

Let's start the renovation!

We unsolder all the wires from the output connectors, leave five yellow wires (+12 V voltage generation channel) and five black wires (GND, case, ground), twist four wires of each color together and solder them, these ends will subsequently be soldered to output terminals of the memory.

Remove the 115/230V switch and sockets for connecting cords.
In place of the upper socket, we install a PA1 microammeter for 150 - 200 µA from cassette recorders, for example M68501, M476/1. The original scale has been removed and a homemade scale made using the FrontDesigner_3.0 program has been installed instead; scale files can be downloaded from the magazine’s website. We cover the place of the lower socket with tin measuring 45×25 mm and drill holes for the resistor R4 and the switch for the type of measurement SA1. On the rear panel of the case we install terminals Cl 1 and Cl 2.

Also, you need to pay attention to the size of the power transformer (on the board - the larger one), in our diagram (Fig. 5) this is Tr 2. The maximum power of the power supply depends on it. Its height should be at least 3 cm. There are power supplies with a transformer less than 2 cm high. The power of these is 75 W, even if it is written 200 W.

In the case of remaking an AT type UPS, remove resistors R26, R27 that slightly open the transistors of the key voltage converter VT3, VT4. In case of alteration of an ATX type UPS, we remove the parts of the duty converter from the board.

We solder all the parts except: noise suppression filter circuits, high-voltage rectifier VDS1, C6, C7, R18, R19, inverter on transistors VT3, VT4, their base circuits, diodes VD9, VD10, power transformer circuits Tr2, C8, C11, R28, driver on transistors VT3 or VT4, matching transformer Tr1, parts C12, R29, VD11, L1, output rectifier, according to the diagram (Fig. 5).

We should end up with a board that looks something like this (Fig. 6). Even if a microcircuit like DR-B2002, DR-B2003, DR-B2005, WT7514 or SG6105D is used as a control PWM regulator, it is easier to remove them and make them from scratch on TL494. We manufacture the A1 control unit in the form of a separate board (Fig. 7).

The standard diode assembly in the +12 V rectifier is designed for too low a current (6 - 12 A) - it is not advisable to use it, although it is quite acceptable for a charger. In its place, you can install a diode assembly from a 5-volt rectifier (it is designed for a higher current, but has a reverse voltage of only 40 V). Since in some cases the reverse voltage on the diodes in the +12 V rectifier reaches a value of 60 V! , it is better to install an assembly on Schottky diodes with a current of 2×30 A and a reverse voltage of at least 100 V, for example, 63CPQ100, 60CPQ150.

We replace the rectifier capacitors of the 12-volt circuit with an operating voltage of 25 V (16-volt ones often swelled).

The inductance of inductor L1 should be in the range of 60 - 80 µH, we must unsolder it and measure the inductance, we often came across specimens at 35 - 38 µH, with them the UPS operates unstable, buzzes when the load current increases more than 2 A. If the inductance is too high, more 100 μH, reverse voltage breakdown of the Schottky diode assembly may occur if it was taken from a 5-volt rectifier. To improve cooling of the +12 V rectifier winding and the ring core, remove unused windings for the -5 V, -12 V and +3.3 V rectifiers. You may have to wind several turns of wire to the remaining winding until the required inductance is obtained (Fig. 8).

If the key transistors VT3, VT4 were faulty, and the original ones cannot be purchased, then you can install more common transistors like MJE13009. Transistors VT3, VT4 are screwed to the radiator, usually through an insulating gasket. It is necessary to remove the transistors and, to increase thermal contact, coat the gasket on both sides with thermal conductive paste. Diodes VD1 - VD6 designed for a forward current of at least 0.1 A and a reverse voltage of at least 50 V, for example KD522, KD521, KD510.

We replace all electrolytic capacitors on the +12 V bus with a voltage of 25 V. During installation, it is also necessary to take into account that resistors R17 and R32 heat up during operation of the unit; they must be located closer to the fan and away from the wires.
The VD12 LED can be glued to the PA1 microammeter from above to illuminate its scale.

Setup

When setting up the memory, it is advisable to use an oscilloscope; it will allow you to see the pulses at the control points and will help us significantly save time. We check the installation for errors. We connect the rechargeable battery (hereinafter referred to as the battery) to the output terminals. First of all, we check the presence of generation at pin No. 5 of the MS sawtooth voltage generator (Fig. 9).

We check the presence of the indicated voltages according to the diagram (Fig. 5) at pins No. 2, No. 13 and No. 14 of the MC1 microcircuit. We set the resistor R14 slider to the position of maximum resistance, and check for the presence of pulses at the output of the MC1 microcircuit, at pins No. 8 and No. 11 (Fig. 10).

We also check the signal shape between pins No. 8 and No. 11 of MS1 (Fig. 11), on the oscillogram we see a pause between pulses; the lack of pulse symmetry may indicate a malfunction of the basic driver circuits on transistors VT1, VT2.

We check the shape of the pulses on the collectors of transistors VT1, VT2 (Fig. 12),

And also the shape of the pulses between the collectors of these transistors (Fig. 13).

The lack of pulse symmetry may indicate a malfunction of the transistors themselves VT1, VT2, diodes VD1, VD2, the base-emitter junction of transistors VT3, VT4 or their base circuits. Sometimes a breakdown of the base-emitter junction of transistor VT3 or VT4 leads to the failure of resistors R22, R25, the diode bridge VDS1, and only then to the blowing of fuse FU1.

According to the diagram, the left terminal of resistor R14 is connected to a reference voltage source of 16 V (why 16 V - to compensate for losses in the wires and in the internal resistance of a heavily sulfated battery, although 14.2 V is also possible). By reducing the resistance of resistor R14 until the pulses disappear at pins No. 8 and No. 11 of the MS, more precisely at this moment the pause becomes equal to the half-cycle of pulse repetition.

First start-up, testing

A correctly assembled, error-free device starts up immediately, but for safety reasons, instead of a mains fuse, we turn on a 220 V 100 W incandescent lamp; it will serve as a ballast resistor and in an emergency will save the UPS circuit parts from damage.

We set the resistor R4 to the position of minimum resistance, turn on the charger (charger) to the network, and the incandescent lamp should flash briefly and go out. When the charger operates at a minimum load current, the radiators of transistors VT3, VT4 and the diode assembly VD11 practically do not heat up. As the resistance of resistor R4 increases, the charging current begins to increase; at a certain level, the incandescent lamp will flash. Well, that's all, you can remove the llama and put fuse FU1 in place.

If you still decide to install a diode assembly from a 5-volt rectifier (we repeat that it can withstand current, but the reverse voltage is only 40 V), turn on the UPS to the network for one minute, and use resistor R4 to set the current to load 2 - 3 A, turn off the UPS. The radiator with the diode assembly should be warm, but under no circumstances hot. If it is hot, it means that this diode assembly in this UPS will not work for a long time and will definitely fail.

We check the charger at the maximum current into the load; for this it is convenient to use a device connected in parallel with the battery, which will prevent the battery from being damaged by long-term charges during the setup of the charger. To increase the maximum charging current, you can slightly increase the resistance of resistor R4, but you should not exceed the maximum power for which the UPS is designed.

By selecting the resistances of resistors R34 and R35, we set the measurement limits for the voltmeter and ammeter, respectively.

Photos

Installation of the assembled device is shown in (Fig. 14).

Now you can close the lid. The appearance of the charger is shown in (Fig. 15).

Introduction.

I have accumulated a lot of computer power supplies, repaired as a training for this process, but for modern computers they are already rather weak. What to do with them?

I decided to convert it somewhat into a charger for charging 12V car batteries.

Option 1.

So: let's start.

The first one I came across was the Linkworld LPT2-20. This animal turned out to have PWM on the Linkworld LPG-899 m/s. I looked at the datasheet and the power supply diagram and understood - it’s elementary!

What turned out to be simply amazing is that it is powered by 5VSB, that is, our modifications will not affect its operating mode in any way. Legs 1,2,3 are used to control the output voltages of 3.3V, 5V and 12V respectively within the permissible deviations. The 4th leg is also a protection input and is used to protect against deviations of -5V, -12V. We not only don’t need all these protections, but even get in the way. Therefore they need to be disabled.

The points:

The stage of destruction is over, it’s time to move on to creation.

By and large, we already have the charger ready, but it does not have a charging current limitation (although short-circuit protection works). In order for the charger to not give as much to the battery as it fits, we add a circuit to VT1, R5, C1, R8, R9, R10. How does it work? Very simple. As long as the voltage drop across R8 supplied to the base VT1 through the divider R9, R10 does not exceed the opening threshold of the transistor, it is closed and does not affect the operation of the device. But when it starts to open, a branch from R5 and transistor VT1 is added to the divider at R4, R6, R12, thereby changing its parameters. This leads to a voltage drop at the output of the device and, as a consequence, to a drop in the charging current. At the indicated ratings, the limitation begins to work at approximately 5A, smoothly lowering the output voltage with increasing load current. I strongly recommend not to remove this circuit from the circuit, otherwise, with a severely discharged battery, the current may be so large that the standard protection will work, or the power transistors or Schottks will fly out. And you won’t be able to charge your battery, although savvy car enthusiasts will figure out at the first stage to turn on a car lamp between the charger and the battery to limit the charging current.

VT2, R11, R7 and HL1 are engaged in “intuitive” indication of the charge current. The brighter HL1 lights up, the greater the current. You don't have to collect it if you don't want to. Transistor VT2 must be germanium, because the voltage drop across the B-E junction is significantly less than that of silicon. This means that it will open earlier than VT1.

A circuit of F1 and VD1, VD2 provides simple protection against polarity reversal. I highly recommend making it or assembling another one using a relay or something else. You can find many options online.

And now about why you need to leave the 5V channel. 14.4V is too much for a fan, especially considering that under such a load the power supply does not heat up at all, well, except for the rectifier assembly, it heats up a little. Therefore, we connect it to the former 5V channel (now there is about 6V), and it does its job quietly and quietly. Naturally, there are options for powering the fan: stabilizer, resistor, etc. We will see some of them later.

I freely mounted the entire circuit in a place freed from unnecessary parts, without making any boards, with a minimum of additional connections. It all looked like this after assembly:

In the end, what do we have?

The result is a charger with a limitation of the maximum charging current (achieved by reducing the voltage supplied to the battery when the threshold of 5A is exceeded) and a stabilized maximum voltage at 14.4V, which corresponds to the voltage in the vehicle’s on-board network. Therefore, it can be safely used without turning off battery from on-board electronics. This charger can be safely left unattended overnight and the battery will never overheat. In addition, it is almost silent and very light.

If the maximum current of 5-7A is not enough for you (your battery is often very discharged), you can easily increase it to 7-10A by replacing resistor R8 with a 0.1 Ohm 5W. In the second power supply with a more powerful 12V assembly, this is exactly what I did:

Option 2.

Our next test subject will be the Sparkman SM-250W power supply unit, implemented on the widely known and beloved PWM TL494 (KA7500).

Remaking such a power supply is even simpler than on the LPG-899, since the TL494 PWM does not have any built-in protection for channel voltages, but there is a second error comparator, which is often free (as in this case). The circuit turned out to be almost identical to the PowerMaster circuit. I took this as a basis:

Action plan:

This was perhaps the most economical option. You will have much more soldered parts than the spent J. Especially when you consider that the SBL1040CT assembly was removed from the 5V channel, and diodes were soldered there, which in turn were extracted from the -5V channel. All costs consisted of crocodiles, LED and fuse. Well, you can also add legs for beauty and convenience.

Here is the complete board:

If you are afraid of manipulating the 15th and 16th PWM legs, selecting a shunt with a resistance of 0.005 Ohm, eliminating possible crickets, you can convert the power supply to TL494 in a slightly different way.

Option 3.

So: our next “victim” is the Sparkman SM-300W power supply. The circuit is absolutely similar to option 2, but has on board a more powerful rectifier assembly for the 12V channel and more solid radiators. This means we will take more from him, for example 10A.

This option is clear for those circuits where legs 15 and 16 of the PWM are already involved and you don’t want to figure out why and how this can be changed. And it is quite suitable for other cases.

Let's repeat exactly points 1 and 2 from the second option.

Channel 5B, in this case, I completely dismantled.

In order not to frighten the fan with a voltage of 14.4V, a unit was assembled on VT2, R9, VD3, HL1. It does not allow the fan voltage to exceed 12-13V. The current through VT2 is small, the transistor also heats up, you can do without a radiator.

You are already familiar with the principle of operation of reverse polarity protection and the charging current limiter circuit, but here its connection location here it’s different.

The control signal from VT1 through R4 is connected to the 4th leg of the KA7500B (analogous to TL494). It’s not shown in the diagram, but there should have been a 10 kOhm resistor left from the original circuit from the 4th leg to ground, it no need to touch.

This restriction works like this. At low load currents, transistor VT1 is closed and does not affect the operation of the circuit in any way. There is no voltage on the 4th leg, since it is connected to the ground through a resistor. But when the load current increases, the voltage drop across R6 and R7 also increases, respectively, transistor VT1 begins to open and, together with R4 and the resistor to ground, they form a voltage divider. The voltage on the 4th leg increases, and since the potential on this leg, according to the TL494 description, directly affects the maximum opening time of the power transistors, the current in the load no longer increases. At the indicated ratings, the limiting threshold was 9.5-10A. The main difference from the restriction in option 1, despite the external similarity, is the sharp characteristic of the restriction, i.e. When the triggering threshold is reached, the output voltage drops quickly.

Here is the finished version:

By the way, these chargers can also be used as a power source for car radios, 12V portables and other car devices. The voltage is stabilized, the maximum current is limited, it won’t be so easy to burn anything.

Here is the finished product:

Converting a power supply to a charger using this method is a matter of one evening, but don’t you feel sorry for your favorite time?

Then let me introduce:

Option 4.

The basis is taken from the Linkworld LW2-300W power supply with PWM WT7514L (analogue of the LPG-899 already familiar to us from the first version).

Well: we dismantle the elements we don’t need according to option 1, with the only difference being that we also dismantle channel 5B - we won’t need it.

Here the circuit will be more complex; the option of mounting without making a printed circuit board is not an option in this case. Although we will not completely abandon it. Here is the partially prepared control board and the experiment victim itself, not yet repaired:

But here it is after repairs and dismantling of unnecessary elements, and in the second photo with new elements and in the third its reverse side with already glued gaskets for insulating the board from the case.

What is circled in the diagram in Fig. 6 with a green line is assembled on a separate board, the rest was assembled in a place freed from unnecessary parts.

First, I’ll try to tell you how this charger differs from previous devices, and only then I’ll tell you what details are responsible for what.

• The charger is turned on only when an EMF source (in this case, a battery) is connected to it; the plug must be plugged into the network in advance J.
• If for some reason the output voltage exceeds 17V or is less than 9V, the charger is turned off.
• The maximum charging current is regulated by a variable resistor from 4 to 12A, which corresponds to the recommended battery charging currents from 35A/h to 110A/h.
• The charge voltage is automatically adjusted to 14.6/13.9V or 15.2/13.9V depending on the mode selected by the user.
• The fan supply voltage is adjusted automatically depending on the charging current in the range of 6-12V.
• In the event of a short circuit or polarity reversal, an electronic self-resetting 24A fuse is triggered, the circuit of which, with minor changes, was borrowed from the design of the honorary cat of the 2010 competition winner Simurga. I didn’t measure the speed in microseconds (nothing), but the standard power supply protection doesn’t have time to twitch - it’s much faster, i.e. The power supply continues to work as if nothing had happened, only the red LED for the fuse is flashing. Sparks are practically invisible when the probes are shorted, even when the polarity is reversed. So I highly recommend it, in my opinion, this protection is the best, at least of those that I have seen (although it is a little capricious in terms of false alarms in particular, you may have to sit with the selection of resistor values).

Now who is responsible for what:

• R1, C1, VD1 – reference voltage source for comparators 1, 2 and 3.
• R3, VT1 – power supply autostart circuit when the battery is connected.
• R2, R4, R5, R6, R7 – reference level divider for comparators.
• R10, R9, R15 – the output surge protection divider circuit that I mentioned.
• VT2 and VT4 with surrounding elements - electronic fuse and current sensor.
• Comparator OP4 and VT3 with piping resistors - fan speed controller; information about the current in the load, as you can see, comes from the current sensor R25, R26.
• And finally, the most important thing is that comparators 1 to 3 provide automatic control of the charging process. If the battery is sufficiently discharged and “eats” current well, the charger charges in the mode of limiting the maximum current set by resistor R2 and equal to 0.1 C (comparator OP1 is responsible for this). In this case, as the battery charges, the voltage at the charger output will increase and when the threshold of 14.6 (15.2) is reached, the current will begin to decrease. Comparator OP2 comes into operation. When the charge current drops to 0.02-0.03C (where C is the battery capacity and A/h), the charger will switch to recharging mode with a voltage of 13.9V. Comparator OP3 is used solely for indication and has no effect on the operation of the control circuit. Resistor R2 not only changes the maximum charge current threshold, but also changes all levels of charge mode control. In fact, with its help, the capacity of the charged battery is selected from 35A/h to 110A/h, and current limitation is a “side” effect. The minimum charging time will be in the correct position, for 55A/h approximately in the middle. You may ask: “why?”, because if, for example, when charging a 55A/h battery, you set the regulator to the 110A/h position, this will cause a too early transition to the stage of recharging with a reduced voltage. At a current of 2-3A, instead of 1-1.5A, as intended by the developer, i.e. me. And when set to 35A/h, the initial charge current will be small, only 3.5A instead of the required 5.5-6A. So if you don’t plan to constantly go and look and turn the adjustment knob, then set it as expected, it will not only be more correct, but also faster.
• Switch SA1, when closed, switches the charger to the “Turbo/Winter” mode. The voltage of the second stage of charge increases to 15.2V, the third remains without significant changes. It is recommended for charging at sub-zero battery temperatures, in poor condition, or when there is insufficient time for the standard charging procedure; frequent use in the summer with a working battery is not recommended, because it may negatively affect its service life.
• LEDs help you understand what stage the charging process is at. HL1 – lights up when the maximum permissible charge current is reached. HL2 – main charging mode. HL3 – transition to recharging mode. HL4 - shows that the charge is actually complete and the battery consumes less than 0.01C (on old or not very high-quality batteries it may not reach this point, so you shouldn’t wait very long). In fact, the battery is already well charged after igniting the HL3. HL5 – lights up when the electronic fuse trips. To return the fuse to its original state, it is enough to briefly disconnect the load on the probes.

As for setup. Without connecting the control board or soldering resistor R16 into it, select R17 to achieve a voltage of 14.55-14.65V at the output. Then select R16 so that in recharging mode (without load) the voltage drops to 13.8-13.9V.

Here is a photo of the device assembled without the case and in the case:

That's all. The charging was tested on different batteries; it adequately charges both a car battery and a UPS one (although all my chargers charge any 12V batteries normally, because the voltage is stabilized J). But this is faster and is not afraid of anything, neither short circuit nor polarity reversal. True, unlike the previous ones, it cannot be used as a power supply (it really wants to control the process and does not want to turn on if there is no voltage at the input). But, it can be used as a charger for backup batteries without ever turning it off. Depending on the degree of discharge, it will charge automatically, and due to the low voltage in the recharging mode, it will not cause significant harm to the battery even if it is constantly turned on. During operation, when the battery is almost charged, the charger can switch to pulse charging mode. Those. The charging current ranges from 0 to 2A with an interval of 1 to 6 seconds. At first, I wanted to eliminate this phenomenon, but after reading the literature, I realized that this was even good. The electrolyte mixes better, and sometimes even helps restore lost capacity. So I decided to leave it as it is.

Option 5.

Well, I came across something new. This time LPK2-30 with PWM on SG6105. I have never come across such a “beast” for conversion before. But I remembered numerous questions on the forum and user complaints about problems with altering blocks on this m/s. And I made a decision, even though I don’t need exercise anymore, I need to defeat this m/s out of sporting interest and for the joy of people. And at the same time, try out in practice the idea that arose in my head for an original way to indicate the charge mode.

Here he is, in person:

I started, as usual, by studying the description. I found that it is similar to LPG-899, but there are some differences. The presence of 2 built-in TL431s on board is certainly an interesting thing, but... for us it is insignificant. But the differences in the 12V voltage control circuit, and the appearance of an input for monitoring negative voltages, somewhat complicate our task, but within reasonable limits.

As a result of thoughts and short dancing with a tambourine (where would we be without them), the following project arose:

Here is a photo of this block already converted to one 14.4V channel, without the display and control board yet. On the second is its reverse side:

And these are the insides of the assembled block and its appearance:

Please note that the main board has been rotated 180 degrees from its original location so that the heatsinks do not interfere with the installation of the front panel elements.

Overall this is a slightly simplified version 4. The difference is as follows:

• As a source for generating “fake” voltages at the control inputs, 15V was taken from the power supply of the boost transistors. It, complete with R2-R4, does everything you need. And R26 for the negative voltage control input.
• The reference voltage source for the comparator levels was the standby voltage, which is also the power supply of the SG6105. Because, in this case, we do not need greater accuracy.
• Fan speed adjustment has also been simplified.

But the display has been slightly modernized (for variety and originality). I decided to make it based on the principle of a mobile phone: a jar filled with contents. To do this, I took a two-segment LED indicator with a common anode (you don’t need to trust the diagram - I didn’t find a suitable element in the library, and I was too lazy to draw L), and connected it as shown in the diagram. It turned out a little differently than I intended; instead of the middle “g” stripes going out in the charge current limiting mode, it turned out that they were flickering. Otherwise, everything is fine.

The indication looks like this:

The first photo shows the charging mode with a stable voltage of 14.7V, the second photo shows the unit in current limiting mode. When the current becomes low enough, the upper segments of the indicator will light up, and the voltage at the charger output will drop to 13.9V. This can be seen in the photo above.

Since the voltage at the last stage is only 13.9V, you can safely recharge the battery for as long as you like, this will not harm it, because the car’s generator usually provides a higher voltage.

Naturally, in this option you can also use the control board from option 4. You just need to wire the GS6105 as it is here.

Yes, I almost forgot. It is not at all necessary to install resistor R30 this way. It’s just that I couldn’t find a value in parallel with R5 or R22 to get the required voltage at the output. So I turned out in this... unconventional way. You can simply select the denominations R5 or R22, as I did in other options.

Conclusion.

As you can see, with the right approach, almost any ATX power supply can be converted into what you need. If there are new power supply models and the need for charging, then a continuation will be possible.

I congratulate the cat with all my heart on his anniversary! In his honor, in addition to the article, a new tenant was also acquired - the charming gray pussy of Marquis.

Charger from a computer power supply

If you have an old computer power supply lying around, you can find an easy use for it, especially if you are interested in DIY car battery charger.

The appearance of this device is shown in the picture. The conversion is easy to carry out, and allows you to charge batteries with a capacity of 55...65 Ah

i.e. almost any batteries.

A fragment of a schematic diagram of alterations to a standard power supply is shown in the photo:

As DA1 in almost all power supplies (PSUs) of personal computers (PCs) it is used PHI controller TL494 or its analogue KA7500.

Car batteries (AB) have an electrical capacity of 55...65 Ah. Being lead acid batteries, they require a current of 5.5...6.5 A for their charge - 10% of their capacity, and such a current along the “+12V” circuit can be provided by any power supply with a power of more than 150 W.

You must first remove all unnecessary wires from the “-12 V”, “-5 V”, “+5 V”, “+12 V” circuits.

Resistor R1 with a resistance of 4.7 kOhm, which supplies +5 V to pin 1, must be desoldered. Instead, a trimming resistor with a nominal value of 27 kOhm will be used, the upper terminal of which will be supplied with voltage from the +12 V bus.

Conclusion 16 disconnect from the common wire, and cut the connection of the 14th and 15th pins.

The beginning of converting the power supply into an automatic charger is shown in the photograph:

On the back wall of the power supply unit, which will now become the front, we attach the potentiometer-charging current regulator R10 to a board made of insulating material. We also pass and secure the power cord and the cord for connecting to the battery terminals.

For reliable and convenient connection and adjustment, a block of resistors was made:

Instead of the current-measuring resistor C5-16MV with a power of 5 W and a resistance of 0.1 Ohm recommended in the original source, I installed two imported 5WR2J - 5 W; 0.2 Ohm, connecting them in parallel. As a result, their total power became 10 W, and the resistance became the required 0.1 Ohm.

A tuning resistor R1 is installed on the same board to configure the assembled charger.

To eliminate unwanted connections between the device body and the general charging circuit, it is necessary to remove part of the printed track.

Installation of the resistor block board and electrical connections according to the circuit diagram are shown in the photograph:

The photo does not show the solder joints to pins 1, 16, 14, 15 of the microcircuit. These leads must first be tinned, and then thin multi-core wires with reliable insulation must be soldered.

Before final assembly of the device, it is necessary to use variable resistor R1 with the potentiometer R10 in the middle position to set the open-circuit voltage within 13.8...14.2 V. This voltage will correspond to a full charge of the battery.

The complete set of the automatic charger is shown in the photo:

The terminals for connecting to the battery terminals end with alligator clips with stretched insulating tubes of different colors. The red color corresponds to the positive terminal, and the black color corresponds to the negative terminal.

Warning : Under no circumstances should the wire connections be mixed up! This will damage the device!

The charging process of the 6ST-55 battery is illustrated by the photograph:

The digital voltmeter shows 12.45 V, which corresponds to the initial charging cycle. Initially, the potentiometer is set to “5.5”, which corresponds to an initial charge current of 5.5 A. As charging progresses, the voltage on the battery increases, gradually reaching the maximum set by the variable resistor R1, and the charging current decreases, dropping almost to 0 at the end charging.

When fully charged the device switches to voltage stabilization mode, compensating for the self-discharge current of the battery. In this mode, without fear of overcharging or other undesirable phenomena, the device can remain indefinitely.

When repeating the device I came to the conclusion that the use of a voltmeter and an ammeter is completely unnecessary if the charger is used only for charging car batteries, where a voltage of 14.2 V corresponds to a full charge, and to set the initial charging current, the graduated scale of the R10 potentiometer from 5.5 is quite sufficient up to 6.5 A.

The result is a lightweight, reliable device with an automatic charging cycle that does not require human intervention during operation.

There are quite a few different chargers based on a power supply floating around the Internet. So I decided to tell you about the history of the development of my charging scheme. The scheme was created so that our catmobile would still continue to drive in the cold winter, and anyone could assemble it, more or less a radio cat. The main emphasis in the circuit design of chargers is ease of modification. In our age of “Chinization” of electronics and the electronics industry, it is often easier, cheaper and more accessible to take a ready-made AT/ATX power supply and remake it to suit any of your needs, rather than buy separately a power transformer, bridge diodes, thyristor and other parts. First, I’ll tell you about the simplest (well, it couldn’t be simpler!!!) and reliable charger based on an AT power supply, without a current indicator (although no one bothers to install an ammeter).
Well, we found a suitable AT block assembled on the TL494. We wash it, clean it, dry it and lubricate the fan.

A small digression.

About the quality of components for AT and ATX units. I want to talk about an important element of the circuit - a 310 volt filter capacitor in the primary circuit. Not only such a parameter as ripple of the output voltage with the mains frequency under heavy load depends on it, but also, which is very important, the heating of the output switches themselves. If the capacity is not enough, then they have to work up to 35% of their time at a greater pulse width than with normal capacity, since the average rectified voltage is no longer 310 volts, but 250 - 260 volts due to ripples. The controller has to handle such dips by increasing the width and open time of the transistor. Consequently, they have to operate at a higher current than with sufficient capacity. It follows from this: more current - more heating - less efficiency. (It is already small 60 - 75% depending on the block). Having carried out some measurements of older and very old AT power supplies and newer ATX, it turned out that the Chinese have completely lost their conscience. If capacitors were installed before, as it is written on it, so it was. Now the 50% tolerance is always a minus.

I went through hundreds of blocks: It says 470 MKF, you unsolder it and measure - 300 -330 MKF, even a new capacitor - the same story.
Well, okay, let them write what they want: Well, we need to replace in the AT unit, on the basis of which we will build the charging 200 MKF with these same 330 MKF, or even better, 470 MKF (the real 470). It will be easier for transistors.

It's the same story with chokes.

AT throttle: ATX throttle:

They are not finished, and the ring is smaller... The consequence of reducing the inductance of the group stabilization choke will be an acoustic whistle at low currents (1-2 amperes). The inductance of this inductor is calculated based on the continuity of the current through it at minimum loads. When the unit is turned on, it immediately reaches a power of at least 150W (depending on the computer). Certain currents flow through the inductor, no less than a certain value. The inductor can be designed for this minimum current value, but then, when turned on without a load, the current through the inductor will become intermittent, which will lead to some troubles... The PWM control circuit is designed for the case of continuous current, therefore, with intermittent current, the regulation will be go astray, the inductor will sing, the voltages at the outputs will jump, causing additional recharging currents of the electrolytic capacitors... Of course, in this case, the RC feedback correction circuit will come to our aid, but it is impossible to dull the reaction speed to voltage changes indefinitely, In some the torque of the TL494 during a short circuit simply will not have time to reduce the pulse width and the transistors will fail. This process is quite fast. Therefore, you need to be careful with this. Okay, that was a lyrical digression. Let's continue the "tambourine dance" with the charger.

Circuit with a soft charging current characteristic.

Standard AT block board. Let's look at the diagram to see what needs to be desoldered (and there is a lot, a lot of extra stuff that needs to be desoldered), and what to be soldered in order to get the simplest charging for the battery. The circuit is taken as a standard one, a standard AT unit, and the ratings of the already installed elements may differ significantly from yours. There is NO NEED to change them to those indicated in the diagram! We solder only the overvoltage protections that have become unnecessary, 5 volt channel, -12 volt channel. In general, according to the scheme, we leave the following.

As a result, to get a full, adjustable charging of 10 amperes and 15.8 V with a fan controlled by the load current, you need to add only eight parts!!! Namely: replace two electrolytes, add a shunt of a very approximate resistance of 0.01 ohm -0.08 ohm (for example, three centimeters of a shunt from a Chinese cartoon - it works great). Photo of the original shunt (the author's donor was taken from a Soviet Tseshka):

A 120 ohm resistor, 3.9k, and about 18k, a 10k variable resistor, a 10 nano capacitor and turn the winding on the inductor along the -5 volt channel for the fan. Just don’t forget that the fan should now be connected like this: red to the case, and black to -5:.-12V. We solder the shunt into the gap of the pigtail from the power transformer. When you set the resistor to 3.9k, select its resistance based on the charge current of 10 amperes on a real battery. You won't believe it - that's all! This is simply an unprecedented simplicity of converting practically scrap metal into a completely worthy thing! If the diodes on the +12V channel were originally FR302, then you need to replace them with more powerful ones, for example, remove them from a more modern ATX power supply. Moreover, he is not afraid of a short circuit - he is included in the current limitation. But reversing the polarity of the connection to the battery will lead to a big bang! About "KNOW-HOW", unique protection against overload and short circuit will be written in the article. Colored circles and lines indicate added additional elements.

Setting up: All switching on until complete setting is carried out by connecting it to the network only in series with a 60 watt incandescent light bulb. We check the installation.

Setting up the voltage channel.

We connect the multimeter with crocodiles in voltage measurement mode in the range of up to 200 volts. We plug it into the network. The output voltage should be within 16 volts plus/minus 4 volts. If it’s about 5 volts, it means you forgot to replace the resistor in the voltage control circuit (1 pin of TL494) with 18k. If it is about 23-25V, and the output switches gradually heat up without load, then it means that there is a break in the voltage control circuit (1 pin of TL494) or the resistance of 18k is too high, and the unit has reached the full pulse width and still cannot gain voltage to turn on the reverse communications. We set this resistor to a voltage of approximately 15.8 - 16.2 volts. If you set it to 14.4 V, then after about 1 hour the battery will stop charging at all (tested many times on different batteries).

Setting the current channel.

We temporarily replace the resistor connected in series with the current regulator with a 22k trimmer and set it to the position of minimum resistance. We connect the multimeter with crocodiles in current measurement mode in the range of 10 amperes. We connect the unit to the network through a light bulb. If the light flashes and continues to glow brightly, it means something is wrong, check the installation. If the ammeter shows a current in the range from 1 to 4 amperes, then everything is fine. We set the variable resistor to maximum resistance mode, and use the trimming resistor to adjust the current to 15 -16 amperes. Sometimes the light bulb does not allow you to set it this way, so set it to approximately this current. Now, having connected the discharged battery and the ammeter in series to the output, remove the light bulb and plug it into the network. Using a trimming resistor we adjust the current more precisely, but already 10 amperes. Then we unsolder the trimmer, measure and solder in a constant resistor of the same resistance. The cooling fan should rotate at a speed proportional to the current. If at maximum current or short the speed is too high (voltage above 20 volts), then it is necessary to unwind 10 turns from the winding minus 5 volts of the fan power channel. The voltage on the fan with selected turns should be from 6 volts to 17 volts. That's it, the setup is complete.