Currently, there is no point in manufacturing a simple car battery charger according to the scheme. Many stores sell ready-made options with reasonable prices. However, it is still more pleasant to do something with your own hands. In addition, you can use improvised means, and the final cost will seem miserable.
At the same time, it is worth noting that the circuits, in the absence of precise adjustment of the current and voltage at the output, which do not have a current cutoff at the end of the charge, are relevant only for lead-acid batteries. Applying homemade devices to AGM batteries or gel batteries usually ends up damaging them.
The simplest scheme
The simplest assembly scheme for a car battery charger includes transformers. And most importantly, sheassembled from available components. But professional factory counterparts are designed in a similar way. And, despite all the primitiveness of a home-made device, it is quite efficient.
In addition, such a charge has a rather high efficiency, and during operation it is not capable of generating heat. In addition, the device has a stable current, regardless of the charge and supply fluctuations. In addition, there is short circuit protection.
Required tooling
To assemble a simple car battery charger with your own hands, you will need a TH61-22 transformer with a series connection of the windings. Its efficiency is not lower than 0.8, and the current strength does not exceed 6 A. The secondary winding of the transformer must produce a voltage of no more than 20 volts with a current strength of 8 amperes. If the finished part could not be found, then you can use any other transformer, in which you can rewind the secondary winding to obtain the required output current characteristics.
You will also need other accessories:
- MBGCH series capacitors, able to work with alternating voltage of 350 V (not less).
- Diodes capable of withstanding a current load of 10 A.
- Voltage changer.
As for the last point, in this case, you can use an ammeter that can work with direct current.
Or use the electromagnetic headlike M24.
Step by step assembly process
You can make a homemade battery charger with your own hands according to the following instructions:
- To begin with, a circuit is selected that will be implemented - in this case, a capacitor.
- Now you should choose a case of suitable dimensions, where the board with all the necessary details will be conveniently located. You can even opt for a milliammeter case.
- The transformer is mounted on an aluminum plate, which, in turn, is fixed in the housing.
- A textolite plate is placed inside the case, on which capacitors, relays and other parts are placed.
- Now it is worth fixing the voltage regulator and the leads for the terminals on the case.
- A massive aluminum radiator is placed outside to cool the power diodes. In addition, you need a fuse and a plug to supply current.
- All parts must be connected according to the scheme.
- Wires with fixed "crocodiles", which come from the charger and are intended for connection to the battery, must be with a cross section of at least 1 mm2.
Most homemade devices cannot boast of high efficiency, up to 90%. But, on the other hand, they are simple, and this makes purchased analogues no less reliable. In addition, they cope with their task.
If you wish, you can use a more complex scheme with a set of additional options. Such chargers are capable of operating in different modes, including automatic. They may also haveprotection systems against overheating and overcharging of the battery.
The simplest transistor charger
At the same time, you can do without a winding at all, supplementing the circuit with an electronic voltage regulator, placing it on the output. Such a scheme will be relevant in the conditions of garage use, since it is possible to adjust the charge current in case of voltage drops.
The composite transistor KT814-KT837 acts as a regulator here, the variable resistor will regulate the output. During the assembly process, instead of the zener diode 1N 754A, you can use the Soviet analogue D814A.
Such a circuit with electronic adjustment is assembled by surface mounting, where there is no need for etching of the printed circuit board. At the same time, it should be borne in mind that field-effect transistors should be placed on a heatsink that will heat up noticeably.
For this reason, it is optimal to take a computer cooler, which usually cools the processor. Its fan is connected to the outputs of the battery charger. The power of the resistor R1 should be 5 watts, no less. It can be wound from nichrome or fechral, or connected in parallel with 10 resistors of 1 W (10 ohms). The resistor can not be included at all in the circuit of the simplest charger, just do not forget that its presence allows you to protect the transistors when the wires are shorted.
When choosing a transformer, you should focus on the output voltage - 12, 6-16 V. You can pick up a local part that hasconnect two windings in parallel. As a last resort, look for a finished device with the required potential difference.
Homemade thyristor device
Those home craftsmen who are afraid to hold a soldering iron in their hands can be advised to assemble a battery charger with a smooth adjustment of the charge current. At the same time, such a circuit is devoid of the disadvantages that are inherent in the resistor analog.
In this case, the regulator is not a heat dissipator (usually a powerful rheostat is used in this capacity), but an electronic key on a thyristor. In this case, the entire load is perceived by this semiconductor element. And since a simple thyristor charger circuit is designed for a current of 10 A, such a device can replenish the energy of a battery with a capacity of up to 90 A / h. And by adjusting the degree of opening of the transition on the transistor VT1 by the resistor R5, smooth and very accurate control of the trinistor VS1 is provided.
Despite the simplicity of the circuit, it is reliable, it is easy to assemble and configure. At the same time, there is one important condition for ensuring the correct operation of a home-made device of this type. We are talking about the power of the transformer, which should be with a threefold margin for the charge current. In other words, with an upper limit of 10 A, the parameter should be at least 450-500 W.
It is worth noting that the resulting construction will differ in its massiveness. However, as a stationarycar battery charger such a scheme is quite acceptable.
A simple circuit for a switching charger
If there is no desire to search for a transformer or remake it, then you can pay attention to another option. If an unnecessary laptop charger is lying around on the farm, you should obviously not throw it away, since this is a good option for creating a switching power supply for the battery.
Since the output voltage should not exceed 14.1-14.3 V, then any ready-made block is not suitable for this. However, it can be reworked.
As a rule, in such devices, stabilizing power is maintained by a circuit that includes the following elements:
- circuit TL431;
- control optocoupler.
As soon as the output voltage exceeds the allowable limits (this is set by resistors), the microcircuit lights up the optocoupler LED. Thus, the PWM controller receives a signal about the need to reduce the duty cycle of the pulses that are fed to the transformer.
At first glance, everything seems complicated, and it's not really clear how to make a simple charger. At the same time, the manufacture of such a device is within the power of every home master with a personal car.
Rebuilding the switching power supply
First, you should open the case, after which you should find the same TL431 chip. Now you need to pay attention to its output contact, near which there are two resistors (they are usually marked R12 and R13 in the diagrams), connected with the leg REF.
Optimally adjust the upper arm of the divider. By reducing the resistance, the voltage at the output of the charger also decreases. If the parameter is increased, then the potential difference will also increase. If the power supply is designed for 12 V, then you will need a resistor with a large resistance, and at 19 V - with a smaller one.
Now, from a simple car battery charger circuit, you should unsolder the selected resistor (R13) and place a trimmer in its place, which is pre-tuned to the same resistance. After that, it is necessary to give a load to the output of the charger (for example, connect a light bulb from the headlight). Connect to the network and smoothly rotate the “trimmer” engine and simultaneously control the voltage.
As soon as the required limits are reached (14, 1-14, 3 V), the power supply is disconnected from the mains, and the trimmer engine is fixed in the accepted position. Nail polish works well for this. Now it remains to assemble the body in the reverse order. As a result, it takes less time than reading this entire manual.
Unnecessary block of a desktop computer
In this case, the "production" of the battery charger is difficult. However, this option for assembling a charger with your own hands does not require deep knowledge in electronics. In addition, the basis is already there - an old unnecessary power supply from a stationary computer, which is still functional.
Usually they give +5 V output voltageand +12 V with a current strength of about 2 A. These parameters are quite enough to assemble a low-power device that will faithfully serve the owner of the vehicle for many years.
Full charging of the battery will take a certain amount of time, and a lot of it. It mainly depends on the capacity of the battery. However, the use of such a homemade device will avoid the effect of plate desulfation.
Assembly process
Directly, the assembly process of a simple charger circuit, which will be carried out at home (or in the garage), may look like this:
- Open the case and remove all wires except for the green one. Only pre-mark or remember the connection points of black (GND) and yellow (+12 V).
- The green wire is soldered to the place where the black one was. This is to ensure that the unit starts up without a PC motherboard. Next, in place of soldering the black wire, put a tap for the negative wire of the battery. In the place where the yellow wire was, the positive battery charging contact is soldered.
- Find the TL 494 chip (or its equivalent). With all the variety of computer power supplies, these elements cannot be dispensed with.
- From the first leg of the microcircuit (usually the lower left one), you should find a resistor connected to the output +12 (yellow wire).
- The found resistor is soldered, after which its parameter is measured by the tester. Choose a variable resistor close toat par, and set the desired resistance. Now you can solder the element instead of the removed resistor with flexible wires.
- Start the power supply and adjust the variable transistor to get the desired output voltage - no more than 14, 3. The main thing here is not to overdo it because the limit is 15 V and the device simply turns off.
- Remove a variable resistor from a simple charger circuit, save the setting and measure the resulting resistance. Now it remains to choose a resistor with the received value (one or more) and solder it into the circuit.
- Check the power supply for issuing the required voltage. After that, it remains to assemble the case in the reverse order. As an additional option, you can connect a voltmeter to the outputs ("+" and "-"), placing it on the case for clarity.
The resulting device is sufficiently reliable and quite capable of replacing factory counterparts.
However, when using such a device, one should not forget that it is equipped with overload protection, but this does not save if the polarity is not observed. In other words, it is only necessary to confuse the plus with the minus when connecting the charger to the battery (which happens, although infrequently), it will fail instantly!
Helpful recommendation
If the simplest battery charger circuit is not equipped with automatic battery charge control, you should use the simplest network daily relay from Chinese manufacturers. As a result, you can not keep track of timedisconnecting the unit from the mains.
The cost of such a device usually does not exceed 200 rubles. Knowing the amount of time it takes to charge the battery, you can, by setting the required shutdown time, calmly go about your business.
The need for a timely shutdown of electricity supply is due to the fact that if you completely forget about charging the battery, this threatens with serious consequences:
- electrolyte boiling;
- breaking plates;
- battery failure.
But a new battery costs significantly more than the total investment in a homemade charger!
Terms of use
The main drawback of almost any simple 12 volt battery charger is the inability to turn off the device after it is fully charged. However, we have already considered how to fix this nuance, but this still does not make it easier. There are other features that are not available during the use of factory counterparts.
One of the important nuances is that the procedure for checking the memory "for a spark" is strictly prohibited! In addition, you must carefully monitor the connection of the charger to the battery, so as not to reverse the polarity in any case. Otherwise, it threatens with a complete failure of the memory.
And, most importantly, the connection to the terminals should only be made in the off state.
Safety
When making a homemade charge, do not forget about the elementary rulessafety instructions:
- All appliances, without exception, must be placed on a fireproof surface, including the battery.
- Primary use of charging should be carried out with full control of all parameters. It is necessary to ensure control over the heating temperature of all elements of the charger and battery. Electrolyte boiling should be avoided, voltage and current should be controlled by a tester. All this will allow you to determine the duration of a full charge of the battery, which will help in the future.
It's not a problem to independently assemble a charger for a car battery using a simple scheme. The main thing is to observe safety precautions. After all, you have to deal with a dangerous voltage of 220 V!
