Homemade battery chargers usually have very simple design, and in addition, increased reliability precisely due to the simplicity of the circuit. Another advantage of making a charger yourself is the relative cheapness of the components and, as a result, the low cost of the device.
Why is a prefabricated structure better than a store-bought one?
The main task of such equipment is to maintain the charge of the car battery at the required level if necessary. If the battery discharge occurs near the house where there is the necessary device, then there will be no problems. Otherwise, when there is no suitable equipment to power the battery, and the funds are also insufficient, you can assemble the device yourself.
The need to use auxiliary means to recharge a car battery is primarily due to low temperatures in the cold season, when a half-discharged battery is a major and sometimes completely unsolvable problem unless the battery is recharged in time. Then homemade chargers for power supply car batteries will be a salvation for users who do not plan to invest in such equipment, at least at the moment.
Operating principle
Up to a certain level, a car battery can receive power from the vehicle itself, or more precisely, from an electric generator. After this node, a relay is usually installed, responsible for setting the voltage to no more than 14.1V. In order for the battery to be charged to its maximum, a higher value of this parameter is required - 14.4V. Accordingly, batteries are used to implement such a task.
The main components of this device are a transformer and a rectifier. As a result, a direct current with a voltage of a certain value (14.4V) is supplied to the output. But why is there a run-up with the voltage of the battery itself - 12V? This is done in order to ensure the ability to charge a battery that has been discharged to a level where the value of this battery parameter was equal to 12V. If charging is characterized by the same parameter value, then powering the battery will become a difficult task.
Watch the video, the simplest device for charging a battery:
But there is a nuance here: a slight excess of the battery voltage level is not critical, while a significantly increased value of this parameter will have a very bad effect on the performance of the battery in the future. The operating principle that distinguishes any, even the simplest car battery charger, is to increase the resistance level, which will lead to a decrease in the charging current.
Accordingly, the higher the voltage value (tends to 12V), the lower the current. For normal operation of the battery, it is advisable to set a certain amount of charge current (about 10% of the capacity). In a hurry, it is tempting to change the value of this parameter to a higher value, however, this is fraught with negative consequences for the battery itself.
What is required to make a battery?
The main elements of a simple design: a diode and a heater. If you connect them correctly (in series) to the battery, you can achieve what you want - the battery will be charged in 10 hours. But for those who like to save electricity, this solution may not be suitable, because the consumption in this case will be about 10 kW. The operation of the resulting device is characterized by low efficiency.
Basic elements of a simple design
But to create a suitable modification, you will have to slightly modify individual elements, in particular, the transformer, the power of which should be at the level of 200-300 W. If you have old equipment, this part from a regular tube TV will do. To organize the ventilation system, a cooler will be useful; it is best if it comes from a computer.
When creating a simple charger for powering a battery with your own hands, the main elements are also a transistor and a resistor. To make the structure work, you will need a compact externally, but quite capacious metal case; a good option is a stabilizer box.
In theory, even a novice radio amateur who has not previously encountered complex circuits can assemble this kind of equipment.
Scheme simple device to charge the battery
The main difficulty lies in the need to modify the transformer. At this level of power, the windings are characterized by low voltage levels (6-7V), the current will be equal to 10A. Typically, a voltage of 12V or 24V is required, depending on the type of battery. To obtain such values at the output of the device, it is necessary to provide a parallel connection of the windings.
Step by step assembly
A homemade charger for powering a car battery begins with preparing the core. Winding the wire onto the windings is done with maximum compaction; it is important that the turns fit tightly to each other and there are no gaps left. We must not forget about the insulation, which is installed at intervals of 100 turns. The wire cross-section of the primary winding is 0.5 mm, the secondary winding is from 1.5 to 3.0 mm. If we consider that at a frequency of 50 Hz, 4-5 turns can provide a voltage of 1V, respectively, to obtain 18V, about 90 turns are required.
Next, a diode of suitable power is selected to withstand the loads applied to it in the future. The best option is a car generator diode. To eliminate the risk of overheating, it is necessary to ensure effective air circulation inside the housing of such a device. If the box is not perforated, you should take care of this before starting assembly. The cooler must be connected to the charger output. Its main task is to cool the diode and winding of the transformer, which is taken into account when choosing an area for installation.
Let's watch the video, detailed instructions for production:
The circuit of a simple charger for powering a car battery also contains a variable resistor. For normal charging operation, it is necessary to obtain a resistance of 150 Ohms and a power of 5 W. The KU202N resistor model meets these requirements more than others. You can choose a different option from this, but its parameters should be similar in value to those indicated. The resistor's job is to regulate the voltage at the device's output. Transistor model KT819 is also the best option from a number of analogues.
Efficiency assessment, cost
As you can see, if you need to assemble a homemade charger for a car battery, its circuit is more than simple to implement. The only difficulty is the arrangement of all the elements and their installation in the housing with subsequent connection. But such work can hardly be called labor-intensive, and the cost of all the parts used is extremely low.
Some of the parts, and perhaps all of them, will probably be found at home by a radio amateur, for example, a cooler from an old computer, a transformer from a tube TV, an old housing from a stabilizer. As for the degree of effectiveness, then similar devices, assembled with your own hands, do not have very high efficiency, however, as a result, they still cope with their task.
Let's watch the video, useful tips specialist:
Thus, large investments in creating a homemade charger are not required. On the contrary, all the elements cost extremely little, which makes this solution stand out compared to a device that can be purchased ready-made. The scheme discussed above is not highly efficient, but its main advantage is a charged car battery, albeit after 10 hours. You can improve this option or consider many others proposed for implementation.
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, indicating 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 a fully charged car battery, it is usually equal to - 14.4 V.
You can download the diagram here -
Printed circuit board
How to do printed circuit board, you decide. 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.
How does the battery charge? Is the circuit of this device complicated or not, in order to make the device with your own hands? Is it fundamentally different from what is used for mobile phones? We will try to answer all the questions posed further in the article.
General information
The battery plays a very important role in the functioning of devices, units and mechanisms that require electricity to operate. So, in vehicles it helps start the car engine. And in mobile phones batteries allow us to make calls.
Charging a battery, the circuit and principles of operation of this device are discussed even in a school physics course. But, alas, by the time they graduate, much of this knowledge is forgotten. Therefore, we hasten to remind you that the battery’s operation is based on the principle of a voltage difference (potential) between two plates, which are specially immersed in an electrolyte solution.
The first batteries were copper-zinc. But since then they have improved and modernized significantly.
How does a battery work?
The only visible element of any device is the case. It provides commonality and integrity to the design. It should be noted that the name “battery” can be fully applied to only one battery cell (they are also called banks), and for the same standard 12 V car battery there are only six of them.
Let's return to the body. Strict demands are placed on him. So, it should be:
- resistant to aggressive chemicals;
- able to withstand significant temperature fluctuations;
- with good vibration resistance.
All these requirements are met by modern synthetic material - polypropylene. More detailed differences should only be highlighted when working with specific samples.
Principle of operation
We'll look at lead-acid batteries as an example.
When there is a load on the terminal, a chemical reaction begins to occur, which is accompanied by the release of electricity. Over time, the battery will drain. How is it restored? Is there a simple diagram?
Charging a battery is not difficult. It is necessary to carry out the reverse process - electricity is supplied to the terminals, chemical reactions occur again (pure lead is restored), which in the future will allow the use of the battery.
Also, during charging, the density of the electrolyte increases. This way the battery restores its original properties. The better the technology and materials used in manufacturing, the more charge/discharge cycles the battery can withstand.
What electrical circuits for charging batteries exist?
The classic device is made of a rectifier and transformer. If we consider all the same car batteries with a voltage of 12 V, then the chargers for them have DC approximately 14 V.
Why is this so? This voltage is necessary so that current can flow through a discharged car battery. If he himself has 12 V, then a device of the same power will not be able to help him, which is why they take higher values. But in everything you need to know when to stop: if you increase the voltage too much, it will have a detrimental effect on the service life of the device.
Therefore, if you want to make a device with your own hands, you need to look for suitable charging schemes for car batteries for cars. The same applies to other technology. If a charging circuit is needed, then a 4 V device is needed and no more.
Recovery process
Let's say you have a circuit for charging a battery from a generator, according to which the device was assembled. The battery is connected and the recovery process begins immediately. As it progresses, the devices will grow. The charging current will drop along with it.
When the voltage approaches the maximum possible value, this process practically does not occur at all. This indicates that the device has successfully charged and can be turned off.
It is necessary to ensure that the battery current is only 10% of its capacity. Moreover, it is not recommended to either exceed this figure or reduce it. So, if you follow the first path, the electrolyte will begin to evaporate, which will significantly affect the maximum capacity and operating time of the battery. On the second path, the necessary processes will not occur at the required intensity, which is why the negative processes will continue, although to a somewhat lesser extent.
Charger
The described device can be purchased or assembled with your own hands. For the second option we will need electrical circuits charging batteries. The choice of technology by which it will be made should depend on which batteries are the target. You will need the following components:
- (designed on ballast capacitors and a transformer). The higher the indicator can be achieved, the greater the current will be. In general, this should be enough for charging to work. But the reliability of this device is very low. So, if the contacts are broken or something is mixed up, then both the transformer and the capacitors will fail.
- Protection in case of connecting the “wrong” poles. To do this, you can construct a relay. So, the conditional connection is based on a diode. If you confuse plus and minus, it will not pass current. And since there is a relay connected to it, it will be de-energized. Moreover, this circuit can be used with a device based on both thyristors and transistors. It must be connected to the break in the wires with which the charging itself is connected to the battery.
- Automation that battery charging should have. The circuit in this case must ensure that the device will work only when it is really needed. To do this, resistors change the response threshold of the control diode. 12 V batteries are considered to be fully rated when their voltage is within 12.8 V. Therefore, this indicator is desirable for this circuit.
Conclusion
So we looked at what battery charging is. The circuit of this device can be made on a single board, but it should be noted that this is quite complicated. That's why they are made multi-layered.
Within the framework of the article, various circuit diagrams, which make it clear how batteries are actually charged. But you need to understand that these are only general images, and more detailed ones, with indications of the chemical reactions taking place, are special for each type of battery.
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 purchase or make my own charger. In the evening, after checking out the garage and finding a suitable transformer there, I decided to do the charging myself.
There, among the unnecessary junk, I also found a voltage stabilizer from an old TV, which, in my opinion, would work wonderfully as a housing.
Having scoured the vast expanses of the Internet and really assessed my strengths, I probably chose the most simple diagram.
After printing out the diagram, I went to a neighbor who is interested in radio electronics. Within 15 minutes, he collected the necessary parts for me, cut off a piece of foil PCB and gave me a marker for drawing circuit boards. Having spent about an hour, I drew an acceptable board (the dimensions of the case allow for spacious installation). I won’t tell you how to etch the board, there is a lot of information about this. I took my creation to my neighbor, and he etched it for me. In principle, you 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 displayed the pinout of the transistors 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 purchased 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 I soldered a diode bridge on a piece of PCB.
The thyristor must be installed on a radiator, since it gets noticeably hot during operation.
Separately, I must say about the ammeter. I had to buy it in a store, where the sales consultant also picked up the shunt. I decided to modify the circuit a little and add a switch so that I could measure the voltage on the battery. Here, too, a shunt was needed, but when measuring voltage, it is connected not in parallel, but in series. The calculation formula can be found on the Internet; I would add that the dissipation power of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but my 4-watt shunt was heating up. The reason is unknown to me, I don’t have enough experience in such matters, but having decided that I mainly needed the readings of an ammeter, and not a voltmeter, I decided on it. Moreover, in voltmeter mode the shunt noticeably warmed up within 30-40 seconds. So, having collected everything I needed and checked everything on the stool, I took up the body. Having completely disassembled the stabilizer, I took out all its contents.
Having marked the front wall, I drilled holes for the variable resistor and switch, then using a small diameter drill around the circumference I drilled holes for the ammeter. Sharp edges were finished with a file.
After racking my brains a bit over the location of the transformer and radiator with thyristor, I settled on this option.
I bought a couple more crocodile clips and everything is ready to charge. The peculiarity of this circuit is that it only works under load, so after assembling the device and not finding 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 a transformer with a voltage on the secondary winding of 20-24 volts. Zener diode D 814. All other elements are indicated in the diagram.
Many car enthusiasts know very well that in order to extend the life of the battery, it is required periodically from the charger, and not from the car’s generator.
And the longer the battery life, the more often it needs to be charged to restore charge.
You can't do without chargers
To perform this operation, as already noted, chargers operating from a 220 V network are used. There are a lot of such devices on the automotive market, they may have various useful additional functions.
However, they all do the same job - convert alternating voltage 220 V into direct voltage - 13.8-14.4 V.
In some models, the charging current is manually adjusted, but there are also models with fully automatic operation.
Of all the shortcomings of purchased chargers One can note their high cost, and the more sophisticated the device, the higher the price.
But many people have it at hand a large number of electrical appliances, the components of which may well be suitable for creating a homemade charger.
Yes, a homemade device will not look as presentable as a purchased one, but its task is to charge the battery, and not to “show off” on the shelf.
One of the most important conditions when creating a charger, this requires at least basic knowledge of electrical engineering and radio electronics, as well as the ability to hold a soldering iron in your hands and be able to use it correctly.
Memory from a tube TV
The first scheme will be, perhaps the simplest, and almost any car enthusiast can cope with it.
To make a simple charger, you only need two components - a transformer and a rectifier.
The main condition that the charger must meet is that the current output from the device must be 10% of the battery capacity.
That is, a 60 Ah battery is often used in passenger cars; based on this, the current output from the device should be 6 A. The voltage should be 13.8-14.2 V.
If someone has an old, unnecessary tube Soviet TV, then it is better to have a transformer than not to find one.
The schematic diagram of the TV charger looks like this.
Often, a TS-180 transformer was installed on such televisions. Its peculiarity was the presence of two secondary windings, 6.4 V each and a current strength of 4.7 A. The primary winding also consists of two parts.
First you need to do serial connection windings The convenience of working with such a transformer is that each of the winding terminals has its own designation.
To connect the secondary winding in series, you need to connect pins 9 and 9\’ together.
And to pins 10 and 10\’ - solder two pieces of copper wire. All wires that are soldered to the terminals must have a cross-section of at least 2.5 mm. sq.
As for the primary winding, for a series connection you need to connect pins 1 and 1\'. Wires with a plug for connecting to the network must be soldered to pins 2 and 2\’. At this point, work with the transformer is completed.
The diagram shows how the diodes should be connected - the wires coming from pins 10 and 10\', as well as the wires that will go to the battery, are soldered to the diode bridge.
Don't forget about fuses. It is recommended to install one of them on the “positive” terminal of the diode bridge. This fuse must be rated for a current of no more than 10 A. The second fuse (0.5 A) must be installed at terminal 2 of the transformer.
Before starting charging, it is better to check the functionality of the device and check its output parameters using an ammeter and voltmeter.
Sometimes it happens that the current is slightly higher than required, so some install a 12-volt incandescent lamp with a power of 21 to 60 watts in the circuit. This lamp will “take away” the excess current.
Microwave oven charger
Some car enthusiasts use a transformer from a broken microwave oven. But this transformer will need to be redone, since it is a step-up transformer, not a step-down transformer.
It is not necessary that the transformer be in good working order, since the secondary winding in it often burns out, which will still have to be removed during the creation of the device.
Remaking the transformer comes down to completely removing the secondary winding and winding a new one.
An insulated wire with a cross-section of at least 2.0 mm is used as a new winding. sq.
When winding, you need to decide on the number of turns. You can do this experimentally - wind 10 turns of a new wire around the core, then connect a voltmeter to its ends and power the transformer.
According to the voltmeter readings, it is determined what output voltage these 10 turns provide.
For example, measurements showed that there is 2.0 V at the output. This means that 12V at the output will provide 60 turns, and 13V will provide 65 turns. As you understand, 5 turns adds 1 volt.
It is worth pointing out that it is better to assemble such a charger with high quality, then place all the components in a case that can be made from scrap materials. Or mount it on a base.
Be sure to mark where the “positive” wire is and where the “negative” wire is, so as not to “over-plus” and damage the device.
Memory from the ATX power supply (for prepared ones)
A charger made from a computer power supply has a more complex circuit.
For the manufacture of the device, units with a power of at least 200 Watts of the AT or ATX models, which are controlled by a TL494 or KA7500 controller, are suitable. It is important that the power supply is fully operational. The ST-230WHF model from old PCs performed well.
A fragment of the circuit diagram of such a charger is presented below, and we will work on it.
In addition to the power supply, you will also need a potentiometer-regulator, a 27 kOhm trim resistor, two 5 W resistors (5WR2J) and a resistance of 0.2 Ohm or one C5-16MV.
The initial stage of work comes down to disconnecting everything unnecessary, which are the “-5 V”, “+5 V”, “-12 V” and “+12 V” wires.
The resistor indicated in the diagram as R1 (it supplies a voltage of +5 V to pin 1 of the TL494 controller) must be unsoldered, and a prepared 27 kOhm trimmer resistor must be soldered in its place. The +12 V bus must be connected to the upper terminal of this resistor.
Pin 16 of the controller should be disconnected from the common wire, and you also need to cut the connections of pins 14 and 15.
IN back wall In the power supply housing, you need to install a potentiometer-regulator (R10 in the diagram). It must be installed on an insulating plate so that it does not touch the block body.
The wiring for connecting to the network, as well as the wires for connecting the battery, should also be routed through this wall.
To ensure ease of adjustment of the device, from the existing two 5 W resistors on a separate board, you need to make a block of resistors connected in parallel, which will provide an output of 10 W with a resistance of 0.1 Ohm.
Then you should check the correct connection of all terminals and the functionality of the device.
The final work before completing the assembly is to calibrate the device.
To do this, the potentiometer knob should be set to the middle position. After this, the open circuit voltage should be set on the trimmer resistor at 13.8-14.2 V.
If everything is done correctly, then when the battery starts charging, a voltage of 12.4 V with a current of 5.5 A will be supplied to it.
As the battery charges, the voltage will increase to the value set on the trim resistor. As soon as the voltage reaches this value, the current will begin to decrease.
If all operating parameters converge and the device operates normally, all that remains is to close the housing to prevent damage to the internal elements.
This device from the ATX unit is very convenient, because when the battery is fully charged, it will automatically switch to voltage stabilization mode. That is, recharging the battery is completely excluded.
For convenience of work, the device can be additionally equipped with a voltmeter and ammeter.
Bottom line
These are just a few types of chargers that can be made at home from improvised materials, although there are many more options.
This is especially true for chargers that are made from computer power supplies.
If you have experience in making such devices, share it in the comments, many would be very grateful for it.
