For car batteries, since industrial samples are quite expensive. And you can make such a device yourself quite quickly, and from scrap materials that almost everyone has. From the article you will learn how to make chargers yourself at minimal cost. Two designs will be considered - with and without automatic control of the charge current.
The base of the charger is a transformer
In any charger you will find the main component - a transformer. It is worth noting that there are diagrams of devices built using a transformerless circuit. But they are dangerous because there is no protection against mains voltage. Therefore, you may receive an electric shock during manufacturing. Transformer circuits are much more efficient and simpler; they have galvanic isolation from the mains voltage. To make a charger you will need a powerful transformer. It can be found by disassembling an unusable microwave oven. However, spare parts from this electrical appliance can be used to make a battery charger with your own hands.
Old tube TVs used transformers TS-270, TS-160. These models are perfect for constructing a charger. It turns out to be even more effective to use them, since they already have two windings of 6.3 volts each. Moreover, they can collect current up to 7.5 amperes. And when charging a car battery, a current equal to 1/10 of the capacity is required. Therefore, with a battery capacity of 60 Ah, you need to charge it with a current of 6 amperes. But if there are no windings that satisfy the condition, you will need to make one. And now about how to make a homemade charger for a car as quickly as possible.
Transformer rewinding
So, if you decide to use a converter from a microwave oven, then you need to remove the secondary winding. The reason lies in the fact that these step-up transformers convert the voltage to a value of about 2000 volts. The magnetron requires a power supply of 4000 volts, so a doubling circuit is used. You won’t need such values, so mercilessly get rid of the secondary winding. Instead, wind a wire with a cross-section of 2 square meters. mm. But you don’t know how many turns are needed? This needs to be found out; you can use several methods. And this must be done when making a battery charger with your own hands.
The simplest and most reliable is experimental. Wind ten turns of the wire you will use. Clean its edges and plug in the transformer. Measure the voltage on the secondary winding. Let's say these ten turns produce 2 V. Therefore, 0.2 V (a tenth part) is collected from one turn. You need at least 12 V, and it is better if the output has a value close to 13. Five turns will give one volt, now you need 5*12=60. The desired value is 60 turns of wire. The second method is more complicated; you will have to calculate the cross-section of the transformer's magnetic core, you need to know the number of turns of the primary winding.
Rectifier block
We can say that the simplest homemade chargers for car batteries consist of two units - a voltage converter and a rectifier. If you do not want to spend a lot of time on assembly, then you can use a half-wave circuit. But if you decide to assemble the charger, as they say, conscientiously, then it is better to use the pavement. It is advisable to choose diodes whose reverse current is 10 amperes or higher. They usually have a metal body and a fastening with a nut. It is also worth noting that each semiconductor diode should be installed on a separate heatsink to improve cooling of its case.
Minor modernization
However, you can stop there, a simple homemade charger is ready for use. But it can be supplemented with measuring instruments. Having assembled all the components in a single case and securely fastened them in their places, you can start designing the front panel. You can place two instruments on it - an ammeter and a voltmeter. With their help, you can control the charging voltage and current. If desired, install an LED or incandescent lamp, which is connected to the output of the rectifier. With the help of such a lamp you will see whether the charger is plugged in. If necessary, add a small switch.
Automatic adjustment of charging current
Good results are shown by homemade chargers for car batteries that have an automatic current adjustment function. Despite their apparent complexity, these devices are very simple. True, some components will be required. The circuit uses current stabilizers, for example LM317, as well as its analogues. It is worth noting that this stabilizer has earned the trust of radio amateurs. It is trouble-free and durable, its characteristics are superior to domestic analogues.
In addition to it, you will also need an adjustable zener diode, for example TL431. All microcircuits and stabilizers used in the design must be mounted on separate radiators. The operating principle of the LM317 is that “extra” voltage is converted into heat. Therefore, if you have 15 V rather than 12 V coming from the rectifier output, then the “extra” 3 V will go into the radiator. Many homemade car battery chargers are made without strict outer casing requirements, but it is better if they are enclosed in an aluminum case.
Conclusion
At the end of the article, I would like to note that a device such as a car charger needs high-quality cooling. Therefore, it is necessary to provide for the installation of coolers. It is best to use those that are mounted in computer power supplies. Just pay attention to the fact that they need a power supply of 5 volts, not 12. Therefore, you will have to supplement the circuit by introducing a 5-volt voltage stabilizer into it. Much more can be said about chargers. The autocharger circuit is easy to repeat, and the device will be useful in any garage.
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 a 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.
Every owner of a used car is faced with the need to recharge the battery. In addition, batteries are often used as a backup (or main) source of electricity in a garage, barn, or country house without a centralized electricity supply.
To restore the battery charge, you can purchase a ready-made one; there is no shortage of options.
Used to charge car battery
However, many home craftsmen prefer to make their own. If you have a radio engineering background, you can calculate the circuit yourself. And for the majority of hobbyists who know how to hold a soldering iron in their hands, we offer a couple of simple designs.
First of all, let's decide which batteries you need to charge. As a rule, these are acid starter batteries used in cars.
Such a battery can be purchased inexpensively at a car store, or you can use an old one left over from replacing it in your car. a used one may not be able to work as a starter, but it’s easy to connect a lighting device (especially LED) or a radio in the country to it.
How to correctly calculate a homemade charger?
The first rule that needs to be learned is the value of the charge voltage.
Lead-acid batteries have an operating voltage of 12.5 volts. But to charge, you need to apply a voltage in the range of 13.9 - 14.4 volts. Accordingly, the charger must be made with exactly these output parameters.
The next quantity is power.
More precisely, the current strength at which there will be no voltage drop at the output terminals of the charger. If you do not plan to charge batteries with a capacity of more than 65 Ah, a stable current of 12 A is sufficient.
Important! This value must be provided by the output stage of the charger; the current at the 220 volt input will be several times less.
A low-power charger can also charge high-capacity batteries. It will just take much more time.
It would also be useful to have a function to automatically stop operation when a normal charge level is reached, to protect the device from reverse current (the battery is a powerful source of energy that can damage the output stage of an incorrectly designed charger), or at least control the output voltage, and better yet, the current.
If, in addition to the fuse, you install protection against polarity reversal and short circuit, great. However, any modification complicates the device and increases its cost.
The vehicle's on-board network is powered by the battery until the power plant starts. But it itself does not generate electrical energy. The battery is simply a container for electricity, which is stored in it and, if necessary, given to consumers. Afterwards, the expended energy is restored due to the operation of the generator, which produces it.
But even constant recharging of the battery from a generator is not able to completely restore the expended energy. This requires periodic charging from an external source rather than a generator.
Design and principle of operation of the charger
Chargers are used to produce. These devices operate from a 220 V network. In fact, the charger is a conventional electrical energy converter.
It takes the alternating current of the 220 V network, lowers it and converts it into direct current with a voltage of up to 14 V, that is, to the voltage that the battery itself produces.
Nowadays a large number of all kinds of chargers are produced - from primitive and simple ones to devices with a large number of various additional functions.
Chargers are also sold, which, in addition to possibly recharging the battery installed on the car, can also start the power plant. Such devices are called charging and starting devices.
There are also autonomous charging and starting devices that can recharge the battery or start the engine without connecting the device itself to a 220 V network. Inside such a device, in addition to equipment that converts electrical energy, there is also one, which makes such a device autonomous, although the battery of the device is also After each release of electricity, charging is required.
Video: How to make a simple charger
As for conventional chargers, the simplest of them consists of only a few elements. The main element of such a device is a step-down transformer. It lowers the voltage from 220 V to 13.8 V, which is the most optimal for charging the battery. However, the transformer only lowers the voltage, but converting it from alternating current to direct current is performed by another element of the device - a diode bridge, which rectifies the current and divides it into positive and negative poles.
Behind the diode bridge, an ammeter is usually included in the circuit, which shows the current strength. The simplest device uses a dial ammeter. In more expensive devices, it can be digital; in addition to the ammeter, a voltmeter can also be built-in. Some chargers have the ability to select voltage; for example, they can charge both 12-volt and 6-volt batteries.
Wires with “positive” and “negative” terminals come out of the diode bridge, which connect the device to the battery.
All this is enclosed in a housing, from which comes a wire with a plug for connecting to the network, and wires with terminals. To protect the entire circuit from possible damage, a fuse is included in it.
In general, this is the entire circuit of a simple charger. Charging the battery is relatively simple. The terminals of the device are connected to the discharged battery, but it is important not to mix up the poles. The device is then connected to the network.
At the very beginning of charging, the device will supply voltage with a current of 6-8 amperes, but as charging progresses, the current will decrease. All this will be displayed on the ammeter. If the battery is fully charged, the ammeter needle will drop to zero. This is the entire process of charging the battery.
The simplicity of the charger circuit makes it possible to manufacture it yourself.
Making your own car charger
Now let's look at the simplest chargers that you can make yourself. The first will be a device that is very similar in concept to the one described.
The diagram shows:
S1 - power switch (toggle switch);
FU1 - 1A fuse;
T1 - transformer TN44;
D1-D4 - diodes D242;
C1 - capacitor 4000 uF, 25 V;
A - 10A ammeter.
So, to make a homemade charger you will need a step-down transformer TS-180-2. Such transformers were used on old tube TVs. Its feature is the presence of two primary and secondary windings. Moreover, each of the secondary output windings has 6.4 V and 4.7 A. Therefore, in order to achieve the 12.8 V required for charging the battery, which this transformer is capable of, you need to connect these windings in series. For this, a short wire with a cross-section of at least 2.5 mm is used. sq. The jumper connects not only the secondary windings, but also the primary ones.
Video: The simplest battery charger
Next, you will need a diode bridge. To create it, 4 diodes are taken, designed for a current of at least 10 A. These diodes can be fixed on a textolite plate, and then they can be connected correctly. Wires are connected to the output diodes, which the device will connect to the battery. At this point, the assembly of the device can be considered complete.
Now about the correctness of the charging process. When connecting a device to a battery, do not reverse the polarity, otherwise you can damage both the battery and the device.
When connecting to a battery, the device must be completely de-energized. You can turn it on only after connecting it to the battery. It should also be disconnected from the battery after disconnecting from the network.
A heavily discharged battery cannot be connected to the device without a means that reduces the voltage and current, otherwise the device will supply a high current to the battery, which can damage the battery. An ordinary 12-volt lamp, which is connected to the output terminals in front of the battery, can act as a reducing agent. The lamp will light up when the device is operating, thereby partially absorbing the voltage and current. Over time, after the battery is partially charged, the lamp can be removed from the circuit.
When charging, you need to periodically check the state of charge of the battery, for which you can use a multimeter, voltmeter or load plug.
A fully charged battery, when checking its voltage, should show at least 12.8 V; if the value is lower, further charging is required to bring this indicator to the desired level.
Video: DIY car battery charger
Since this circuit does not have a protective housing, you should not leave the device unattended during operation.
And even if this device does not provide the optimal 13.8 V output, it is quite suitable for recharging the battery, although after about two years of using the battery, you will still need to charge it with a factory device that provides all the optimal parameters for charging the battery.
Transformerless charger
An interesting design is the circuit of a homemade device that does not have a transformer. Its role in this device is played by a set of capacitors designed for a voltage of 250 V. There must be at least 4 such capacitors. The capacitors themselves are connected in parallel.
A resistor is connected in parallel to the set of capacitors, designed to suppress the residual voltage after disconnecting the device from the network.
Next, you will need a diode bridge to operate with a permissible current of at least 6 A. It is connected to the circuit after a set of capacitors. And then the wires that will connect the device to the battery are connected to it.
Even with a fully operational car, sooner or later a situation may arise when you need an external source - a long parking period, side lights accidentally left on, and so on. Owners of old equipment are well aware of the need to regularly recharge the battery - this is due to the self-discharge of a “tired” battery and increased leakage currents in electrical circuits, primarily in the diode bridge of the generator.
You can purchase a ready-made charger: they Available in many variants and are easily accessible. But some may think that making a charger for a car battery with their own hands will be more interesting, while for others the ability to make a charger literally from scrap material will help them out.
Semiconductor diode + light bulb
It is not known who first came up with the idea of charging the battery in this way, but this is exactly the case when you can charge the battery literally with improvised means. In this circuit, the current source is a 220V electrical network, a diode is needed to convert alternating current into pulsating direct current, and the light bulb serves as a current-limiting resistor.
The calculation of this charger is as simple as its circuit:
- The current flowing through the lamp is determined based on its power as I=P/U, Where U– network voltage, P– lamp power. That is, for a 60 W lamp, the current in the circuit will be 0.27 A.
- Since the diode cuts off every second half-wave of the sinusoid, the real average load current, taking this into account, will be equal to 0.318*I.
As you can see, even when using a powerful lamp, the load current is small, which will allow the use of any common diode, for example 1N4004 (these usually come with alarm systems, are found in power supplies for low-power equipment, and so on). All you need to know to assemble such a device is that the stripe on the diode body indicates its cathode. Connect this contact to the positive terminal of the battery.
Do not connect this device to the battery unless it is removed from the vehicle to avoid high voltage damage to the on-board electronics!A similar manufacturing option is shown in the video
Rectifier
This memory is somewhat more complicated. This scheme is used in the cheapest factory devices:
To make a charger, you will need a mains transformer with an output voltage of at least 12.5 V, but not more than 14. Often a Soviet transformer of the TS-180 type is taken from tube TVs, which has two filament windings for a voltage of 6.3 V. When they are connected in series (the purpose of the terminals is indicated on the transformer body) we get exactly 12.6 V. A diode bridge (full-wave rectifier) is used to rectify the alternating current from the secondary winding. It can either be assembled from individual diodes (for example, D242A from the same TV), or you can buy a ready-made assembly (KBPC10005 or its analogues).
The rectifier diodes will heat up noticeably, and you will have to make a radiator for them from a suitable aluminum plate. In this regard, using a diode assembly is much more convenient - the plate is attached with a screw to its central hole using thermal paste.
Below is a diagram of the pin assignments of the TL494 microcircuit, the most common in switching power supplies:
We are interested in the circuit connected to pin 1. Looking through the traces connected to it on the board, find the resistor connecting this leg to the +12 V output. It is this that sets the output voltage of the 12-volt power supply circuit.
