A simple do-it-yourself battery charger. DIY car charger: simple circuits
This is a very simple attachment circuit for your existing charger. Which will control the battery charge voltage and, when the set level is reached, disconnect it from the charger, thereby preventing the battery from overcharging.
This device has absolutely no scarce parts. The entire circuit is built on just one transistor. It has LED indicators that indicate the status: charging in progress or the battery is charged.
Who will benefit from this device?
This device will definitely come in handy for motorists. For those who do not have an automatic charger. This device will turn your regular charger into a fully automatic charger. You no longer have to constantly monitor the charging of your battery. All you need to do is put the battery on charge, and it will turn off automatically only after it is fully charged.Automatic charger circuit
Here is the actual circuit diagram of the machine. In fact, it is a threshold relay that is activated when a certain voltage is exceeded. The response threshold is set by variable resistor R2. For fully charged car battery it is usually equal to - 14.4 V.
You can download the diagram here -
Printed circuit board
How to make a printed circuit board is up to you. It is not complicated and therefore can easily be laid out on a breadboard. Well, or you can get confused and make it on textolite with etching.
Settings
If all the parts are in good working order, setting up the machine is reduced only to setting the threshold voltage with resistor R2. To do this, we connect the circuit to the charger, but do not connect the battery yet. We move resistor R2 to the lowest position according to the diagram. We set the output voltage on the charger to 14.4 V. Then slowly rotate the variable resistor until the relay operates. Everything is set.Let's play with the voltage to make sure that the console works reliably at 14.4 V. After this, your automatic charger is ready for use.
In this video you can watch in detail the process of all assembly, adjustment and testing in operation.
The article will tell you how to make your own homemade Schemes you can use absolutely any, but most simple option manufacturing is the reworking of a computer power supply. If you have such a block, it will be quite easy to find a use for it. To power motherboards, voltages of 5, 3.3, 12 Volts are used. As you understand, the voltage of interest to you is 12 Volts. Charger will allow charging batteries whose capacity ranges from 55 to 65 Ampere-hours. In other words, it is enough to recharge the batteries of most cars.
General view of the diagram
To make the alteration, you need to use the diagram presented in the article. made with your own hands from the power supply of a personal computer, allows you to control the charging current and voltage at the output. It is necessary to pay attention to the fact that there is protection against short circuit - a 10 Ampere fuse. But it is not necessary to install it, since most power supplies of personal computers have protection that turns off the device in the event of a short circuit. Therefore, charger circuits for batteries from computer power supplies are able to protect themselves from short circuits.
The PSI controller (designated DA1), as a rule, is used in the power supply of two types - KA7500 or TL494. Now a little theory. Can the computer's power supply charge the battery properly? The answer is maybe, because lead batteries Most cars have a capacity of 55-65 Amp-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 over 150 W, then its “+12 V” circuit is capable of delivering such current.
Initial stage of remodeling
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.
- Using the diagram given in the article, find a constant resistor R1, which must be unsoldered and in its place install a trimmer with a resistance of 27 kOhm. The upper contact of this resistor must subsequently be applied constant pressure"+12 V". Without this, the device will not be able to operate.
- The 16th pin of the microcircuit is disconnected from the minus.
- Next, you need to disconnect the 15th and 14th pins.
It turns out to be quite simple and homemade. You can use any circuits, but it’s easier to make it from a computer power supply - it’s lighter, easier to use, and more affordable. When compared with transformer devices, the mass of the devices differs significantly (as do the dimensions).
Charger adjustments
The back wall will now be the front; it is advisable to make it from a piece of material (textolite is ideal). A regulator must be installed on this wall charging current, designated R10 in the diagram. It is best to use a current-sensing resistor as powerful as possible - take two with a power of 5 W and a resistance of 0.2 Ohm. But it all depends on the choice of battery charger circuit. Some designs do not require the use of high-power resistors.
When connecting them in parallel, the power is doubled, 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 monitor the relevant parameters of the charger. To fine-tune the charger, a trimming resistor is used, with which voltage is supplied to the 1st pin of the PHI controller.
Device requirements
Final assembly
Multi-core 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 car charger will fail. After assembly, you need to set the voltage with a trimming resistor to about 14 Volts (+/-0.2 V). This is the voltage that is considered normal for charging. batteries. Moreover, this value must be in the mode idle move(without connected load).
You must install two alligator clips on the wires that connect to the battery. One is red, the other is black. These can be purchased at any hardware or auto parts store. This is how you get a simple homemade charger for a car battery. Connection diagrams: black is attached to the minus, and red to the plus. The charging process is completely automatic, no human intervention is required. But it is worth considering the main stages of this process.
Battery charging process
During the initial cycle, the voltmeter will show a voltage of approximately 12.4-12.5 V. If the battery has a capacity of 55 Ah, 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 a maximum. As a result, at the very end the current will be 0 and the voltage will be 14 V.
Regardless of the selection of circuits and designs of chargers used for manufacturing, the operating principle is largely similar. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not risk the battery overcharging. Therefore, the charger can be connected to the battery for a day, a week, or even a month.
If you don't have measuring instruments, which it would not be a shame to install 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 of 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 battery charger, made with your own hands without the use of equipment, can be easily used.
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.
Acid - lead acid batteries 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.
Electrical circuits automatic devices contain a special timer, thanks to which you can carry out several different cycles: full charge, 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 low price 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 the power supply should be like initial stage alterations. 
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
As a source direct current here comes the adapted 12-volt adapter. In this case, a charger circuit for a car battery is not required.
The main thing to consider 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.
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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.
At correct setting circuit, the light bulb will burn at full intensity, and if it does not light up at all, then the circuit needs to be modified. The light may not light if full charge battery, which is unlikely (the voltage at the terminals is high and the current value is small).
Charging takes approximately 10 hours, after which be sure to unplug the charger, otherwise overheating of the battery will lead to its failure.
IN in case of emergency you can recharge the battery using enough powerful diode and a heater using the mains current method. 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.
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.
Option printed circuit board charger (see Fig. 4), size 60x75 mm 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. Diode bridge IR 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.
Now there is no point in assembling a charger for car batteries yourself: in stores huge selection ready-made devices, their prices are reasonable. However, let’s not forget that it’s nice to do something useful with your own hands, especially since a simple charger for a car battery can be assembled from scrap parts, and its price will be a pittance.
The only thing you should immediately warn about is that circuits without precise regulation of the current and voltage at the output, which do not have a current cutoff at the end of charging, are suitable for charging only lead-acid batteries. For AGM and the use of such charges leads to damage to the battery!
How to make a simple transformer device
The circuit of this transformer charger is primitive, but functional and assembled from available parts - the simplest type of factory chargers are designed in the same way.
At its core, it is a full-wave rectifier, hence the requirements for the transformer: since the voltage at the output of such rectifiers is equal to the rated voltage alternating current, multiplied by the root of two, then at 10V on the transformer winding we get 14.1V at the output of the charger. You can take any diode bridge with a direct current of more than 5 amperes or assemble it from four separate diodes; a measuring ammeter is also selected with the same current requirements. The main thing is to place it on a radiator, which in the simplest case is an aluminum plate with an area of at least 25 cm2.
The primitiveness of such a device is not only a disadvantage: due to the fact that it has neither adjustment nor automatic shutdown, it can be used to “reanimate” sulfated batteries. But we must not forget about the lack of protection against polarity reversal in this circuit.
The main problem is where to find a transformer of suitable power (at least 60 W) and with a given voltage. Can be used if a Soviet filament transformer turns up. However, its output windings have a voltage of 6.3V, so you will have to connect two in series, winding one of them so that you get a total of 10V at the output. An inexpensive transformer TP207-3 is suitable, in which the secondary windings are connected as follows:
At the same time, we unwind the winding between terminals 7-8.
Simple electronically regulated charger
However, you can do without rewinding by adding an electronic output voltage stabilizer to the circuit. In addition, such a circuit will be more convenient for garage use, since it will allow you to adjust the charge current during power supply voltage drops; it is also used for small-capacity 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 charger, the 1N754A zener diode can be replaced with the Soviet D814A.
The variable charger circuit is easy to replicate and can be easily assembled without the need to etch the printed circuit board. However, please note that field effect transistors 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 outputs of the charger. 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 10 ohm resistors in parallel. You don’t have to install it, but we must not forget that it protects the transistors in the event of a short circuit.
When choosing a transformer, focus on an output voltage of 12.6-16V; take either a filament transformer by connecting two windings in series, or select a ready-made model with the desired voltage.
Video: The simplest battery charger
Remaking a laptop charger
However, you can do without searching for a transformer if you have an unnecessary laptop charger at hand - with a simple modification we will get a compact and lightweight pulse block power supply capable of charging car batteries. Since we need to get an output voltage of 14.1-14.3 V, no ready-made power supply will work, but the conversion is simple.
Let's look at the site standard scheme, according to which devices of this kind are assembled:
In them, maintaining a stabilized voltage is carried out by a circuit from the TL431 microcircuit that controls the 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, tells the PWM controller of the converter a signal to reduce the duty cycle of the supplied to the pulse transformer. Difficult? In fact, everything is easy to do with your own hands.
Having opened the charger, we find not far from the output connector TL431 and two resistors connected to the Ref. It is more convenient to adjust the upper arm of the divider (resistor R13 in the diagram): by decreasing the resistance, we reduce the voltage at the output of the charger; by increasing it, we raise it. If we have a 12 V charger, we will need a resistor with a higher resistance, if the charger is 19 V, then with a smaller one.
Video: Charging for car batteries. Protection against short circuit and reverse polarity. With your own hands
We unsolder the resistor and instead install a trimmer, pre-set on the multimeter to the same resistance. Then, having connected a load (a light bulb from a headlight) to the output of the charger, we turn it on to the network and smoothly rotate the trimmer motor, while simultaneously controlling the voltage. As soon as we get the voltage within 14.1-14.3 V, we disconnect the charger from the network, fix the trimmer resistor slide with nail polish (at least for nails) and put the case back together. It will take no more time than you spent reading this article.
There are also more complex stabilization schemes, and they can already be found in Chinese blocks. For example, here the optocoupler is controlled by the TEA1761 chip:
However, the setting principle is the same: the resistance of the resistor soldered between the positive output of the power supply and the 6th leg of the microcircuit changes. In the diagram shown, two parallel resistors are used for this (thus obtaining a resistance that is outside the standard series). We also need to solder a trimmer instead and set the output to required voltage. Here is an example of one of these boards:
By checking, we can understand that we are interested in the single resistor R32 on this board (circled in red) - we need to solder it.
There are often similar recommendations on the Internet on how to make a homemade charger from computer unit nutrition. But keep in mind that all of them are essentially reprints of old articles from the early 2000s, and such recommendations are not applicable to more or less modern power supplies. In them it is no longer possible to simply raise the 12 V voltage to the required value, since other output voltages are also controlled, and they will inevitably “float away” with such a setting, and the power supply protection will work. You can use laptop chargers that produce a single output voltage; they are much more convenient for conversion.
