Not every car owner has a charger for a car battery. Many people do not consider it necessary to purchase such a unit, believing that they will not need it. However, as practice shows, at least once in his life every driver finds himself in a situation where he needs to drive, but...
It is not necessary to purchase a new factory charger; you can make one yourself from, for example, old electrical appliances. There are many options for creating your own car chargers, but most of them have significant drawbacks.
The video shows the creation of a car charger:
In the case when all the elements are in working order and the assembly occurred without errors, the circuit should work immediately. And the car owner only needs to set the voltage threshold using a resistor. When charging reaches this device, it will switch to low current mode.
Adjustment is carried out at the time of charging. But it’s probably better to insure yourself: set up and test protection and regulation schemes. For this purpose, you will need a multimeter or a tester designed to work with constant voltage.
There are certain rules that must be followed when using a homemade car charger.
It is important, even before charging, to clean it of dust and dirt. Then wipe with a soda solution to remove acid residues. If there are acid particles on the battery, the soda will begin to foam.
The plugs for filling acids in the battery must be unscrewed. This is done so that the gases formed in the battery have the opportunity to escape. Then you should check the quantity: if the level is less than optimal, add distilled water.
After this, use the switch to set a certain charge current reading, connect the assembled device, taking into account the polarity. Accordingly, the positive charging terminal should be connected to the positive terminal of the battery. Keeping the switch in the lower position will cause the device's arrow to indicate the current voltage. The voltmeter begins to display current voltage at the same time.
If it has a capacity of 50 Ah and is currently 50% charged, then you should first set the current to 25 amperes, gradually reducing it to zero. Automatic charging devices operate on a similar principle. They help charge your car battery to 100%. True, such devices are very expensive. With timely charging, such an expensive device is not needed.
To summarize, we can say that, even using used parts from old devices, you can assemble a pretty decent charger for a car battery. If you don’t have the ability to do this yourself, then you can always find such a craftsman in every garage cooperative. And it will certainly cost significantly less than buying a new factory device.
Very often, especially in the cold season, car enthusiasts are faced with the need to charge a car battery. It is possible, and advisable, to purchase a factory charger, preferably a charging and starting one for use in the garage.
But, if you have electrical engineering skills and certain knowledge in the field of radio engineering, then you can make a simple charger for a car battery with your own hands. In addition, it is better to prepare in advance for the possible event that the battery suddenly discharges far from home or a place where it is parked and serviced.
Charging a car battery is necessary when the voltage drop across the terminals is less than 11.2 Volts. Despite the fact that the battery can start the car engine even with such a charge, during long-term parking at low voltages, plate sulfation processes begin, which lead to loss of battery capacity.
Therefore, when wintering a car in a parking lot or garage, it is necessary to constantly recharge the battery and monitor the voltage at its terminals. A better option is to remove the battery, put it in a warm place, but still do not forget about maintaining its charge.
The battery is charged using constant or pulsed current. In the case of charging from a constant voltage source, a charge current equal to one tenth of the battery capacity is usually selected.
For example, if the battery capacity is 60 Amp-hours, the charging current should be selected at 6 Amp. However, research shows that the lower the charge current, the less intense the sulfation processes.
Moreover, there are methods for desulfating battery plates. They are as follows. First, the battery is discharged to a voltage of 3 - 5 Volts with high currents of short duration. For example, such as when turning on the starter. Then there is a slow full charge with a current of about 1 Ampere. Such procedures are repeated 7-10 times. There is a desulfation effect from these actions.
Desulfating pulse chargers are practically based on this principle. The battery in such devices is charged with pulsed current. During the charging period (several milliseconds), a short discharge pulse of reverse polarity and a longer charging pulse of direct polarity are applied to the battery terminals.
It is very important during the charging process to prevent the effect of overcharging the battery, that is, the moment when it is charged to the maximum voltage (12.8 - 13.2 Volts, depending on the type of battery).
This can cause an increase in the density and concentration of the electrolyte, irreversible destruction of the plates. That is why factory chargers are equipped with an electronic control and shutdown system.
Let's consider the case of how to charge a battery using improvised means. For example, a situation when you left your car near your house in the evening, forgetting to turn off some electrical equipment. By morning the battery was discharged and would not start the car.
In this case, if your car starts well (with half a turn), it is enough to “tighten” the battery a little. How to do it? First, you need a constant voltage source ranging from 12 to 25 volts. Secondly, restrictive resistance.
What can you recommend?
Nowadays, almost every home has a laptop. The power supply of a laptop or netbook, as a rule, has an output voltage of 19 Volts and a current of at least 2 amperes. The external pin of the power connector is minus, the internal pin is positive.
As a limiting resistance, and it is mandatory!!!, you can use the car's interior light bulb. You can, of course, have more power from turn signals or even worse stops or dimensions, but there is a possibility of overloading the power supply. The simplest circuit is assembled: minus the power supply - light bulb - minus the battery - plus the battery - plus the power supply. In a couple of hours the battery will be charged enough to start the engine.
If you don’t have a laptop, you can pre-purchase a powerful rectifier diode on the radio market with a reverse voltage of more than 1000 Volts and a current of 3 Amperes. It is small in size and can be put in the glove compartment for an emergency.
What to do in an emergency?
Conventional lamps can be used as a limiting load incandescent at 220 Volt. For example, a 100 Watt lamp (power = voltage X current). Thus, when using a 100-watt lamp, the charge current will be about 0.5 Ampere. Not much, but overnight it will give 5 Amp-hours of capacity to the battery. Usually it is enough to crank the car starter a couple of times in the morning.
If you connect three 100-watt lamps in parallel, the charging current will triple. You can charge your car battery almost halfway overnight. Sometimes they turn on an electric stove instead of lamps. But here the diode may already fail, and at the same time the battery.
In general, this kind of experiments with direct charging of the battery from an alternating voltage network of 220 Volts extremely dangerous. They should only be used in extreme cases when there is no other option.
Before you start making your own charger for a car battery, you should evaluate your knowledge and experience in the field of electrical and radio engineering. In accordance with this, select the complexity level of the device.
First of all, you should decide on the element base. Very often, computer users are left with old system units. There are power supplies there. Along with the +5V supply voltage, they contain a +12 Volt bus. As a rule, it is designed for current up to 2 Amperes. This is quite enough for a weak charger.
Video - step-by-step manufacturing instructions and diagram of a simple charger for a car battery from a computer power supply:
But 12 volts is not enough. It is necessary to “overclock” it to 15. How? Usually using the "poke" method. Take a resistance of about 1 kiloOhm and connect it in parallel with other resistances near the microcircuit with 8 legs in the secondary circuit of the power supply.
Thus, the transmission coefficient of the feedback circuit changes, respectively, and the output voltage.
It’s difficult to explain in words, but usually users succeed. By selecting the resistance value, you can achieve an output voltage of about 13.5 Volts. This is enough to charge a car battery.
If you don’t have a power supply at hand, you can look for a transformer with a secondary winding of 12 - 18 Volts. They were used in old tube televisions and other household appliances.
Now such transformers can be found in used uninterruptible power supplies; they can be bought for pennies on the secondary market. Next, we begin manufacturing the transformer charger.
Transformer chargers are the most common and safe devices widely used in automotive practice.
Video - a simple charger for a car battery using a transformer:
The simplest circuit of a transformer charger for a car battery contains:
A large current flows through the limiting load and it gets very hot, so to limit the charging current, capacitors are often used in the primary circuit of the transformer.
In principle, in such a circuit you can do without a transformer if you choose the capacitor wisely. But without galvanic isolation from the AC network, such a circuit will be dangerous from the point of view of electric shock.
More practical are charger circuits for car batteries with regulation and limitation of the charge current. One of these schemes is shown in the figure:
You can use the rectifier bridge of a faulty car generator as powerful rectifier diodes by slightly reconnecting the circuit.
More complex pulse chargers with desulfation function are usually made using microcircuits, even microprocessors. They are difficult to manufacture and require special installation and configuration skills. In this case, it is easier to purchase a factory device.
Conditions that must be met when using a homemade car battery charger:
Video - diagram of a charger for a car battery from a UPS:
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Comments on the article:
Lyokha
The information presented here is certainly interesting and informative. As a former radio engineer of the Soviet school, I read it with great interest. But in reality, now even “desperate” radio amateurs are unlikely to bother searching for circuit diagrams for a homemade charger and later assembling it with a soldering iron and radio components. Only radio fanatics will do this. It’s much easier to buy a factory-made device, especially since the prices, I think, are affordable. As a last resort, you can turn to other car enthusiasts with a request to “light up”, fortunately, now there are plenty of cars everywhere. What is written here is useful not so much for its practical value (although that too), but for instilling interest in radio engineering in general. After all, most modern children not only cannot distinguish a resistor from a transistor, but they won’t be able to pronounce it the first time. And this is very sad...
Michael
When the battery was old and half-dead, I often used a laptop power supply to recharge. As a current limiter I used an unnecessary old taillight with four 21-watt bulbs connected in parallel. I control the voltage at the terminals, at the beginning of charging it is usually about 13 V, the battery greedily eats up the charge, then the charging voltage increases, and when it reaches 15 V, I stop charging. It takes half an hour to an hour to reliably start the engine.
Ignat
I have a Soviet charger in my garage, it’s called “Volna”, made in ’79. Inside is a hefty and heavy transformer and several diodes, resistors and transistors. Almost 40 years in service, and this despite the fact that my father and brother use it constantly, not only for charging, but also as a 12 V power supply. And now, indeed, it’s easier to buy a cheap Chinese device for five hundred square meters than to bother with soldering iron And on Aliexpress you can even buy it for one and a half hundred, although it will take a long time to send it. Although I liked the option from the computer power supply, I have a dozen old ones lying around in the garage, but they work quite well.
San Sanych
Hmmm. Of course, the Pepsicol generation is growing... :-\ The correct charger should produce 14.2 volts. No more and no less. With a greater potential difference, the electrolyte will boil, and the battery will swell so that it will then be problematic to remove it or, conversely, not to install it back in the car. With a smaller potential difference, the battery will not charge. The most normal circuit presented in the material is with a step-down transformer (first). In this case, the transformer must produce exactly 10 volts at a current of at least 2 amperes. There are plenty of these on sale. It is better to install domestic diodes - D246A (must be installed on a radiator with mica insulators). At worst - KD213A (these can be glued to an aluminum radiator with superglue). Any electrolytic capacitor with a capacity of at least 1000 uF for an operating voltage of at least 25 volts. A very large capacitor is also not needed, since due to the ripples of the under-rectified voltage we obtain the optimal charge for the battery. In total we get 10 * root of 2 = 14.2 volts. I myself have had such a charger since the days of the 412th Muscovite. Not killable at all. 🙂
Kirill
In principle, if you have the necessary transformer, it is not so difficult to assemble a transformer charger circuit yourself. Even for me, not a very big specialist in the field of radio electronics. Many people say, why bother if it’s easier to buy. I agree, but this is not about the final result, but about the process itself, because it is much more pleasant to use something made with your own hands than something purchased. And most importantly, if this homemade product breaks down, then the one who assembled it knows his battery charger thoroughly and is able to fix it quickly. And if a purchased product burns out, then you still need to dig around and it’s not at all a fact that a breakdown will be found. I vote for self-built devices!
Oleg
In general, I think that the ideal option is an industrial charger, so I have one and carry it in the trunk all the time. But in life situations are different. Once I was visiting my daughter in Montenegro, and there they generally don’t carry anything with them and rarely do anyone even have one. So she forgot to close the door at night. The battery is drained. No diode at hand, no computer. I found a Boschevsky screwdriver with 18 volts and 1 ampere current. So I used his charger. True, I charged it all night and periodically checked for overheating. But she couldn’t stand it, in the morning they started her with half a kick. So there are many options, you have to look. Well, regarding homemade chargers, as a radio engineer I can only recommend transformer ones, i.e. isolated via the network, they are safe compared to capacitors, diodes with a light bulb.
Sergey
Charging the battery with non-standard devices can lead to either complete irreversible wear or a decrease in guaranteed operation. The whole problem is connecting homemade products, so that the rated voltage does not exceed the permissible one. It is necessary to take into account temperature changes and this is a very important point, especially in winter. When we decrease by a degree, we increase it and vice versa. There is an approximate table depending on the type of battery - it is not difficult to remember. Another important point is that all measurements of voltage and, of course, density are made only when the engine is cold, with the engine not running.
Vitalik
In general, I use the charger extremely rarely, maybe once every two or three years, and only when I go away for a long time, for example in the summer for a couple of months to the south to visit relatives. And so basically the car is in operation almost every day, the battery is charged and there is no need for such devices. Therefore, I think that buying for money something that you practically never use is not very smart. The best option is to assemble such a simple craft, say from a computer power supply, and let it lie around, waiting in the wings. After all, the main thing here is not to fully charge the battery, but to cheer it up a little to start the engine, and then the generator will do its job.
Nikolay
Just yesterday we recharged the battery using a screwdriver charger. The car was parked outside, the frost was -28, the battery was spun a couple of times and stopped. We took out a screwdriver, a couple of wires, connected it, and after half an hour the car started up safely.
Dmitriy
A ready-made store charger is of course an ideal option, but who wants to use their own hands, and considering that you don’t have to use it often, you don’t have to spend money on the purchase and do the charging yourself.
A homemade charger should be autonomous, not require supervision or current control, since we charge most often at night. In addition, it must provide a voltage of 14.4 V and ensure that the battery is turned off when the current and voltage exceed the norm. It should also provide protection against polarity reversal.
The main mistakes that “Kulibins” make are connecting directly to a household electrical network, this is not even a mistake, but a violation of safety regulations, the next limiting the charging current is by capacitors, and it’s also more expensive: one bank of capacitors 32 uF at 350-400 V (less than that is not possible) will cost like a cool branded charger.
The easiest way is to use a computer switching power supply (UPS), it is now more affordable than a hardware transformer, and you don’t need to do separate protection, everything is ready.
If you don't have a computer power supply, you need to look for a transformer. A power supply with filament windings from old tube TVs - TS-130, TS-180, TS-220, TS-270 - is suitable. They have plenty of power behind their eyes. You can find an old TN filament transformer at the car market.
But all this is only for those who are friends with electricians. If not, don’t bother - you won’t do the exercises that meet all the requirements, so buy ready-made ones and don’t waste time.
Laura
I got a charger from my grandfather. Since Soviet times. Homemade. I don’t understand this at all, but when my friends see it, they click their tongues in admiration and respect, saying, this is a thing “for centuries.” They say it was assembled using some lamps and still works. True, I practically don’t use it, but that’s not the point. Everyone criticizes Soviet technology, but it turns out to be many times more reliable than modern technology, even homemade ones.
Vladislav
In general, a useful thing in the household, especially if there is a function for adjusting the output voltage
Alexei
I’ve never had the opportunity to use or assemble homemade chargers, but I can quite imagine the principle of assembly and operation. I think that homemade products are no worse than factory ones, it’s just that no one wants to tinker, especially since store-bought ones are quite affordable.
Victor
In general, the schemes are simple, there are few parts and they are accessible. Adjustment can also be done if you have some experience. So it's quite possible to collect. Of course, it is very pleasant to use a device assembled with your own hands)).
Ivan
The charger is, of course, a useful thing, but now there are more interesting specimens on the market - their name is start-chargers
Sergey
There are a lot of charger circuits and as a radio engineer I have tried many of them. Until last year, I had a scheme that worked for me since Soviet times and it worked perfectly. But one day (through my fault) the battery completely died in the garage and I needed a cyclic mode to restore it. Then I didn’t bother (due to lack of time) with creating a new circuit, but just went and bought it. And now I carry a charger in the trunk just in case.
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.
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 disadvantages of purchased chargers, one can note their high cost, and the more sophisticated the device, the higher the price.
But many people have a large number of electrical appliances at hand, 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 a shelf.
One of the most important conditions when creating a charger is 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.
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 will need to connect the windings in series. 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.
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.
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.
You need to install a potentiometer-regulator in the rear wall of the power supply housing (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.
Often car owners have to deal with the phenomenon of the inability to start the engine due to a low battery. To solve the problem, you will need to use a battery charger, which costs a lot of money. In order not to spend money on buying a new charger for a car battery, you can make it yourself. It is only important to find a transformer with the necessary characteristics. To make a homemade device, you don’t have to be an electrician, and the whole process will take no more than a few hours.
Not all drivers know that lead-acid batteries are used in cars. Such batteries are distinguished by their endurance, so they can last up to 5 years.
To charge lead-acid batteries, a current equal to 10% of the total battery capacity is used. This means that to charge a battery with a capacity of 55 A/h, a charging current of 5.5 A is required. If a very high current is applied, this can lead to boiling of the electrolyte, which, in turn, will lead to a decrease in service life devices. A small charging current does not extend the life of the battery, but it does not have a negative impact on the integrity of the device.
This is interesting! When a current of 25 A is supplied, the battery is quickly recharged, so within 5-10 minutes after connecting a charger with this rating, you can start the engine. Such a high current is produced by modern inverter chargers, but it negatively affects the battery life.
When charging the battery, the charging current flows back to the working one. The voltage for each can should not be higher than 2.7 V. A 12 V battery has 6 cans that are not connected to each other. Depending on the battery voltage, the number of cells differs, as well as the required voltage for each cell. If the voltage is higher, this will lead to a process of decomposition of the electrolyte and plates, which contributes to the failure of the battery. To prevent the electrolyte from boiling, the voltage is limited to 0.1 V.
The battery is considered discharged if, when connecting a voltmeter or multimeter, the devices show a voltage of 11.9-12.1 V. Such a battery should be recharged immediately. A charged battery has a voltage at the terminals of 12.5-12.7 V.
Example of voltage at the terminals of a charged battery
The charging process is the restoration of spent capacity. Charging batteries can be done in two ways:
Now even an inexperienced driver can understand that if there is no need to rush into charging the battery, then it is better to give preference to the first option (in terms of current). With accelerated charge recovery, the service life of the device is reduced, so there is a high probability that you will need to buy a new battery in the near future. Based on the above, the material will consider options for manufacturing chargers based on current and voltage. For production, you can use any available devices, which we will discuss later.
Before carrying out the procedure for making a homemade battery charger, you must pay attention to the following requirements:
Polarity reversal is a dangerous process, as a result of which the battery may explode or boil. If the battery is in good condition and only slightly discharged, then if the charger is connected incorrectly, the charging current will increase above the rated one. If the battery is discharged, then when the polarity is reversed, an increase in voltage above the set value is observed and, as a result, the electrolyte boils.
Before you start developing a battery charger, it is important to understand that such a device is homemade and can negatively affect the battery life. However, sometimes such devices are simply necessary, as they can significantly save money on purchasing factory-made devices. Let's look at what you can make your own battery chargers from and how to do it.
This charging method is relevant in situations where you need to start a car on a dead battery at home. In order to do this, you will need the components to assemble the device and a 220 V alternating voltage source (socket). The circuit of a homemade charger for a car battery contains the following elements:
It is important! Before assembling such a circuit, you need to understand that there is always a risk to life, so you should be extremely careful and careful.
Connection diagram of a charger from a light bulb and a diode to a battery
The plug should be plugged into the socket only after the entire circuit has been assembled and the contacts have been insulated. To avoid the occurrence of short circuit current, a 10 A circuit breaker is included in the circuit. When assembling the circuit, it is important to take into account the polarity. The light bulb and semiconductor diode must be connected to the positive terminal circuit of the battery. When using a 100 W light bulb, a charging current of 0.17 A will flow to the battery. To charge a 2 A battery, you will need to charge it for 10 hours. The higher the power of the incandescent lamp, the higher the charging current.
It makes no sense to charge a completely dead battery with such a device, but recharging it in the absence of a factory charger is quite possible.
This option also falls into the category of the simplest homemade chargers. The basis of such a charger includes two main elements - a voltage converter and a rectifier. There are three types of rectifiers that charge the device in the following ways:
Rectifiers of the first option charge the battery exclusively with direct current, which is cleared of alternating voltage ripples. AC rectifiers apply pulsating AC voltage to the battery terminals. Asymmetric rectifiers have a positive component, and half-wave rectifiers are used as the main design elements. This scheme has better results compared to DC and AC rectifiers. It is its design that will be discussed further.
In order to assemble a high-quality battery charging device, you will need a rectifier and a current amplifier. The rectifier consists of the following elements:
Electrical circuit of an asymmetric rectifier
In order to assemble the circuit, you will need to use a fuse rated for a maximum current of 1 A. The transformer can be taken from an old TV, the power of which should not exceed 150 W, and the output voltage should be 21 V. As a resistor, you need to take a powerful element of the MLT- brand 2. The rectifier diode must be designed for a current of at least 5 A, so the best option is models like D305 or D243. The amplifier is based on a regulator based on two transistors of the KT825 and 818 series. During installation, the transistors are installed on radiators to improve cooling.
The assembly of such a circuit is carried out using a hinged method, that is, all the elements are located on the old board cleared of tracks and connected to each other using wires. Its advantage is the ability to adjust the output current for charging the battery. The disadvantage of the diagram is the need to find the necessary elements, as well as arrange them correctly.
The simplest analogue of the above diagram is a more simplified version, shown in the photo below.
Simplified circuit of a rectifier with a transformer
It is proposed to use a simplified circuit using a transformer and rectifier. In addition, you will need a 12 V and 40 W (car) light bulb. Assembling the circuit is not difficult even for a beginner, but it is important to pay attention to the fact that the rectifier diode and the light bulb must be located in the circuit that is fed to the negative terminal of the battery. The disadvantage of this scheme is that it produces a pulsating current. To smooth out pulsations, as well as reduce strong beats, it is recommended to use the circuit presented below.
A circuit with a diode bridge and a smoothing capacitor reduces ripple and reduces runout
Recently, a car charging option that you can make yourself using a computer power supply has become popular.
Initially you will need a working power supply. Even a unit with a power of 200 W is suitable for such purposes. It produces a voltage of 12 V. It will not be enough to charge the battery, so it is important to increase this value to 14.4 V. Step-by-step instructions for making a charger for a battery from a computer power supply are as follows:
The end of the green wire must be soldered to the negative contacts where the black wires were located
The TL494 microcontroller is responsible for the PWM operating mode
The resistor indicated by the purple dot must be desoldered
A regulator is soldered in place of the removed resistor
Output voltage is regulated by variable resistor
The resulting resistance should be 120.8 kOhm
Soldering resistors in series adds up their resistance
General view of the charger from the computer power supply
This is interesting! The assembled charger has the function of protection against short circuit current, as well as against overload, but it does not protect against polarity reversal, so you should solder the output wires of the appropriate color (red and black) so as not to mix them up.
When connecting the charger to the battery terminals, a current of about 5-6 A will be supplied, which is the optimal value for devices with a capacity of 55-60 A/h. The video below shows how to make a charger for a battery from a computer power supply with voltage and current regulators.
Let's consider a few more options for independent battery chargers.
One of the simplest and fastest ways to revive a dead battery. To implement the scheme for reviving the battery using charging from a laptop, you will need:
Let's move on to the implementation of the scheme. The light bulb is used to limit the current to an optimal value. You can use a resistor instead of a light bulb.
A laptop charger can also be used to “revive” a car battery.
Assembling such a scheme is not difficult. If you do not plan to use the laptop charger for its intended purpose, you can cut off the plug and then connect the clamps to the wires. First, use a multimeter to determine the polarity. The light bulb is connected to a circuit that goes to the positive terminal of the battery. The negative terminal from the battery is connected directly. Only after connecting the device to the battery can voltage be supplied to the power supply.
Using the transformer block, which is located inside the microwave, you can make a charger for the battery.
Step-by-step instructions for making a homemade charger from a transformer block from a microwave are presented below.
Connection diagram of a transformer block, diode bridge and capacitor to a car battery
The device can be assembled on any base. It is important that all structural elements are reliably protected. If necessary, the circuit can be supplemented with a switch, as well as a voltmeter.
If the search for a transformer has led to a dead end, then you can use the simplest circuit without step-down devices. Below is a diagram that allows you to implement a charger for a battery without using voltage transformers.
Electrical circuit of the charger without using a voltage transformer
The role of transformers is performed by capacitors, which are designed for a voltage of 250V. The circuit should include at least 4 capacitors, placing them in parallel. A resistor and an LED are connected in parallel to the capacitors. The role of the resistor is to dampen the residual voltage after disconnecting the device from the network.
The circuit also includes a diode bridge designed to operate with currents up to 6A. The bridge is included in the circuit after the capacitors, and the wires going to the battery for charging are connected to its terminals.
Separately, you should understand the question of how to properly charge the battery with a homemade charger. To do this, it is recommended to adhere to the following recommendations:
Based on the above recommendations, it should be concluded that homemade devices, although acceptable, are still not capable of replacing factory ones. Making your own charger is not safe, especially if you are not confident that you can do it correctly. The material presents the simplest schemes for implementing chargers for car batteries, which will always be useful in the household.
The steady trend in the development of portable electronics almost every day forces the average user to deal with charging the batteries of their mobile devices. Whether you are the owner of a mobile phone, tablet, laptop or even a car, one way or another you will repeatedly have to deal with charging the batteries of these devices. Today, the market for choosing chargers is so vast and large that in this variety it is quite difficult to make a competent and correct choice of a charger suitable for the type of battery used. In addition, today there are more than 20 types of batteries with different chemical compositions and bases. Each of them has its own specific charge and discharge operation. Due to economic benefits, modern production in this area is now concentrated primarily on the production of lead-acid (gel) (Pb), nickel-metal-hydride (NiMH), nickel-cadmium (NiCd) batteries and lithium-based batteries - lithium-ion ( Li-ion) and lithium-polymer (Li-polymer). The latter of these, by the way, are actively used in powering portable mobile devices. Mainly, lithium batteries have earned popularity due to the use of relatively inexpensive chemical components, a large number of recharge cycles (up to 1000), high specific energy, low degree of self-discharge, and the ability to hold capacity at negative temperatures.
The electrical circuit of the charger for lithium batteries used in mobile gadgets boils down to providing them with a constant voltage during charging, which exceeds the nominal voltage by 10–15%. For example, if a 3.7 V lithium-ion battery is used to power a mobile phone, then to charge it you need a stabilized power source of sufficient power to maintain the charge voltage no higher than 4.2 V - 5 V. That is why most portable chargers that come with the device are designed for a nominal voltage of 5V, determined by the maximum voltage of the processor and battery charge, taking into account the built-in stabilizer.
Of course, you shouldn’t forget about the charge controller, which takes care of the main algorithm for charging the battery, as well as polling its status. Modern lithium batteries produced for mobile devices with low current consumption already come with a built-in controller. The controller performs the function of limiting the charge current depending on the current capacity of the battery, turns off the voltage supply to the device in the event of a critical battery discharge, and protects the battery in the event of a load short circuit (lithium batteries are very sensitive to high load current and tend to get very hot and even explode). For the purpose of unification and interchangeability of lithium-ion batteries, back in 1997, Duracell and Intel developed a control bus for polling the status of the controller, its operation and charge, called SMBus. Drivers and protocols were written for this bus. Modern controllers still use the basics of the charging algorithm prescribed by this protocol. In terms of technical implementation, there are many microcircuits that can implement charge control of lithium batteries. Among them, the MCP738xx series, MAX1555 from MAXIM, STBC08 or STC4054 with a built-in protective n-channel MOSFET transistor, a charge current detection resistor and a controller supply voltage range from 4.25 to 6.5 Volts stand out. At the same time, in the latest microcircuits from STMicroelectronics, the battery charge voltage value of 4.2 V has a spread of only +/- 1%, and the charging current can reach 800 mA, which will allow charging batteries with a capacity of up to 5000 mAh.
Considering the charging algorithm for lithium-ion batteries, it is worth saying that this is one of the few types that provide the certified ability to charge with a current of up to 1C (100% of the battery capacity). Thus, a battery with a capacity of 3000 mAh can be charged with a current of up to 3A. However, frequent charging with a large “shock” current, although it will significantly reduce its time, will at the same time quite quickly reduce the battery capacity and render it unusable. From the experience of designing electrical circuits for chargers, we will say that the optimal charging value for a lithium-in (polymer) battery is 0.4C - 0.5C of its capacity.
A current value of 1C is allowed only at the moment of initial battery charging, when the battery capacity reaches approximately 70% of its maximum value. An example would be the charging of a smartphone or tablet, when the initial restoration of capacity occurs in a short time, and the remaining percentages accumulate slowly.
In practice, quite often the effect of deep discharge of a lithium battery occurs when its voltage drops below 5% of its capacity. In this case, the controller is not able to provide sufficient starting current to build up the initial charge capacity. (This is why it is not recommended to discharge such batteries below 10%). To solve such situations, you need to carefully disassemble the battery and turn off the built-in charge controller. Next, you need to connect an external charge source to the battery terminals, capable of delivering a current of at least 0.4C of the battery capacity and a voltage of no higher than 4.3V (for 3.7V batteries). The electrical circuit of the charger for the initial stage of charging such batteries can be used from the example below.
This circuit consists of a 1A current stabilizer. (set by resistor R5) on the parametric stabilizer LM317D2T and the switching voltage regulator LM2576S-adj. The stabilization voltage is determined by feedback to the 4th leg of the voltage stabilizer, that is, the ratio of resistances R6 and R7, which set the maximum battery charging voltage at idle. The transformer must produce 4.2 - 5.2 V alternating voltage on the secondary winding. Then, after stabilization, we will receive 4.2 - 5V DC voltage, sufficient to charge the above-mentioned battery.
Nickel - metal - hydride batteries (NiMH) can most often be found in standard battery housings - this is the form factor AAA (R03), AA (R6), D, C, 6F22 9V. The electrical circuit of the charger for NiMH and NiCd batteries must include the following functionality related to the specific charging algorithm of this type of battery.
Different batteries (even with the same parameters) change their chemical and capacitive characteristics over time. As a result, it becomes necessary to organize the charging algorithm for each instance individually, since during the charging process (especially with high currents, which nickel batteries allow), excessive overcharging affects the rapid overheating of the battery. Temperatures during charging above 50 degrees due to chemically irreversible decomposition processes of nickel will completely destroy the battery. Thus, the electrical circuit of the charger must have the function of monitoring the temperature of the battery. To increase the service life and the number of recharge cycles of a nickel battery, it is advisable to discharge each cell to a voltage of at least 0.9V. current of about 0.3C from its capacity. For example, a battery with 2500 – 2700 mAh. Discharge the active load with a current of 1A. Also, the charger must support “training” charging, when a cyclic discharge to 0.9V occurs over several hours, followed by charging with a current of 0.3 - 0.4C. Based on practice, up to 30% of dead nickel batteries can be revived in this way, and nickel-cadmium batteries can be “reanimated” much more readily. According to the charging time, electrical circuits of chargers can be divided into “accelerated” (charge current up to 0.7 C with a full charge time of 2 – 2.5 hours), “medium duration” (0.3 – 0.4 C – charge in 5 – 6 hours .) and “classic” (current 0.1C – charging time 12 – 15 hours). When designing a charger for a NiMH or NiCd battery, you can also use the generally accepted formula for calculating charging time in hours:
T = (E/I) ∙ 1.5
where E is the battery capacity, mA/h,
I – charge current, mA,
1.5 – coefficient for compensation of efficiency during charging.
For example, the charging time of a battery with a capacity of 1200 mAh. a current of 120 mA (0.1C) will be:
(1200/120)*1.5 = 15 hours.
From the experience of operating chargers for nickel batteries, it is worth noting that the lower the charging current, the more recharge cycles the element will endure. As a rule, the manufacturer indicates the passport cycles when charging the battery with a current of 0.1 C with the longest charge time. The charger can determine the degree of charge of the cans by measuring the internal resistance due to the difference in voltage drop at the time of charging and discharging with a certain current (∆U method).
So, taking into account all of the above, one of the simplest solutions for self-assembling the electrical circuit of the charger and at the same time highly efficient is Vitaly Sporysh’s circuit, a description of which can easily be found on the Internet.
The main advantages of this circuit are the ability to charge both one and two batteries connected in series, thermal control of the charge using a digital thermometer DS18B20, control and measurement of current during charging and discharging, automatic shutdown upon completion of charging, and the ability to charge the battery in an “accelerated” mode. In addition, with the help of specially written software and an additional board on the MAX232 TTL level converter chip, it is possible to control charging on a PC and further visualize it in the form of a graph. The disadvantages include the need for independent two-level power supply.
Lead-based (Pb) batteries can often be found in devices with high current consumption: cars, electric vehicles, uninterruptible power supplies, and as power sources for various power tools. There is no point in listing their advantages and disadvantages, which can be found on many sites on the Internet. In the process of implementing the electrical circuit of the charger for such batteries, two charging modes should be distinguished: buffer and cyclic.
Buffer charging mode involves simultaneously connecting both the charger and the load to the battery. This connection can be seen in uninterruptible power supplies, cars, wind and solar power systems. At the same time, during recharging, the device acts as a current limiter, and when the battery reaches its capacity, it switches to voltage limiting mode to compensate for self-discharge. In this mode, the battery acts as a supercapacitor. Cyclic mode involves turning off the charger when charging is complete and reconnecting it if the battery is low.
There are quite a lot of circuit solutions for charging these batteries on the Internet, so let’s look at some of them. For a novice radio amateur to implement a simple charger “on the knees,” the electrical circuit of the charger on the L200C chip from STMicroelectronics is perfect. The microcircuit is an ANALOG current regulator with the ability to stabilize voltage. Of all the advantages that this microcircuit has, it is the simplicity of the circuit design. Perhaps this is where all the advantages end. According to the datasheet for this chip, the maximum charge current can reach 2A, which theoretically will allow you to charge a battery with a capacity of up to 20 A/h with voltage 
(adjustable) from 8 to 18V. However, as it turned out in practice, this microcircuit has much more disadvantages than advantages. Already when charging a 12-amp lead-gel SLA battery with a current of 1.2A, the microcircuit requires a radiator with an area of at least 600 square meters. mm. A radiator with a fan from an old processor works well. According to the documentation for the microcircuit, voltages up to 40V can be applied to it. In fact, if you apply a voltage of more than 33V to the input. – the microcircuit burns out. This charger requires a fairly powerful power source capable of delivering a current of at least 2A. According to the above diagram, the secondary winding of the transformer should produce no more than 15 - 17V. alternating voltage. The output voltage value at which the charger determines that the battery has reached its capacity is determined by the Uref value on the 4th leg of the microcircuit and is set by the resistive divider R7 and R1. Resistors R2 – R6 create feedback, determining the limit value of the battery charging current. 
Resistor R2 at the same time determines its minimum value. When implementing a device, do not neglect the power value of the feedback resistances and it is better to use the ratings indicated in the circuit. To implement switching of the charging current, the best option would be to use a relay switch to which resistors R3 - R6 are connected. It is better to avoid using a low-resistance rheostat. This charger is capable of charging lead-based batteries with a capacity of up to 15 Ah. provided that the chip is well cooled.
The electrical circuit of a 3A pulse charger will help to significantly reduce the charging dimensions of small-capacity lead batteries (up to 20 A/h). current stabilizer with voltage regulation LM2576-ADJ.
For charging lead-acid or gel batteries with a capacity of up to 80A/h. (for example, automobiles). The impulse electrical circuit of a universal type charger presented below is perfect.
The circuit was successfully implemented by the author of this article in a case from an ATX computer power supply. Its elemental base is based on radioelements, mostly taken from a disassembled computer power supply. The charger works as a current stabilizer up to 8A. with adjustable charge cut-off voltage. Variable resistance R5 sets the value of the maximum charge current, and resistor R31 sets its limit voltage. A shunt on R33 is used as a current sensor. Relay K1 is necessary to protect the device from changing the polarity of the connection to the battery terminals. Pulse transformers T1 and T21 in finished form were also taken from a computer power supply. The electrical circuit of the charger works as follows:
1. turn on the charger with the battery disconnected (charging terminals folded back)
2. We set the charge voltage with variable resistance R31 (upper in the photo). For lead 12V. battery it should not exceed 13.8 - 14.0 V.
3. When the charging terminals are connected correctly, we hear the relay click, and on the lower indicator we see the value of the charging current, which we set with the lower variable resistance (R5 according to the diagram).
4. The charging algorithm is designed in such a way that the device charges the battery with a constant specified current. As the capacity accumulates, the charging current tends to a minimum value, and “recharging” occurs due to the previously set voltage.
A completely drained lead battery will not turn on the relay, nor will the charging itself. Therefore, it is important to provide a forced button for supplying instantaneous voltage from the internal power source of the charger to the control winding of relay K1. It should be remembered that when the button is pressed, the protection against polarity reversal will be disabled, so before a forced start, you need to pay special attention to the correct connection of the charger terminals to the battery. As an option, it is possible to start charging from a charged battery, and only then transfer the charging terminals to the required installed battery. The developer of the circuit can be found under the nickname Falconist on various radio-electronic forums.
To implement the voltage and current indicator, a circuit was used on the PIC16F690 pic controller and “super-available parts”, the firmware and operation description of which can be found on the Internet.
This electrical circuit of the charger, of course, does not claim to be a “reference”, but it is fully capable of replacing expensive industrial chargers, and can even significantly surpass many of them in functionality. In conclusion, it is worth saying that the latest universal charger circuit is designed mainly for a person trained in radio design. If you are just starting out, then it is better to use much simpler circuits in a powerful charger using an ordinary powerful transformer, a thyristor and its control system using several transistors. An example of the electrical circuit of such a charger is shown in the photo below.
See also diagrams.
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