Sooner or later, the car may stop starting due to a low battery charge. Long periods of operation mean that the generator is no longer able to charge the battery. In this case, it is imperative keep at least the simplest charger close at hand for car battery.
Now a new generation of improved models is replacing conventional transformer charging. Pulsed and automatic chargers are very popular among them. Let's get acquainted with the principle of their work, and those who already want to tinker - go
Pulse charging for batteries
Unlike a transformer, a pulse car battery charger provides a full charge. However, its main advantages are ease of use, significantly lower cost and compact size.
The battery is charged by impulse devices 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, therefore, in the event of a breakdown, it is better for an inexperienced owner to purchase a new one.
Lead acid batteries are very temperature sensitive. 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 good at this and do not damage the battery.
Automatic chargers for car batteries
For inexperienced drivers, an automatic charger is best. for car battery. It has a number of functions and protections that will warn you about incorrect connection of the poles and prevent the supply of electric current.
Some devices are designed to measure the capacity and charge level of the battery, so they are used to charge any type of rechargeable battery.
The electrical circuits of automatic devices contain a special timer, thanks to which several different cycles can be carried out: full charge, quick charge and battery recovery. After the completion of the process the device will inform about this and disconnect the load.
Very often, due to improper use of the battery, sulphitation forms on its plates. The charge-discharge cycle not only relieves the battery of emerging salts, but also prolongs its service life.
Despite the low price of modern chargers, there are times when the proper charging is not at hand. So it is quite possible to make a charger for a car battery with your own hands. Consider a few examples of homemade devices.
Charging for the battery from the computer power supply
Someone may have old computers with a working power supply, from which you can get an excellent charger. It will fit almost any battery.
Diagram of a simple charger from a computer power supply
Almost every power supply unit has a PWM in place of DA1 - a controller based on a TL494 microcircuit or a similar KA7500. Charging the battery requires a current of 10% of the battery's full capacity(usually from 55 to 65A * h), so any PSU with a power over 150 W is capable of generating it. Initially, you need to remove unnecessary wires from sources -5 V, -12 V, +5 V, +12 V.
Next, you need to solder resistor R1, which is replaced by a trimming resistor with the highest value of 27 kOhm. The voltage from the + 12V rail will be transmitted to the upper terminal. Then 16 output is disconnected from the main wire, and 14 and 15 are simply cut at the junction.
Approximately this should be the power supply unit at the initial stage of rework. 
Now a potentiometer-current regulator R10 is installed on the rear wall of the power supply, and 2 cords are passed through: one network, the other for connection to the battery terminals... It is recommended to prepare a block of resistors in advance, with the help of which the connection and adjustment is much more convenient.
For its manufacture, two 5W8R2J current-measuring resistors with a power of 5W 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 case and the main circuit. You should pay attention to this for 2 reasons:
The electrical connections and the board with the resistor box are installed according to the above diagram. 
Conclusions 1, 14, 15, 16 on the microcircuit first, you should irradiate, and then solder the multi-stranded thin wires.
The full charge will be determined by the open circuit voltage in the range from 13.8 to 14.2 V... It must be set with a variable resistor at the middle position of the potentiometer R10. To connect the leads to the battery terminals, crocodile clips are installed at their ends. The insulating tubes on the clamps must be of different colors. Usually red corresponds to "plus" and black to "minus". Do not get confused with connecting wires, otherwise it will damage the device..
Ultimately, a car battery charger from a computer power supply should look something like this. 
If the charger will be used exclusively for charging the battery, then the volt and ammeter can be dispensed with. To set the initial current, it is enough to use the calibrated scale of the R10 potentiometer with a value of 5.5-6.5 A. Almost the entire charging process does not require human intervention.
A charger of this type eliminates the possibility of overheating or overcharging the battery.
The simplest memory using an adapter
An adapted 12-volt adapter acts as a constant current source here.... In this case, the car battery charger circuit is not required.
The main thing to consider is an important feature - the voltage of the power supply 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. Further, wires with opposite charges are removed from each other by 40 cm. Then a crocodile is put on the end of each wire(clamp type), each with a different color to avoid polarity confusion. 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 difficulty lies only in 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.
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Household light bulb and diode charger
To create a simple memory device, you will need a few simple elements:
- household light bulb up to 200 watts. The speed of recharging the battery depends on its power - the higher the faster;
- a semiconductor diode that conducts electricity in one direction only. As such a diode can use laptop charger;
- wires with terminals and plug.
The connection diagram of the elements and the battery charging process are clearly demonstrated in this video.
With the correct setup of the circuit, the light will burn at full heat, and if it does not light at all, then the circuit needs to be finalized. It is possible that the lamp 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).
It takes about 10 hours to charge, after which be sure to disconnect the charger from the mains, otherwise overheating of the battery will lead to its failure.
In an emergency, the battery can be recharged using a sufficiently powerful diode and a heater using the mains current method. The sequence for 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 car battery charger can be considered the simplest, but extremely unreliable.
Conclusion
It takes a lot of technical knowledge to create the simplest charger that won't damage your battery. WITH There is a wide range of chargers on the market now with great functionality and a simple interface for work.
Therefore, whenever possible, it is best to carry a reliable device with the assurance 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.
The article will talk about how to make a homemade scheme with your own hands, you can use absolutely any, but the simplest manufacturing option is to rework a computer power supply unit. If you have such a block, it will be quite easy to find its application. To power the motherboards, a voltage of 5, 3.3, 12 volts is used. As you can imagine, the voltage of 12 volts is of interest to you. The charger will allow you to charge batteries with a capacity ranging from 55 to 65 Ampere-hours. In other words, it will be enough to recharge the batteries of most cars.
General view of the circuit
To make the alteration, you need to use the scheme presented in the article. made with your own hands from the power supply unit of a personal computer, it allows you to control the charging current and voltage at the output. It is necessary to pay attention to the fact that there is a short circuit protection - a 10 Ampere fuse. But it is not necessary to install it, since most power supply units of personal computers have protection that turns off the device in the event of a short circuit. Therefore, charger circuits for batteries from power supply units of computers are able to protect themselves from short-circuit.
ShI controller (designated DA1), as a rule, two types of power supply are used - KA7500 or TL494. Now a little theory. Can the computer's power supply normally recharge the battery? The answer is maybe, since lead batteries of most cars have a capacity of 55-65 Ampere-hour. And for normal charging, it needs a current equal to 10% of the battery capacity - no more than 6.5 Amperes. If the power supply has a power of more than 150 W, then its "+12 V" circuit is capable of delivering such a current.
The initial stage of rework
To replicate a simple homemade battery charger, you need to slightly improve the power supply:
- Get rid of all unnecessary wires. Use a soldering iron to remove them so as not to interfere.
- According to the diagram given in the article, find a constant resistor R1, which must be evaporated and replaced with a trimmer with a resistance of 27 kOhm. Subsequently, a constant voltage "+12 V" must be applied to the upper contact of this resistor. Without this, the device will not be able to work.
- The 16th pin of the microcircuit is disconnected from the minus.
- Next, you need to disconnect the 15th and 14th conclusions.
Quite simple, it turns out a homemade scheme, you can use any, but it is easier to make from a computer power supply unit - it is lighter, easier to operate, more affordable. If we compare with transformer devices, then the mass of the devices differs significantly (as well as the dimensions).
Charger adjustments
The back wall will now be the front, it is desirable to make it from a piece of material (textolite is ideal). On this wall, it is necessary to install a charging current regulator, indicated in the diagram R10. A current sense resistor is best used as strong as possible - get two with 5 watts and 0.2 ohms. But it all depends on the choice of battery charger circuit. Some designs do not need to use high-power resistors.
When connected in parallel, a twofold increase in power is obtained, and the resistance becomes equal to 0.1 Ohm. On the front wall there are also indicators - a voltmeter and an ammeter, which allow you to control the corresponding parameters of the charger. To fine-tune the charger, a trimming resistor is used, with the help of which voltage is applied to the 1st pin of the ShI controller.
Device Requirements
Final assembly
Stranded thin wires must be soldered to pins 1, 14, 15 and 16. Their insulation must be reliable so that heating does not occur under load, otherwise the homemade charger for the car will fail. After assembly, you need to set the trimming resistor to a voltage of about 14 Volts (+/- 0.2 V). It is this voltage that is considered normal for charging batteries. Moreover, this value should be in idle mode (without a connected load).
On the wires that connect to the battery, you must install two crocodile clips. One is red, the other is black. These can be purchased at any hardware store or auto parts store. Here is such a simple homemade charger for a car battery. Connection diagrams: black is attached to minus, and red to plus. The charging process is fully automatic, no human intervention is required. But it is worth considering the main stages of this process.
Battery charging process
At the initial cycle, the voltmeter will show a voltage of approximately 12.4-12.5 V. If the battery has a capacity of 55 A * h, then you need to rotate the regulator until the ammeter shows a value of 5.5 Amperes. This means that the charging current is 5.5 A. As the battery charges, the current decreases and the voltage tends to be at its maximum. As a result, at the very end, the current will be 0, and the voltage will be 14 V.
Regardless of which selection of circuits and designs of chargers was used for the manufacture, the principle of operation is in many ways similar. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not run the risk of overcharging the battery. Therefore, the charger can be connected to the battery for a day, a week, or even a month.
If you do not have measuring devices that you would not mind installing in the device, you can refuse them. But for this it is necessary to make a scale for the potentiometer - to indicate the position for the charging current values equal to 5.5 A and 6.5 A. Of course, the installed ammeter is much more convenient - you can visually observe the process of charging the battery. But a do-it-yourself battery charger, made without the use of devices, can be easily operated.
Almost every modern motorist has encountered battery problems. In order to resume its normal operation, you must have a mobile charger. It allows you to reanimate the device in a matter of seconds.
The main component of any charging is a transformer. Thanks to him, you can make a simple do-it-yourself charger at home.
Here you will find out what parts are needed when assembling the structure. Experienced expert advice will help you avoid common mistakes.
How should the battery be charged?
It is necessary to charge the battery according to certain rules that will help extend the operating life of this device. Violation of one of the points can provoke premature damage to parts.
Charging parameters should be selected according to the characteristics of the car battery. This process allows for the adjustment of a specialized device that is sold in specialized departments. As a rule, it has a rather high cost, which makes it not affordable for every consumer.
That is why most people prefer to make a do-it-yourself charger power supply. Before you start the work process, you need to familiarize yourself with the types of chargers for the car.
Varieties of charging for rechargeable batteries
The process of charging batteries is the restoration of lost power. For this, special terminals are used, which produce constant current and constant voltage.
It is important to observe the polarity during the connection. Improper installation will create a short circuit that could ignite parts inside the vehicle.
For quick reanimation of the battery, it is recommended to use constant voltage. It is able to restore the vehicle's performance in 5 hours.
Simple charger circuit
What can a charger be made of? All parts and consumables can be used from old household appliances.
For this you will need:
A step-down transformer. It is found in old tube TVs. It helps to lower 220 V to the required 15 V. The output of the transformer will be an alternating voltage. In the future, it is recommended to straighten it. This requires a rectifying diode. On the diagrams of how to make a charger with your own hands, a drawing of the connections of all elements is shown.
Diode bridge. Thanks to him, negative resistance is obtained. The current is pulsating, but controlled. In some cases, a diode bridge with a smoothing capacitor is used. It provides constant current.
Consumable items. There are fuses as well as meters. They help control the entire charge delivery process.
Multimeter. It will indicate power fluctuations during the charging of the car battery.
This device will become very hot during operation. A special cooler will help prevent overheating of the unit. It will monitor power surges. It is used instead of a diode bridge. The do-it-yourself photo of the charger shows ready-made equipment for recharging a car battery.
The process can be regulated by changing the resistance. For this, a trimming resistor is used. This method is used in most cases.
You can manually adjust the supply current using two transistors and a trimmer. These parts ensure an even supply of constant voltage and ensure the correct voltage level at the output. There are many ideas and instructions on how to make a charger on the Internet.
Diy charger photo
Every motorist sooner or later has problems with the battery. I did not escape this fate either. After 10 minutes of unsuccessful attempts to start my car, I decided that I needed to buy or make a charger myself. In the evening, after making an audit in the garage and finding a suitable transformer there, I decided to do the charging myself.
In the same place, among the unnecessary junk, I also found a voltage stabilizer from an old TV, which, in my opinion, will perfectly fit as a case.
Having studied the endless expanses of the Internet and really assessing my strength, I chose probably the simplest scheme.
Having printed the circuit, I went to a neighbor who is fond of radio electronics. Within 15 minutes, he typed the necessary details for me, cut off a piece of foil-coated PCB and gave me a marker for drawing the boards. After spending about an hour, I drew an acceptable board (the installation is spacious, the dimensions of the case allow). I will not tell you how to poison the board, there is a lot of information about this. I took my creation to a neighbor, and he etched it for me. In principle, one could buy a circuit board and do everything on it, but as they say to a gift horse….
Having drilled all the necessary holes and displaying the transistor pinout on the monitor screen, I took up the soldering iron and after about an hour I had a finished board.
A diode bridge can be bought on the market, the main thing is that it is designed for a current of at least 10 amperes. I found D 242 diodes, their characteristics are quite suitable, and on a piece of PCB I soldered a diode bridge.
The thyristor must be installed on a radiator, as it heats up noticeably during operation.
Separately, I must say about the ammeter. It had to be bought in a store, and the consultant also picked up a shunt there. I decided to modify the circuit a little and add a switch so that it was possible to measure the voltage on the battery. Here, too, a shunt was needed, but when measuring voltage, it is not connected in parallel, but in series. The calculation formula can be found on the Internet, I will add on my own that the power dissipation of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but I had a shunt with a power of 4 watts. The reason is unknown to me, I do not have enough experience in such matters, but, having decided that basically I needed the readings of an ammeter, and not a voltmeter, I measured it. Moreover, in the voltmeter mode, the shunt noticeably heated up in 30-40 seconds. So, having collected everything I needed and checked everything on the stool, I took up the case. Having completely disassembled the stabilizer, I took out all of its filling.
Having marked the front wall, I drilled holes for a variable resistor and a switch, then with a small diameter drill I drilled holes for an ammeter. I finished the sharp edges with a file.
Having smashed my head a little over the location of the transformer and radiator with a thyristor, I settled on this option.
I bought a couple more crocodile clips and everything is ready. A feature of this circuit is that it only works under load, so after assembling the device and not finding the voltage at the terminals with a voltmeter, do not rush to scold me. Just hang at least a car light bulb on the terminals, and you will be happy.
Take the transformer with a voltage on the secondary winding of 20-24 volts. Zener diode D 814. All other elements are shown in the diagram.
Now there is no point in assembling a charger for car batteries on your own: there is a huge selection of ready-made devices in stores, the prices for them are reasonable. However, let's not forget that it's nice to do something useful with your own hands, especially since a simple charger for a car battery can be easily assembled from improvised parts, and its price will be cheap.
The only thing worth warning about right away: circuits without precise adjustment of the current and voltage at the output, which do not have a cut-off current at the end of the charge, are suitable for charging only lead-acid batteries. For AGM and the use of similar chargers will damage the battery!
How to make the simplest transformer device
The circuit of this charger from a transformer is primitive, but functional and is assembled from available parts - the same way the factory chargers of the simplest type are designed.
At its core, it is a full-wave rectifier, hence the requirements for the transformer: since at the output of such rectifiers, the voltage is equal to the nominal AC voltage multiplied by the root of two, then at 10V on the transformer winding we will get 14.1V at the output of the charger. Any diode bridge is taken with a direct current of more than 5 amperes or assembled from four separate diodes, with the same current requirements, a measuring ammeter is also selected. The main thing is to place it on a radiator, which in the simplest case is an aluminum plate of at least 25 cm2 in area.
The primitiveness of such a device is not only a minus: due to the fact that it has neither regulation nor automatic shutdown, it can be used to "reanimate" sulfated batteries. But do not forget about the lack of protection against polarity reversal in this circuit.
The main problem is where to find a transformer of suitable power (at least 60 W) and with a given voltage. Can be used if a Soviet incandescent transformer comes along. However, its output windings have a voltage of 6.3V, so you have to connect two in series, rewinding one of them so that in total you get 10V at the output. An inexpensive transformer TP207-3 is suitable, in which the secondary windings are connected as follows:
At the same time, we unwind the winding between terminals 7-8.
Simple charger with electronic regulation
However, you can do without rewinding by supplementing the circuit with an electronic voltage stabilizer at the output. In addition, such a scheme will be more convenient in garage applications, since it will allow you to adjust the charge current when the supply voltage drops, it is also used for small car batteries, if necessary.
The role of the regulator here is played by the composite transistor KT837-KT814, the variable resistor regulates the current at the output of the device. When assembling the charging, the 1N754A Zener diode can be replaced with the Soviet D814A.
The variable charger circuit is simple to repeat and easy to surface mount without the need for etching the PCB. However, keep in mind that the field-effect transistors are placed on a radiator, the heating of which will be noticeable. It is more convenient to use an old computer cooler by connecting its fan to the charger outputs. Resistor R1 must have a power of at least 5 W, it is easier to wind it from nichrome or fechral yourself or connect 10 one-watt resistors of 10 ohms in parallel. It is possible not to install it, but we must not forget that it protects the transistors in the event of a short circuit.
When choosing a transformer, be guided by the output voltage of 12.6-16V, take either an incandescent transformer by connecting two windings in series, or select a ready-made model with the required voltage.
Video: The simplest battery charger
Alteration of the charger from the laptop
However, you can do without looking for a transformer if you have an unnecessary laptop charger at hand - with a simple alteration, we will get a compact and lightweight switching power supply that can charge car batteries. Since we need to get a voltage at the output of 14.1-14.3 V, no ready-made power supply will work, however, the conversion is simple.
Let's take a look at a section of a typical scheme, according to which devices of this kind are assembled:
In them, the maintenance of a stabilized voltage is carried out by a circuit from a TL431 microcircuit that controls an optocoupler (not shown in the diagram): as soon as the output voltage exceeds the value set by resistors R13 and R12, the microcircuit lights up the optocoupler LED, informs the PWM controller of the converter to reduce the duty cycle of the supplied to the impulse transformer. Hard? In fact, everything is easy to make with your own hands.
Opening the charger, we find not far from the TL431 output connector and two resistors connected to the Ref. It is more convenient to adjust the upper arm of the divider (in the diagram - resistor R13): by decreasing the resistance, we also reduce the voltage at the output of the charger, increasing it - we raise it. If we have a 12 V charger, we need a resistor with a high resistance, if a 19 V charger, then with a lower one.
Video: Charger for car batteries. Short circuit and reverse polarity protection. With your own hands
We solder the resistor and instead of it we install a trimmer, preset by the multimeter to the same resistance. Then, having connected the load (a light bulb from the headlight) to the output of the charger, we plug it into the network and smoothly rotate the trimmer slider, while simultaneously controlling the voltage. As soon as we get a voltage in the range of 14.1-14.3 V, disconnect the charger from the network, fix the trimming resistor engine with varnish (at least for nails) and assemble the case back. It will take no more time than you spent reading this article.
There are also more complex stabilization schemes, and they can already be found in Chinese blocks. For example, here the TEA1761 microcircuit controls the optocoupler:
However, the principle of adjustment is the same: the resistance of the resistor soldered between the positive output of the power supply and the 6th leg of the microcircuit changes. In the above diagram, two paralleled resistors are used for this (thus, a resistance is obtained that comes out of the standard series). We also need to solder a trimmer instead of them and adjust the output to the desired voltage. Here's an example of one of these boards:
By dialing, you can understand that we are interested in a single resistor R32 (circled in red) on this board - we need to solder it.
On the Internet, there are often similar recommendations on how to make a homemade charger from a computer power supply. But keep in mind that they are all essentially reprints of old articles of the early 2000s, and such recommendations are not applicable to more or less modern power supplies. It is no longer possible to simply raise the 12 V voltage to the required value in them, since other output voltages are also monitored, and they will inevitably "float away" with such a setting, and the power supply protection will work. You can use laptop chargers that give out a single output voltage, they are much more convenient for rework.
