The topic of car chargers is of interest to many people. From this article you will learn how to convert a computer power supply into a full-fledged charger for car batteries. It will be a pulse charger for batteries with a capacity of up to 120 Ah, that is, charging will be quite powerful.
There is practically no need to assemble anything - you just need to remake the power supply. Only one component will be added to it.
A computer power supply has several output voltages. The main power buses have voltages of 3.3, 5 and 12 V. Thus, for the device to operate, you will need a 12-volt bus (yellow wire).
To charge car batteries, the output voltage should be around 14.5-15 V, therefore, 12 V from a computer power supply is clearly not enough. Therefore, the first step is to raise the voltage on the 12-volt bus to a level of 14.5-15 V.
Then, you need to assemble an adjustable current stabilizer or limiter so that you can set the required charge current.
The charger, one might say, will be automatic. The battery will be charged to the specified voltage with a stable current. As the charge progresses, the current will drop, and at the very end of the process it will be equal to zero.
When starting to manufacture a device, you need to find a suitable power supply. For these purposes, blocks containing the TL494 PWM controller or its full-fledged analogue K7500 are suitable.
When the required power supply is found, you need to check it. To start the unit, you need to connect the green wire to any of the black wires.
If the unit starts up, you need to check the voltage on all buses. If everything is in order, then you need to remove the board from the tin case.
After removing the board, you need to remove all the wires except two black, two green and go to start the unit. It is recommended to solder the remaining wires with a powerful soldering iron, for example, 100 W.
This step will require your full attention, as this is the most important point in the entire remodel. You need to find the first pin of the microcircuit (in the example there is a 7500 chip), and find the first resistor that is applied from this pin to the 12 V bus.
There are many resistors located on the first pin, but finding the right one will not be difficult if you test everything with a multimeter.
After finding the resistor (in the example it is 27 kOhm), you need to unsolder only one pin. To avoid confusion in the future, the resistor will be called Rx.
Now you need to find a variable resistor, say 10 kOhm. Its power is not important. You need to connect 2 wires about 10 cm long each in this way:
One of the wires must be connected to the soldered terminal of the Rx resistor, and the second must be soldered to the board in the place from which the terminal of the Rx resistor was soldered. Thanks to this adjustable resistor, it will be possible to set the required output voltage.
A charge current stabilizer or limiter is a very important addition that should be included in every charger. This unit is made on the basis of an operational amplifier. Almost any “ops” will do here. The example uses the budget LM358. There are two elements in the body of this microcircuit, but only one of them is needed.
A few words about the operation of the current limiter. In this circuit, an op-amp is used as a comparator that compares the voltage across a low-value resistor to a reference voltage. The latter is set using a zener diode. And the adjustable resistor now changes this voltage.
When the voltage value changes, the op amp will try to smooth out the voltage at the inputs and will do this by decreasing or increasing the output voltage. Thus, the “op-amp” will control the field-effect transistor. The latter regulates the output load.
A field-effect transistor needs a powerful one, since all the charging current will pass through it. The example uses IRFZ44, although any other appropriate parameter can be used.
The transistor must be installed on a heat sink, because at high currents it will heat up quite well. In this example, the transistor is simply attached to the power supply housing.
The printed circuit board was wired hastily, but it turned out pretty good.
Now all that remains is to connect everything according to the picture and begin installation.
The voltage is set to around 14.5 V. The voltage regulator does not need to be brought outside. For control on the front panel there is only a charge current regulator, and a voltmeter is also not needed, since the ammeter will show everything that needs to be seen when charging.
You can take a Soviet analog or digital ammeter.
Also on the front panel was a toggle switch for starting the device and output terminals. The project can now be considered complete.
The result is an easy-to-manufacture and inexpensive charger that you can safely replicate yourself.
Attached files:
Good day, gentlemen, radio amateurs! In this article I want to describe the assembly of a simple charger. Even very simple, because it does not contain anything superfluous. After all, by often complicating a circuit we reduce its reliability. In general, here we will consider a couple of options for such simple car chargers, which can be soldered by anyone who has ever repaired a coffee grinder or changed a switch in the hallway)) From my own experience, I can assume that it will be useful to everyone who has at least some connection to technology or electronics. A long time ago I had the idea of assembling a simple charger for the battery of my motorcycle, since the generator sometimes simply cannot cope with charging the latter, and it is especially difficult for it on a winter morning when you need to start it from the starter. Of course, many will say that with a kick starter it is much easier, but then the battery can be thrown out altogether.Electrical circuit of a homemade charger
What is needed for the battery to charge? A source of stable current that would not exceed a certain safe value. In the simplest case, it will be a regular network transformer. It must produce on the secondary the current required for the standard charging mode (1/10 of the battery capacity). And if at the beginning of the charging cycle the load begins to draw a current of a higher value, the voltage will drop on the output winding of the transformer, which means the current will decrease. There are two options for rectifiers:
The latter circuit will allow you to change the value of the charging current by changing the voltage on the battery. If you do not trust the transformer, then the function of the current stabilizer can be assigned to a regular 12-volt car light bulb.
In general, I decided to make the charging quite powerful for myself, using the TS-160 transformer from a Soviet tube TV as a basis, rewound it to suit my needs, the output was 14 volts at 10 amperes, which allows you to charge batteries of a fairly large capacity, including any automobile ones.
Charger housing
The body was assembled from zinc sheet, as I wanted to make it as simple as possible. 
A hole for the fan was cut out at the back of the case, for greater reliability I decided to add active cooling, and there were a bunch of valves, so don’t let them lie idle.
Then he began to make the filling, screwed on the transformer, and also took the diode bridge with a reserve - KRVS-3510
, fortunately they don’t cost much:
I made a hole in the front panel for a voltmeter, and also screwed in a crocodile socket.
It turned out exactly what I wanted - simple and reliable. This unit is mainly used to charge the battery and power 12-volt LED strips.
Well, as a last resort, for setting up car converters. And to reduce interference, after the bridge I installed a pair of capacitors with a total capacity of about 5 thousand uF.
Externally, of course, it could have been done more accurately, but the main thing for me here is reliability, the next in line is the laboratory power supply, and that’s where I’ll put all my design skills into practice. All the best, I was with you Columnist!.)
Discuss the article DIY CAR CHARGER
Compliance with the operating mode of rechargeable batteries, and in particular the charging mode, guarantees their trouble-free operation throughout their entire service life. Batteries are charged with a current, the value of which can be determined by the formula
where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.
A classic charger for a car battery consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats (see Fig. 1) and transistor current stabilizers are used as current regulators.
In both cases, these elements generate significant thermal power, which reduces the efficiency of the charger and increases the likelihood of its failure.
To regulate the charging current, you can use a store of capacitors connected in series with the primary (mains) winding of the transformer and acting as reactances that dampen excess network voltage. A simplified version of such a device is shown in Fig. 2.
In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is insignificant.
The disadvantage in Fig. 2 is the need to provide a voltage on the secondary winding of the transformer one and a half times greater than the rated load voltage (~ 18÷20V).
The charger circuit, which provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.
It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.
Switches Q1 - Q4 can be used to connect various combinations of capacitors and thereby regulate the charging current.
The variable resistor R4 sets the response threshold of K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.
In Fig. Figure 4 shows another charger in which the charging current is smoothly regulated from zero to the maximum value.
The change in current in the load is achieved by adjusting the opening angle of the thyristor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5. The maximum battery charging current is 10A, set with an ammeter. The device is provided on the mains and load side with fuses F1 and F2.
A version of the charger printed circuit board (see Fig. 4), 60x75 mm in size, is shown in the following figure:
In the diagram in Fig. 4, the secondary winding of the transformer must be designed for a current three times greater than the charging current, and accordingly, the power of the transformer must also be three times greater than the power consumed by the battery.
This circumstance is a significant drawback of chargers with a current regulator thyristor (thyristor).
Note:
The rectifier bridge diodes VD1-VD4 and the thyristor VS1 must be installed on radiators.
It is possible to significantly reduce power losses in the SCR, and therefore increase the efficiency of the charger, by moving the control element from the circuit of the secondary winding of the transformer to the circuit of the primary winding. such a device is shown in Fig. 5.
In the diagram in Fig. 5 control unit is similar to that used in the previous version of the device. SCR VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is approximately 10 times less than the charging current, relatively little thermal power is released on the diodes VD1-VD4 and the thyristor VS1 and they do not require installation on radiators. In addition, the use of an SCR in the primary winding circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the current curve shape coefficient (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing a design (for example, use a variable resistor with a plastic axis).
A version of the printed circuit board of the charger in Figure 5, measuring 60x75 mm, is shown in the figure below:
Note:
The rectifier bridge diodes VD5-VD8 must be installed on radiators.
In the charger in Figure 5 there is a diode bridge VD1-VD4 type KTs402 or KTs405 with the letters A, B, C. Zener diode VD3 type KS518, KS522, KS524, or made up of two identical zener diodes with a total stabilization voltage of 16÷24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is unijunction, type KT117A, B, V, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247, etc.). The diodes are installed on radiators with an area of at least 200 sq.cm, and the radiators will become very hot; a fan can be installed in the charger case for ventilation.
Sooner or later, the car may stop starting due to low battery charge. Long-term operation leads to the fact that the generator is no longer able to charge the battery. In this case, it is necessary keep at least a simple charger on hand for a car battery.
Nowadays, conventional transformer charging is being replaced by a new generation of improved models. Pulse and automatic chargers are very popular among them. Let's get acquainted with the principle of their work, and for those who already want to tinker, go
Pulse chargers for batteries
Unlike a transformer, a pulse charger for a car battery provides a full charge. However, its main advantages are ease of use, significantly lower price and compact size.
Charging the battery with pulsed devices is carried out in two stages: first at constant voltage, and then at constant current(often the charging process is automated). Basically, modern chargers consist of the same type, but very complex circuits, so if they break down, it is better for an inexperienced owner to purchase a new one.
Lead acid batteries are very sensitive to temperature. In hot weather, the battery charge level should not be lower than 50%, and in severe frost conditions, not lower than 75%. Otherwise, the battery may stop working and will need to be recharged. Pulse devices are very suitable for this and do not damage the battery.
Automatic chargers for car batteries
For inexperienced drivers, an automatic charger is best for a car battery. It has a number of functions and protections that will notify you of incorrect pole connection and prohibit the flow of electric current.
Some devices are designed to measure the capacity and charge level of a battery, so they are used to charge any type of battery.
The electrical circuits of automatic devices contain a special timer, thanks to which several different cycles can be carried out: full charging, fast charging and battery recovery. After the process is completed the device will inform you about this and turn off the load.
Very often, due to improper use of the battery, sulfitation forms on its plates. The charge-discharge cycle not only rids the battery of salts that have appeared, but also extends its service life.
Despite the low price of modern chargers, there are times when proper charging is not at hand. That's why It’s quite possible to make a charger for a car battery with your own hands. Let's look at a few examples of homemade devices.
Charging the battery from the computer power supply
Some people may still have old computers with a working power supply that could make an excellent charger. It is suitable for almost any battery.
Circuit diagram of a simple charger from a computer power supply
Almost every power supply has a PWM controller in place of DA1 - a controller based on a TL494 chip or a similar KA7500. To charge the battery, a current of 10% of the full battery capacity is required(usually from 55 to 65Ah), so any power supply with a power of over 150 W is capable of producing it. Initially, you need to unsolder unnecessary wires from sources -5 V, -12 V, +5 V, +12 V.
Next, you need to unsolder resistor R1, which is replaced with a trimming resistor with the highest value of 27 kOhm. The voltage from the +12 V bus will be transmitted to the upper pin. Then pin 16 is disconnected from the main wire, and pins 14 and 15 are simply cut at the connection point.
This is approximately what a power supply unit should look like at the initial stage of rework. 
Now a potentiometer-current regulator R10 is installed on the back wall of the power supply, and 2 cords are passed through: one for network, the other for connecting to the battery terminals. It is recommended to prepare a block of resistors in advance, with the help of which connection and adjustment are much more convenient.
To manufacture it, two current measuring resistors 5W8R2J with a power of 5 W are connected in parallel. Eventually the total power reaches 10 W, and the required resistance is 0.1 Ohm. To set up the charger, a trimming resistor is attached to the same board. Some part of the print track needs to be removed. This will help eliminate the possibility of unwanted connections between the device body and the main circuit. You should pay attention to this for 2 reasons:
Electrical connections and a board with a resistor block are installed according to the above diagram. 
Pins 1, 14, 15, 16 on the chip first you should tin and then solder the stranded thin wires.
Full charge will be determined by open circuit voltage ranging from 13.8 to 14.2 V. It must be set with a variable resistor with the potentiometer R10 in the middle position. To connect the leads to the battery terminals, alligator clips are installed at their ends. The insulating tubes on the clamps must be of different colors. Typically, red corresponds to “plus” and black to “minus”. Do not get confused with connecting wires, otherwise this will lead to damage to the device..
Ultimately, a charger for a car battery from a computer power supply should look something like this. 
If the charger will be used exclusively for charging the battery, then you can dispense with the volt and ammeter. To set the initial current, it is enough to use the graduated scale of potentiometer R10 with a value of 5.5-6.5 A. Almost the entire charging process does not require human intervention.
This type of charger eliminates the possibility of overheating or overcharging the battery.
The simplest memory using an adapter
An adapted 12-volt adapter acts as a DC source here.. In this case, a charger circuit for a car battery is not required.
The main thing to take into account is an important feature - The voltage of the power source must be equal to the voltage of the battery itself, otherwise the battery will not charge.
The end of the adapter wire is cut off and exposed to 5 cm. Next, the wires with opposite charges are separated from each other by 40 cm. Then a crocodile is placed on the end of each wire(type of terminals), each of which should be a different color to avoid confusion with polarity. The clamps are connected in series to the battery (“from plus to plus”, “from minus to minus”) and then the adapter is turned on.
The only difficulty is choosing the right power source. It is also worth paying attention to the fact that the battery may overheat during the process. In this case, you need to interrupt charging for a while.
A xenon lamp is one of the best light sources for cars. Find out what the penalty is for xenon before installing it.
Anyone can install parking sensors. You can verify this on this page. Go ahead and find out how to install parking sensors yourself.
Many drivers have proven that the Strelka police radar does not forgive mistakes. By following this link /tuning/elektronika/radar-detektor-protiv-strelki.html you can find out which radar detectors can protect the driver from a fine.
Charger made from a household light bulb and diode
To create a simple memory you will need a few simple elements:
- household light bulb with a power of up to 200 W. The speed of battery charging depends on its power - the higher the faster;
- A semiconductor diode that conducts electricity in only one direction. As such a diode You can use a laptop charger;
- wires with terminals and plug.
The connection diagram of the elements and the battery charging process are clearly demonstrated in this video.
If the circuit is configured correctly, the light bulb will burn at full intensity, and if it does not light up at all, then the circuit needs to be modified. It is possible that the light will not light up if the battery is fully charged, which is unlikely (the voltage at the terminals is high and the current value is low).
Charging takes approximately 10 hours, after which be sure to unplug the charger, otherwise overheating of the battery will lead to its failure.
In emergency cases, you can recharge the battery using a sufficiently powerful diode and a heater using current from the mains. The sequence of connecting to the network should be as follows: diode, heater, battery. This method consumes a large amount of electricity, and the efficiency is significantly low - 1%. This homemade charger for a car battery can be considered the simplest, but extremely unreliable.
Conclusion
Creating the simplest charger that will not damage your battery will require a lot of technical knowledge. WITH There is now a wide selection of chargers on the market with great functionality and a simple interface to work with.
Therefore, if possible, it is better to have a reliable device with you with a guarantee that the battery will not be compromised and will continue to operate reliably.
Take a look at this video. It shows another way to quickly charge the battery with your own hands.
Every motorist has experienced a moment in life when, after turning the key in the ignition, absolutely nothing happened. The starter would not turn, and as a result, the car would not start. The diagnosis is simple and clear: the battery is completely discharged. But having even the simplest one with an output voltage of 12 V on hand, you can restore the battery within one hour and go about your business. How to make such a device with your own hands is described later in the article.
How to properly charge a battery
Before you make a battery charger with your own hands, you should learn the basic rules regarding how to properly charge it. If you do not follow them, the battery life will sharply decrease and you will have to buy a new one, since it is almost impossible to restore the battery.
To set the correct current, you need to know a simple formula: the charge current is equal to the battery discharge current over a period of time equal to 10 hours. This means that the battery capacity should be divided by 10. For example, for a battery with a capacity of 90 A/h, the charge current must be set to 9 Amperes. If you supply more, the electrolyte will heat up quickly and the lead honeycomb may be damaged. At a lower current, it will take a very long time to fully charge.
Now we need to deal with the tension. For batteries whose potential difference is 12 V, the charging voltage should not exceed 16.2 V. This means that for one bank the voltage should be within 2.7 V.
The most basic rule for proper battery charging: do not mix up the terminals when connecting the battery. Incorrectly connected terminals are called polarity reversal, which will lead to immediate boiling of the electrolyte and final failure of the battery.
Required tools and supplies
You can make a high-quality charger with your own hands only if you have prepared tools and consumables under your hands.
List of tools and consumables:
- Multimeter. It should be in every motorist's tool bag. It will be useful not only when assembling the charger, but also in the future during repairs. A standard multimeter includes functions such as measuring voltage, current, resistance and continuity of conductors.
- Soldering iron. A power of 40 or 60 W is sufficient. You cannot use a soldering iron that is too powerful, as high temperatures will lead to damage to dielectrics, for example, in capacitors.
- Rosin. Necessary for a rapid increase in temperature. If the parts are not heated sufficiently, the soldering quality will be too low.
- Tin. The main fastening material is used to improve the contact of two parts.
- Heat-shrink tubing. A newer version of the old electrical tape, it is easy to use and has better dielectric properties.
Of course, tools such as pliers, a flat-head and shaped screwdriver should always be at hand. Having collected all the above elements, you can begin assembling the battery charger.
Sequence of manufacturing charging based on a switching power supply
Do-it-yourself battery charging should not only be reliable and of high quality, but also have a low cost. Therefore, the scheme below is ideal for achieving such goals.
Ready charging based on a switching power supply
What you will need:
- Electronic type transformer from the Chinese manufacturer Tashibra.
- Dinistor KN102. The foreign dinistor is marked DB3.
- Power keys MJE13007 in the amount of two pieces.
- Four KD213 diodes.
- A resistor with a resistance of at least 10 Ohms and a power of 10 W. If you install a lower power resistor, it will constantly heat up and very soon fail.
- Any feedback transformer that can be found in old radios.
You can place the circuit on any old board or buy a plate of inexpensive dielectric material for this. After assembling the circuit, it will need to be hidden in a metal case, which can be made from simple tin. The circuit must be isolated from the housing.
An example of a charger mounted in the case of an old system unit
The sequence of making a charger with your own hands:
- Remake the power transformer. To do this, you need to unwind its secondary winding, since Tashibra pulse transformers provide only 12 V, which is very little for a car battery. In place of the old winding, 16 turns of a new double wire should be wound, the cross-section of which will not be less than 0.85 mm. The new winding is insulated, and the next one is wound on top of it. Only now you need to make only 3 turns, the wire cross-section is at least 0.7 mm.
- Install short circuit protection. To do this you will need the same 10 ohm resistor. It should be soldered into the gap in the windings of the power transformer and the feedback transformer.
Resistor as short circuit protection
- Using four KD213 diodes, solder the rectifier. The diode bridge is simple, can operate with high frequency current, and is manufactured according to a standard design.
Diode bridge based on KD213A
- Making a PWM controller. Necessary in a charger, as it controls all power switches in the circuit. You can make it yourself using a field-effect transistor (for example, IRFZ44) and reverse conduction transistors. Elements of type KT3102 are ideal for these purposes.
PWM=high quality controller
- Connect the main circuit with the power transformer and the PWM controller. After which the resulting assembly can be secured in a self-made housing.
This charger is quite simple, does not require large expenses for assembly, and is lightweight. But circuits made on the basis of pulse transformers cannot be classified as reliable. Even the simplest standard power transformer will produce more stable performance than pulsed devices.
When working with any charger, remember that polarity reversal must not be allowed. This charging is protected from this, but still, mixed-up terminals shorten the life of the battery, and a variable resistor in the circuit allows you to control the charging current.
Simple DIY charger
To make this charger, you will need elements that can be found in a used old-type TV. Before installing them in a new circuit, the parts must be checked with a multimeter.
The main part of the circuit is the power transformer, which cannot be found everywhere. Its marking: TS-180-2. A transformer of this type has 2 windings, the voltage of which is 6.4 and 4.7 V. To obtain the required potential difference, these windings should be connected in series - the output of the first should be connected to the input of the second by soldering or an ordinary terminal block.
Transformer type TS-180-2
You will also need four D242A type diodes. Since these elements will be assembled in a bridge circuit, excess heat will need to be removed from them during operation. Therefore, it is also necessary to find or purchase 4 cooling radiators for radio components with an area of at least 25 mm2.
All that remains is the base, for which you can take a fiberglass plate and 2 fuses, 0.5 and 10A. Conductors can be used of any cross-section, only the input cable must be at least 2.5 mm2.
Charger assembly sequence:
- The first element in the circuit is to assemble a diode bridge. It is assembled according to the standard scheme. The terminal locations should be lowered down, and all diodes should be placed on cooling radiators.
- From the transformer, from terminals 10 and 10′, draw 2 wires to the input of the diode bridge. Now you need to slightly modify the primary windings of the transformers, and to do this, solder a jumper between pins 1 and 1′.
- Solder the input wires to pins 2 and 2′. The input wire can be made from any cable, for example, from any used household appliance. If only a wire is available, then you need to attach a plug to it.
- A fuse rated at 0.5A should be installed in the gap in the wire leading to the transformer. In the positive gap, which will go directly to the battery terminal, there is a 10A fuse.
- The negative wire coming from the diode bridge is soldered in series to an ordinary lamp rated at 12 V, with a power of no more than 60 W. This will help not only control battery charging, but also limit the charging current.
All elements of this charger can be placed in a tin case, also made by hand. Fix the fiberglass plate with bolts, and mount the transformer directly on the housing, having previously placed the same fiberglass plate between it and the sheet metal.
Ignoring the laws of electrical engineering can lead to the charger constantly failing. Therefore, it is worth planning the charging power in advance, depending on which to assemble the circuit. If you exceed the power of the circuit, then the battery will not be properly charged unless the operating voltage is exceeded.
