Every motorist sooner or later has problems with the battery. I did not escape this fate. 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, having made an audit in the garage and having found a suitable transformer there, I decided to do the exercises myself.
In the same place, among the unnecessary junk, I also found a voltage regulator from an old TV, which, in my opinion, is wonderfully suitable as a case.
Having studied the vast expanses of the Internet and really assessing my strength, I chose probably the simplest scheme.
Having printed out the scheme, I went to a neighbor who is fond of radio electronics. Within 15 minutes, he typed the necessary details for me, cut off a piece of foil textolite and gave me a marker for drawing circuit boards. Having spent about an hour of time, I drew an acceptable board (the installation is spacious, the dimensions of the case allow). I won’t tell you how to poison the board, there is a lot of information about this. I took my creation to a neighbor, and he pickled 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 bought on the market, the main thing is that it is rated for a current of at least 10 amperes. I found diodes D 242, their characteristics are quite suitable, and on a piece of textolite I soldered a diode bridge.
The thyristor must be installed on a radiator, as it heats up noticeably during operation.
Separately, I must say about the ammeter. I had to buy it in a store, where the sales assistant 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’ll add on my own that the dissipation power of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but I had a 4-watt shunt warming up. I don’t know the reason, I don’t have enough experience in such cases, but, having decided that I basically need the readings of an ammeter, and not a voltmeter, I measured it. Moreover, in the voltmeter mode, the shunt noticeably heated up in 30-40 seconds. So, having collected everything I needed and checked everything on a stool, I took up the case. Having completely disassembled the stabilizer, I took out all its stuffing.
Having marked the front wall, I drilled holes for a variable resistor and a switch, then I drilled holes for an ammeter with a small-diameter drill around the circumference. The sharp edges were finished with a file.
Having scratched my head a little over the location of the transformer and the radiator with a thyristor, I settled on this option.
I bought a couple more crocodile clips and everything is ready to charge. A feature of this circuit is that it only works under load, therefore, having assembled 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 conclusions, 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.
Who has not encountered in their practice the need to charge the battery and, disappointed in the absence of a charger with the necessary parameters, was forced to purchase a new charger in the store, or assemble the necessary circuit again?
So I repeatedly had to solve the problem of charging various batteries when there was no suitable charger at hand. I had to hastily collect something simple, in relation to a specific battery.
The situation was bearable until the moment when there was a need for mass training and, accordingly, charging the batteries. It was necessary to make several universal chargers - inexpensive, operating in a wide range of input and output voltages and charging currents.
The charger circuits proposed below were developed for charging lithium-ion batteries, but it is possible to charge other types of batteries and composite batteries (using the same type of cells, hereinafter - AB).
All presented schemes have the following main parameters:
input voltage 15-24 V;
charge current (adjustable) up to 4 A;
output voltage (adjustable) 0.7 - 18 V (at Uin = 19V).
All circuits were designed to work with power supplies from laptops or to work with other power supplies with DC output voltages from 15 to 24 Volts and are built on widely used components that are present on the boards of old computer power supplies, power supplies of other devices, laptops, etc.
Memory diagram No. 1 (TL494)
The memory in scheme 1 is a powerful pulse generator operating in the range from tens to a couple of thousand hertz (the frequency was varied during research), with an adjustable pulse width.
The battery is charged by pulses of current, limited by the feedback formed by the current sensor R10, connected between the common wire of the circuit and the source of the key on the field-effect transistor VT2 (IRF3205), the R9C2 filter, pin 1, which is the “direct” input of one of the error amplifiers of the TL494 chip.
The inverse input (pin 2) of the same error amplifier is supplied with an adjustable by means of a variable resistor PR1, a comparison voltage from a reference voltage source built into the microcircuit (ION - pin 14), which changes the potential difference between the inputs of the error amplifier.
As soon as the voltage on R10 exceeds the voltage value (set by the variable resistor PR1) at pin 2 of the TL494 chip, the charging current pulse will be interrupted and resumed again only at the next cycle of the pulse sequence generated by the chip generator.
By adjusting the pulse width at the gate of the transistor VT2 in this way, we control the charging current of the battery.
Transistor VT1, connected in parallel with the gate of a powerful key, provides the necessary discharge rate of the gate capacitance of the latter, preventing "smooth" locking of VT2. In this case, the amplitude of the output voltage in the absence of AB (or other load) is almost equal to the input supply voltage.
With a resistive load, the output voltage will be determined by the current through the load (its resistance), which will allow using this circuit as a current driver.
When the battery is charging, the voltage at the output of the key (and, therefore, at the battery itself) over time will tend to grow towards the value determined by the input voltage (theoretically) and this, of course, cannot be allowed, knowing that the voltage value of the lithium battery being charged should be limited to 4.1 V (4.2 V). Therefore, a threshold device circuit is used in the memory, which is a Schmitt trigger (hereinafter - TSh) on the op-amp KR140UD608 (IC1) or on any other op-amp.
When the required voltage value on the battery is reached, at which the potentials at the direct and inverse inputs (pins 3, 2 - respectively) of IC1 are equal, a high logic level will appear at the output of the op-amp (almost equal to the input voltage), forcing the HL2 charging end indicator LED and the LED to light up. optocoupler VH1 which will open its own transistor, blocking the supply of pulses to the output U1. The key on VT2 will close, the battery charge will stop.
At the end of the battery charge, it will begin to discharge through the reverse diode built into VT2, which will turn out to be directly connected with respect to the battery and the discharge current will be approximately 15-25 mA, taking into account the discharge also through the elements of the TS circuit. If this circumstance seems critical to someone, a powerful diode should be placed in the gap between the drain and the negative terminal of the battery (preferably with a small forward voltage drop).
The TS hysteresis in this version of the charger is chosen so that the charge will start again when the voltage on the battery drops to 3.9 V.
This charger can also be used to charge serially connected lithium (and not only) batteries. It is enough to calibrate the required response threshold using a variable resistor PR3.
So, for example, a charger assembled according to scheme 1 functions with a three-section sequential battery from a laptop, consisting of dual elements, which was mounted instead of a nickel-cadmium battery for a screwdriver.
The power supply unit from the laptop (19V/4.7A) is connected to the charger assembled in the standard case of the screwdriver's charger instead of the original circuit. The charging current of the “new” battery is 2 A. At the same time, the VT2 transistor, working without a radiator, heats up to a temperature of 40-42 C at the maximum.
The charger is turned off, of course, when the voltage at the battery reaches 12.3V.
The TS hysteresis remains the same in PERCENTAGE when the response threshold is changed. That is, if at a shutdown voltage of 4.1 V, the charger was re-enabled when the voltage dropped to 3.9 V, then in this case, the charger is re-enabled when the battery voltage drops to 11.7 V. But if necessary, the hysteresis depth can change.
Charger Threshold and Hysteresis Calibration
Calibration occurs when using an external voltage regulator (laboratory PSU).The upper threshold for TS operation is set.
1. Disconnect the upper terminal PR3 from the memory circuit.
2. We connect the “minus” of the laboratory PSU (hereinafter LBP everywhere) to the negative terminal for the battery (the battery itself should not be in the circuit during setup), the “plus” of the LBP to the positive terminal for the battery.
3. Turn on the memory and LBP and set the required voltage (12.3 V, for example).
4. If the indication of the end of the charge is on, rotate the PR3 slider down (according to the scheme) until the indication (HL2) goes out.
5. Slowly rotate the PR3 engine up (according to the diagram) until the indication lights up.
6. Slowly reduce the voltage level at the LBP output and monitor the value at which the indication goes out again.
7. Check the level of operation of the upper threshold again. Good. You can adjust the hysteresis if you are not satisfied with the voltage level that turns on the memory.
8. If the hysteresis is too deep (the charger is switched on at a too low voltage level - below, for example, the level of the AB discharge, unscrew the PR4 slider to the left (according to the diagram) or vice versa, - if the hysteresis depth is insufficient, - to the right (according to the diagram). hysteresis depth, the threshold level can shift by a couple of tenths of a volt.
9. Make a test run by raising and lowering the voltage level at the output of the LBP.
Setting the current mode is even easier.
1. We turn off the threshold device by any available (but safe) methods: for example, by “planting” the PR3 engine on the common wire of the device or by “shorting” the LED of the optocoupler.
2. Instead of AB, we connect a load in the form of a 12-volt light bulb to the output of the charger (for example, I used a pair of 12V lamps for 20 W to set up).
3. We include an ammeter in the gap of any of the power wires at the input of the memory.
4. Set the PR1 slider to the minimum (maximum left according to the diagram).
5. Turn on the memory. Smoothly rotate the PR1 adjustment knob in the direction of increasing current until the required value is obtained.
You can try to change the load resistance in the direction of lower values of its resistance by connecting in parallel, say, another of the same lamp or even “short-circuit” the memory output. The current should not change significantly.
In the process of testing the device, it turned out that frequencies in the range of 100-700 Hz turned out to be optimal for this circuit, provided that IRF3205, IRF3710 (minimum heating) were used. Since TL494 is not fully used in this circuit, the free error amplifier of the chip can be used, for example, to work with a temperature sensor.
It should also be borne in mind that with an incorrect layout, even a correctly assembled pulse device will not work correctly. Therefore, one should not neglect the experience of assembling power pulse devices, which has been repeatedly described in the literature, namely: all “power” connections of the same name should be located at the shortest distance relative to each other (ideally, at one point). So, for example, connection points such as the VT1 collector, the terminals of the resistors R6, R10 (connection points with the common wire of the circuit), terminal 7 U1 - should be combined at almost one point or through a direct short and wide conductor (bus). The same applies to the drain VT2, the output of which should be "hung" directly on the "-" terminal of the battery. The IC1 pins must also be in close "electrical" proximity to the AB terminals.
Memory diagram No. 2 (TL494)
Scheme 2 does not differ much from scheme 1, but if the previous version of the charger was designed to work with an AB screwdriver, then the charger in scheme 2 was conceived as a universal, small-sized (without unnecessary setting elements), designed to work both with composite, series-connected elements up to 3, and with single ones.
As you can see, to quickly change the current mode and work with a different number of series-connected elements, fixed settings are introduced with trimmer resistors PR1-PR3 (current setting), PR5-PR7 (setting the charging end threshold for a different number of elements) and switches SA1 (current selection charging) and SA2 (selection of the number of battery cells to be charged).
The switches have two directions, where their second sections switch the mode selection indication LEDs.
Another difference from the previous device is the use of the second error amplifier TL494 as a threshold element (switched on according to the TS scheme), which determines the end of the battery charging.
Well, and, of course, a p-conductivity transistor was used as a key, which simplified the full use of the TL494 without the use of additional components.
The procedure for setting the thresholds for the end of charging and current modes is the same, as well as for setting the previous version of the memory. Of course, for a different number of elements, the response threshold will change multiples.
When testing this circuit, a stronger heating of the key on the VT2 transistor was noticed (when prototyping, I use transistors without a radiator). For this reason, you should use another transistor (which I simply didn’t have) of appropriate conductivity, but with better current parameters and lower open channel resistance, or double the number of transistors indicated in the circuit by connecting them in parallel with separate gate resistors.
The use of these transistors (in the "single" version) is not critical in most cases, but in this case, the placement of the device components is planned in a small-sized case using small-sized radiators or without radiators at all.
Memory diagram No. 3 (TL494)
In the charger in diagram 3, an automatic disconnection of the battery from the charger with switching to the load has been added. This is convenient for checking and researching unknown ABs. The TS hysteresis for working with the AB discharge should be increased to the lower threshold (for switching on the charger), equal to the full AB discharge (2.8-3.0 V).
Memory scheme No. 3a (TL494)
Scheme 3a - as a variant of scheme 3.
Memory diagram No. 4 (TL494)
The charger in scheme 4 is no more complicated than the previous devices, but the difference from the previous schemes is that the battery here is charged with direct current, and the charger itself is a stabilized current and voltage regulator and can be used as a laboratory power supply module, classically built according to the "datashit" canons.
Such a module is always useful for bench tests of both battery and other devices. It makes sense to use built-in instruments (voltmeter, ammeter). Formulas for calculating storage and interference chokes are described in the literature. Let me just say that I used ready-made various chokes (with the range of indicated inductances) during testing, experimenting with a PWM frequency from 20 to 90 kHz. I did not notice any particular difference in the operation of the regulator (in the range of output voltages of 2-18 V and currents of 0-4 A): slight changes in the heating of the key (without a radiator) suited me quite well. Efficiency, however, is higher when using smaller inductances.
The regulator worked best with two 22 µH chokes connected in series in square armored cores from converters integrated into laptop motherboards.
Memory Schematic #5 (MC34063)
In diagram 5, a variant of the SHI-controller with current and voltage regulation is made on the PWM / PWM MC34063 microcircuit with a “makeweight” on the CA3130 op-amp (other op-amps can be used), with the help of which the current is adjusted and stabilized.
This modification somewhat expanded the capabilities of the MC34063, in contrast to the classic inclusion of a microcircuit, allowing the smooth current adjustment function to be implemented.
Memory Diagram No. 6 (UC3843)
In diagram 6, a variant of the SHI controller is made on the UC3843 (U1) chip, the CA3130 (IC1) op-amp, and the LTV817 optocoupler. The current regulation in this version of the memory is carried out using a variable resistor PR1 at the input of the current amplifier of the microcircuit U1, the output voltage is regulated using PR2 at the inverting input of IC1.
At the "direct" input of the op-amp there is a "reverse" reference voltage. That is, the regulation is carried out with respect to the "+" supply.
In schemes 5 and 6, the same sets of components (including chokes) were used in the experiments. According to the test results, all of the listed circuits are not much inferior to each other in the declared range of parameters (frequency / current / voltage). Therefore, a circuit with fewer components is preferable for repetition.
Memory diagram No. 7 (TL494)
The memory in scheme 7 was conceived as a bench device with maximum functionality, therefore there were no restrictions in terms of the volume of the circuit and the number of adjustments. This version of the memory is also made on the basis of the SHI current and voltage regulator, as well as the option in diagram 4.
Additional modes have been added to the scheme.
1. "Calibration - charge" - for pre-setting the voltage thresholds for the end and repetition of charging from an additional analog regulator.
2. "Reset" - to reset the memory to charge mode.
3. "Current - buffer" - to transfer the regulator to current or buffer (limiting the output voltage of the regulator in the joint supply of the device with the voltage of the battery and the regulator) charge mode.
A relay was used to switch the battery from the "charge" mode to the "load" mode.
Working with the memory is similar to working with previous devices. Calibration is carried out by switching the toggle switch to the "calibration" mode. In this case, the contact of the toggle switch S1 connects the threshold device and the voltmeter to the output of the integral regulator IC2. Having set the necessary voltage for the forthcoming charging of a particular battery at the output of IC2, using PR3 (smoothly rotating) they achieve the ignition of the HL2 LED and, accordingly, the activation of relay K1. By reducing the voltage at the output of IC2, HL2 is quenched. In both cases, control is carried out by a built-in voltmeter. After setting the operation parameters of the PU, the toggle switch is switched to the charge mode.
Scheme No. 8
The use of a calibration voltage source can be avoided by using the charger itself for calibration. In this case, it is necessary to decouple the output of the TS from the SHI-regulator, preventing it from turning off when the battery charge ends, determined by the parameters of the TS. One way or another, the battery will be disconnected from the charger by the contacts of relay K1. The changes for this case are shown in Scheme 8.
In calibration mode, toggle switch S1 disconnects the relay from the plus of the power source to prevent inappropriate operation. At the same time, the indication of the operation of the TS works.
Toggle switch S2 performs (if necessary) forced activation of relay K1 (only when the calibration mode is disabled). Contact K1.2 is required to change the polarity of the ammeter when switching the battery to the load.
Thus, a unipolar ammeter will also monitor the load current. In the presence of a bipolar device, this contact can be excluded.
Charger design
In designs, it is desirable to use as variables and tuning resistors multi-turn potentiometers in order to avoid torment when setting the necessary parameters.
Design options are shown in the photo. Circuits were soldered on perforated breadboards impromptu. All the stuffing is mounted in cases from laptop PSUs.
They were used in the designs (they were also used as ammeters after a little refinement).
On the cases there are sockets for external connection of AB, loads, a jack for connecting an external power supply unit (from a laptop).
For 18 years of work in North-West Telecom, he has manufactured many different stands for testing various equipment being repaired.
He designed several, different in functionality and element base, digital pulse duration meters.
More than 30 rationalization proposals for the modernization of units of various specialized equipment, incl. - power supply. For a long time I have been more and more engaged in power automation and electronics.
Why am I here? Yes, because everyone here is the same as me. There are a lot of interesting things for me here, since I am not strong in audio technology, but I would like to have more experience in this particular direction.
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To participate in the voting, register and enter the site with your username and password.Very often, especially in the cold season, motorists are faced with the need to charge a car battery. It is possible, and desirable, to purchase a factory charger, preferably a charger-starter for use in the garage.
But, if you have the skills of electrical work, 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 a possible case when the battery is suddenly discharged away from home or a place of parking and service.
General information about the battery charging process
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 a long stop at low voltages, plate sulfation processes begin, which lead to a loss of battery capacity.
Therefore, during the wintering of the car in the parking lot or in the garage, it is necessary to constantly recharge the battery, monitor the voltage at its terminals. A better option is to remove the battery, bring it to a warm place, but still remember to maintain its charge.
The battery is charged with direct 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 charge current should be 6 amps. However, studies show that the lower the charge current, the less intense the processes of sulfation.
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 large currents of short duration. For example, such as when turning on the starter. Then comes 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.
Practically, desulphating pulse chargers are based on this principle. The battery in such devices is charged with a pulsed current. During the charging period (several milliseconds), a discharge short pulse of reverse polarity and a longer charging straight 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.
Schemes of homemade simple chargers for a car battery
Protozoa
Consider the case of how to charge the battery with improvised means. For example, a situation when you left your car near the house in the evening, forgetting to turn off some electrical equipment. By morning the battery was dead and the car would not start.
In this case, if your car starts up 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, limiting resistance.
What can be advised?
Now almost every home has a laptop. The power supply of a laptop or netbook, as a rule, has an output voltage of 19 volts, a current of at least 2 amperes. The outer pin of the power connector is minus, the inner pin is plus.
As a limiting resistance, and it is obligatory!!!, you can use the interior bulb of the car. You can, of course, more powerful from turn signals or even worse than stops or dimensions, but there is a possibility of overloading the power supply. The simplest circuit is being assembled: minus the power supply - a light bulb - minus the battery - plus the battery - plus the power supply. In a couple of hours, the battery will be recharged enough to be able to start the engine.
If a laptop is not available, you can pre-purchase a powerful rectifier diode with a reverse voltage of more than 1000 volts and a current of 3 amperes on the radio market. It has a small size, you can put it in the glove compartment for an emergency.
What to do in an emergency?
Ordinary 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 amperes. Not much, but during the night it will give 5 Amp-hours of capacity to the battery. Usually enough to turn the starter of the car a couple of times in the morning.
If you connect three lamps of 100 watts in parallel, the charge current will triple. You can almost half charge your car battery overnight. Sometimes, instead of lamps, an electric stove is turned on. But here the diode can already fail, and at the same time the battery.
In general, experiments of this kind with a direct charge of a battery from a 220-volt alternating voltage network extremely dangerous. They should only be used in extreme cases where there is no other way out.
From computer power supplies
Before you start making your own car battery charger, you should evaluate your knowledge and experience in the field of electrical and radio engineering. Accordingly, select the level of complexity of the device.
First of all, you should decide on the element base. Very often, computer users have old system units. There are power supplies. Along with the +5V supply voltage, they have 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 a diagram of a simple charger for a car battery from a computer power supply:
That's just the voltage of 12 volts is not enough. It is necessary to "disperse" it to 15. How? Usually by the "poke" method. They 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 gain of the feedback circuit is changed, respectively, and the output voltage.
It is difficult to explain in words, but usually users get it. 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 there is no power supply at hand, you can look for a transformer with a secondary winding of 12 - 18 volts. They were used in old tube TVs and other household appliances.
Now such transformers can be found in used uninterruptible power supplies, it can be bought for a penny in the secondary market. Next, proceed to the manufacture of a transformer charger.
Transformer chargers
Transformer chargers are the most common and safe devices widely used in motorist practice.
Video - a simple car battery charger using a transformer:
The simplest transformer charger circuit for a car battery contains:
- network transformer;
- rectifier bridge;
- restrictive load.
A large current flows through the limiting load, it is very hot, therefore, capacitors in the primary circuit of the transformer are often used to limit the charging current.
In principle, in such a circuit, you can do without a transformer, if you choose the right capacitor. But without galvanic isolation from the AC network, such a circuit will be dangerous in terms of electric shock.
More practical charger circuits for car batteries with regulation and limitation of the charge current. One of these schemes is shown in the figure:
As powerful rectifier diodes, you can use the rectifier bridge of a faulty car generator by slightly switching the circuit.
More sophisticated desulfation pulse chargers are usually made using microchips, even microprocessors. They are difficult to manufacture, require special installation and configuration skills. In this case, it is easier to purchase a factory device.
Safety requirements
Conditions to be met when using a homemade car battery charger:
- the charger and battery during charging must be located on a fireproof surface;
- in the case of using the simplest chargers, it is necessary to use personal protective equipment (insulating gloves, rubber mat);
- during the use of newly manufactured devices, constant monitoring of the charging process is necessary;
- the main controlled parameters of the charging process - current, voltage at the battery terminals, temperature of the charger and battery case, control of the moment of boiling;
- when charging at night, it is necessary to have residual current devices (RCD) in the network connection.
Video - a 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, of course, curious and informative. I, as a former radio engineer of the Soviet school, read with great interest. But in reality, now even “desperate” radio amateurs are unlikely to bother with finding circuits for a home-made charger and later assemble it with a soldering iron and radio components. Only fanatic radio amateurs will do this. It is much easier to buy a factory device, especially since the prices, I think, are affordable. As a last resort, you can turn to other motorists with a request to “light it up”, fortunately, now there are a lot of cars everywhere. What is written here is useful not so much for its practical value (although this is also), 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 pronounce it the first time. And it's very sad...
Michael
When the battery was old and half-dead, I often used a laptop power supply for recharging. 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 eagerly eats the charge, then the charge voltage increases, and when it reaches 15 V, I stop charging. It takes half an hour to an hour to confidently start the engine.
Ignat
I have a Soviet charger in my garage, called "Volna", 79th year of manufacture. Inside is a hefty and heavy transformer and several diodes, resistors and transistors. Almost 40 years in the ranks, and this despite the fact that we use it with our father and brother all the time and not only for charging, but also as a 12 V power supply. And now it’s really easier to buy a cheap Chinese device for five acres than to bother with soldering iron. And on Aliexpress you can even buy for a hundred and fifty, it will take a long time to send. Although I liked the option from the computer power supply, I have just a dozen of old ones lying around in the garage, but quite working ones.
San Sanych
Hmm. Of course, the pepsicol generation is growing ... :-\ The correct charger should give out 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 pull it out or, conversely, not install it back into the car. With a smaller potential difference, the battery will not be charged. 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 lots of these for sale. It is better to install diodes domestic, - D246A (it is necessary to put on a radiator with mica insulators). At worst - KD213A (these can be glued with superglue to an aluminum radiator). Any electrolytic capacitor with a capacity of at least 1000 microfarads 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 get the optimal charge for the battery. So we get 10 * root of 2 = 14.2 volts. I myself have such a charger since the time of the 412th Muscovite. Not killed at all. 🙂
Kirill
In principle, if you have the necessary transformer, it is not so difficult to assemble the transformer charger circuit yourself. Even for me, not a very big specialist in the field of radio electronics. Many say, they say, why fool around, if it's easier to buy. I agree, but this is not a matter of the final result, but of the process itself, because it is much more pleasant to use a thing made by one's own hands than a purchased one. And most importantly, if this home-made product comes out of a standing position, then the one who assembled it knows his battery charging thoroughly and is able to fix it quickly. And if a purchased product burns out, then you still need to dig and it’s not at all a fact that a breakdown will be found. I vote for devices of my own assembly!
Oleg
In general, I think that the ideal option is an industrial-made charger, so I have this and carry it in the trunk all the time. But life situations are different. Somehow I was visiting my daughter in Montenegro, but there they don’t carry anything with them at all, and even rarely anyone has it. So she forgot to close the door at night. The battery is discharged. No diode at hand, no computer. I found a Boshevsky screwdriver for 18 volts and 1 ampere of current from her. Here is his charge and used. True, I charged all night and periodically touched for overheating. But nothing withstood, in the morning they started with a half kick. So there are many options to look for. Well, as for home-made chargers, as a radio engineer I can only advise transformer ones, i.e. decoupled over the network, they are safe compared to capacitor, diode 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, no matter what the rated voltage exceeds the allowable one. It is necessary to take into account temperature differences and this is a very important point, especially in winter. When you decrease by a degree, increase it and vice versa. There is an approximate table depending on the type of battery - it is not difficult to remember it. Another important point is that all voltage and density measurements are made only on a cold, idle engine.
Vitalik
In general, I rarely use a charger, maybe once every two or three years, and then when I leave 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 almost daily in operation, the battery is charging and there is no need for such devices. Therefore, I think that buying for money what you practically do not use is not too smart. The best option is to assemble such a simple craft, for example, from a computer power supply, and let it lie around in anticipation of its hour. After all, it is fundamental here 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.
Nicholas
Just yesterday I recharged the battery from a charger for a screwdriver. The car was on the street, frost -28, the battery spun a couple of times and got up. They took out a screwdriver, a couple of wires, connected it and after half an hour the car started up safely.
Dmitry
A ready-made store charger is, of course, an ideal option, but who wants to put their hands on it, and considering that you don’t have to use it often, you can not spend money on a purchase and do the exercises yourself.
A home-made charger should be autonomous, not require supervision, 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 are above the norm. It must also provide reverse polarity protection.
The main mistakes that “kulibins” make are connecting directly to a household power supply, this is not even a mistake, but a violation of safety regulations, the next limitation of the charge current by capacities, and even more expensive: one battery of capacitors 32 microfarads per 350-400 V (less can not be) 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 transformer on iron, and you don’t need to make a separate protection, everything is ready.
If there is no computer power supply, you need to look for a transformer. Suitable power with filament windings from old tube TVs - TS-130, TS-180, TS-220, TS-270. They have plenty of power behind their eyes. You can find an old TN incandescent transformer in the car market.
But all this is only for those who are friends with the electrician. If not, don’t bother - you won’t make a charge that meets all the requirements, so buy ready-made and don’t waste time.
Laura
I got a charger from my grandfather. From Soviet times. Homemade. I don’t understand this at all, but my acquaintances, seeing him admiringly and respectfully, click their tongues, they say, this thing is “for centuries”. They say that it was assembled on some lamps and is still working. I don't actually use it, but that's beside the point. All Soviet equipment is scolded, but it turns out to be many times more reliable than modern, even home-made.
Vladislav
In general, a useful thing in the household, especially if there is a function for adjusting the output voltage
Alexei
I didn’t manage to use or assemble home-made chargers, but I can fully imagine the principle of assembly and operation. I think that homemade products are no worse than factory ones, just no one wants to mess around, especially since store prices are quite affordable.
Victor
In general, the schemes are simple, there are few details and they are affordable. Adjustment with some experience is also possible to do. So it is quite possible to collect. Of course, it is very pleasant to use the device, assembled with your own hands)).
Ivan
The charger, of course, is a useful thing, but now there are more interesting specimens on the market - their name is start-up chargers
Sergey
There are a lot of charger circuits and as a radio engineer I have tried many of them. Until last year, the scheme worked for me from Soviet times and it worked perfectly. But once in my garage (through my fault) the battery completely died and it took a cyclic mode to restore it. Then I didn’t bother (due to lack of time) with the creation of a new scheme, but simply went and bought it. And now I carry a charger in the trunk just in case.
Compliance with the operating mode of batteries, and in particular the charging mode, guarantees their trouble-free operation throughout the entire service life. The batteries are charged with a current, the value of which can be determined by the formula
where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.
A classic car battery charger consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats are used as current regulators (see Fig. 1) and transistor current stabilizers.
In both cases, significant thermal power is released on these elements, which reduces the efficiency of the charger and increases the likelihood of its failure.
To adjust the charging current, you can use a store of capacitors that are connected in series with the primary (mains) winding of the transformer and act as reactances that dampen excess mains voltage. A simplified version of such a device is shown in Fig. 2.
In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is negligible.
The disadvantage in Fig. 2 is the need to ensure the voltage on the secondary winding of the transformer is one and a half times greater than the rated load voltage (~ 18÷20V).
The charger circuit that provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.
It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.
With switches Q1 - Q4, you can connect various combinations of capacitors and thereby regulate the charging current.
The variable resistor R4 sets the response threshold K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.
On Fig. 4 shows another charger, in which the charging current is continuously adjustable from zero to the maximum value.
The change in the current in the load is achieved by adjusting the opening angle of the trinistor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5 slider. The maximum battery charge current is 10A, set by an ammeter. The device is provided on the mains and load side by fuses F1 and F2.
A variant of the printed circuit board of the charger (see Fig. 4), 60x75 mm in size, is shown in the following figure:
In the diagram in fig. 4 the secondary winding of the transformer must be designed for a current three times the charging current, and accordingly the power of the transformer must also be three times the power consumed by the battery.
This circumstance is a significant drawback of chargers with a current regulator trinistor (thyristor).
Note:
Rectifier bridge diodes VD1-VD4 and thyristor VS1 must be installed on radiators.
It is possible to significantly reduce power losses in the trinistor, and therefore increase the efficiency of the charger, by transferring the control element from the secondary winding circuit of the transformer to the primary winding circuit. such a device is shown in Fig. 5.
In the diagram in Fig. 5, the control unit is similar to that used in the previous version of the device. The trinistor VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is about 10 times less than the charge current, a relatively small thermal power is released on the VD1-VD4 diodes and the VS1 trinistor and they do not require installation on radiators. In addition, the use of a trinistor in the primary circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the shape factor of the current curve (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing the design (for example, use a variable resistor with a plastic axis).
A variant of the printed circuit board of the charger in Figure 5, 60x75 mm in size, is shown in the figure below:
Note:
Rectifier bridge diodes VD5-VD8 must be installed on radiators.
In the charger in Figure 5, the diode bridge VD1-VD4 of the type KTs402 or KTs405 with the letters A, B, C. The zener diode VD3 of the type KS518, KS522, KS524, or composed of two identical zener diodes with a total stabilization voltage of 16 ÷ 24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is single-junction, type KT117A, B, C, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247 and others). Diodes are installed on radiators with an area of at least 200 sq.cm, and the radiators will get very hot, you can install a fan for blowing into the charger case.
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