Every motorist sooner or later has problems with the battery. I did not escape this fate either. After 10 minutes of unsuccessful attempts to start my car, I decided that I needed to purchase or make my own charger. In the evening, after checking out the garage and finding a suitable transformer there, I decided to do the charging myself.
There, among the unnecessary junk, I also found a voltage stabilizer from an old TV, which, in my opinion, would work wonderfully as a housing.
Having scoured the vast expanses of the Internet and really assessed my strengths, I probably chose the simplest scheme.
After printing out the diagram, I went to a neighbor who is interested in radio electronics. Within 15 minutes, he collected the necessary parts for me, cut off a piece of foil PCB and gave me a marker for drawing circuit boards. Having spent about an hour, I drew an acceptable board (the dimensions of the case allow for spacious installation). I won’t tell you how to etch the board, there is a lot of information about this. I took my creation to my neighbor, and he etched it for me. In principle, you could buy a circuit board and do everything on it, but as they say to a gift horse...
Having drilled all the necessary holes and displayed the pinout of the transistors on the monitor screen, I took up the soldering iron and after about an hour I had a finished board.
A diode bridge can be bought on the market, the main thing is that it is designed for a current of at least 10 amperes. I found D 242 diodes, their characteristics are quite suitable, and I soldered a diode bridge on a piece of PCB.
The thyristor must be installed on a radiator, since it gets noticeably hot during operation.
Separately, I must say about the ammeter. I had to buy it in a store, where the sales consultant also picked up the shunt. I decided to modify the circuit a little and add a switch so that I could measure the voltage on the battery. Here, too, a shunt was needed, but when measuring voltage, it is connected not in parallel, but in series. The calculation formula can be found on the Internet; I would add that the dissipation power of the shunt resistors is of great importance. According to my calculations, it should have been 2.25 watts, but my 4-watt shunt was heating up. The reason is unknown to me, I don’t have enough experience in such matters, but having decided that I mainly needed the readings of an ammeter, and not a voltmeter, I decided on it. Moreover, in voltmeter mode the shunt noticeably warmed up within 30-40 seconds. So, having collected everything I needed and checked everything on the stool, I took up the body. Having completely disassembled the stabilizer, I took out all its contents.
Having marked the front wall, I drilled holes for the variable resistor and switch, then with a small diameter drill around the circumference I drilled holes for the ammeter. Sharp edges were finished with a file.
After racking my brains a bit over the location of the transformer and radiator with thyristor, I settled on this option.
I bought a couple more crocodile clips and everything is ready to charge. The peculiarity of this circuit is that it only works under load, so after assembling the device and not finding voltage at the terminals with a voltmeter, do not rush to scold me. Just hang at least a car light bulb on the terminals, and you will be happy.
Take a transformer with a voltage on the secondary winding of 20-24 volts. Zener diode D 814. All other elements are indicated in the diagram.
Homemade battery chargers usually have a very simple design, and in addition, increased reliability precisely due to the simplicity of the circuit. Another advantage of making a charger yourself is the relative cheapness of the components and, as a result, the low cost of the device.
The main task of such equipment is to maintain the charge of the car battery at the required level if necessary. If the battery discharge occurs near the house where there is the necessary device, then there will be no problems. Otherwise, when there is no suitable equipment to power the battery, and the funds are also insufficient, you can assemble the device yourself.
The need to use auxiliary means to recharge a car battery is primarily due to low temperatures in the cold season, when a half-discharged battery is a major and sometimes completely unsolvable problem unless the battery is recharged in time. Then homemade chargers for powering car batteries will become a salvation for users who do not plan to invest in such equipment, at least at the moment.
Up to a certain level, a car battery can receive power from the vehicle itself, or more precisely, from an electric generator. After this node, a relay is usually installed, responsible for setting the voltage to no more than 14.1V. In order for the battery to be charged to its maximum, a higher value of this parameter is required - 14.4V. Accordingly, batteries are used to implement such a task.
The main components of this device are a transformer and a rectifier. As a result, a direct current with a voltage of a certain value (14.4V) is supplied to the output. But why is there a run-up with the voltage of the battery itself - 12V? This is done in order to ensure the ability to charge a battery that has been discharged to a level where the value of this battery parameter was equal to 12V. If charging is characterized by the same parameter value, then powering the battery will become a difficult task.
Watch the video, the simplest device for charging a battery:
But there is a nuance here: a slight excess of the battery voltage level is not critical, while a significantly increased value of this parameter will have a very bad effect on the performance of the battery in the future. The operating principle that distinguishes any, even the simplest car battery charger, is to increase the resistance level, which will lead to a decrease in the charging current.
Accordingly, the higher the voltage value (tends to 12V), the lower the current. For normal operation of the battery, it is advisable to set a certain amount of charge current (about 10% of the capacity). In a hurry, it is tempting to change the value of this parameter to a higher value, however, this is fraught with negative consequences for the battery itself.
The main elements of a simple design: a diode and a heater. If you connect them correctly (in series) to the battery, you can achieve what you want - the battery will be charged in 10 hours. But for those who like to save electricity, this solution may not be suitable, because the consumption in this case will be about 10 kW. The operation of the resulting device is characterized by low efficiency.
Basic elements of a simple design
But to create a suitable modification, you will have to slightly modify individual elements, in particular, the transformer, the power of which should be at the level of 200-300 W. If you have old equipment, this part from a regular tube TV will do. To organize a ventilation system, a cooler will be useful; it is best if it comes from a computer.
When creating a simple charger for powering a battery with your own hands, the main elements are also a transistor and a resistor. To make the structure work, you will need a compact externally, but quite capacious metal case; a good option is a stabilizer box.
In theory, even a novice radio amateur who has not previously encountered complex circuits can assemble this kind of equipment.
Circuit diagram of a simple battery charger
The main difficulty lies in the need to modify the transformer. At this level of power, the windings are characterized by low voltage levels (6-7V), the current will be equal to 10A. Typically, a voltage of 12V or 24V is required, depending on the type of battery. To obtain such values at the output of the device, it is necessary to provide a parallel connection of the windings.
A homemade charger for powering a car battery begins with preparing the core. Winding the wire onto the windings is done with maximum compaction; it is important that the turns fit tightly to each other and there are no gaps left. We must not forget about the insulation, which is installed at intervals of 100 turns. The wire cross-section of the primary winding is 0.5 mm, the secondary winding is from 1.5 to 3.0 mm. If we consider that at a frequency of 50 Hz, 4-5 turns can provide a voltage of 1V, respectively, to obtain 18V, about 90 turns are required.
Next, a diode of suitable power is selected to withstand the loads applied to it in the future. The best option is a car generator diode. To eliminate the risk of overheating, it is necessary to ensure effective air circulation inside the housing of such a device. If the box is not perforated, you should take care of this before starting assembly. The cooler must be connected to the charger output. Its main task is to cool the diode and winding of the transformer, which is taken into account when choosing an area for installation.
Watch the video for detailed manufacturing instructions:
The circuit of a simple charger for powering a car battery also contains a variable resistor. For normal charging operation, it is necessary to obtain a resistance of 150 Ohms and a power of 5 W. The KU202N resistor model meets these requirements more than others. You can choose a different option from this, but its parameters should be similar in value to those indicated. The resistor's job is to regulate the voltage at the device's output. The KT819 transistor model is also the best option from a number of analogues.
As you can see, if you need to assemble a homemade charger for a car battery, its circuit is more than simple to implement. The only difficulty is the arrangement of all the elements and their installation in the housing with subsequent connection. But such work can hardly be called labor-intensive, and the cost of all the parts used is extremely low.
Some of the parts, and perhaps all of them, will probably be found at home by a radio amateur, for example, a cooler from an old computer, a transformer from a tube TV, an old housing from a stabilizer. As for the degree of efficiency, such devices, assembled with your own hands, do not have very high efficiency, however, as a result, they still cope with their task.
Watch the video, useful expert advice:
Thus, large investments in creating a homemade charger are not required. On the contrary, all the elements cost extremely little, which makes this solution stand out compared to a device that can be purchased ready-made. The scheme discussed above is not highly efficient, but its main advantage is a charged car battery, albeit after 10 hours. You can improve this option or consider many others proposed for implementation.
Today we have a very useful homemade product for car enthusiasts, especially in winter! This time we will tell you how to make a homemade charger from an old printer with your own hands!
If you have an old printer, don’t rush to throw it away; it has a power supply from which you can make a simple automatic charger for a car battery with the function of adjusting the voltage and charge current. At one time, I had a safety margin greater than that of printer print heads. In this regard, I have accumulated a couple of printers with absolutely working power supplies, quite suitable for creating low-power automatic battery chargers.
The device also uses another Lm7812 stabilizer chip, which powers a 12 Volt cooler (which was originally in this case).
The charger is assembled in the case, all the contents of the unit, except the cooler, are removed. Stabilizer chips Lm317 and Lm 7812 are each installed on its own radiator, which are screwed to a plastic case (ATTENTION they cannot be installed on a common radiator!).
The circuit is assembled by mounted mounting on stabilizer microcircuits. Resistors R2 and R3 with a power of 2-5 Watts in ceramic cases are responsible for limiting the charge current. They are installed so that it passes through them. Their value is calculated using the formula R=1.25(V)/I(A), you can calculate the maximum charge current you need. Since we are talking about calculations, let me remind you that we have If you need to smoothly regulate the charge current, you can install a powerful rheostat with an additional limiting resistor (so as not to exceed the maximum permissible current for Lm317)
In my case it was 24 Volts with a maximum load current of 1 Ampere. It is necessary to reserve 0.1 Ampere from this 1 Ampere for powering the cooler (the consumption current is indicated on the sticker) + I left 10% for a safety margin, respectively, for the main purpose - 0.8 Ampere remains for the charging current.
It is clear that you cannot quickly charge a car battery with a current of 800 mA. In one day, the battery can be supplied with 24 hours * 0.8 A = 19.2 Ampere hours, which is 30-45% of the capacity of a car battery (usually 45-65 Ah).
If you have a “donor” power supply with a current of 1.5 Amperes, you will be able to provide 30 Ampere hours per day, which is probably enough for a battery that has been in use for more than one year.
But, on the other hand, charging with a low current is more useful for the battery, “it is better absorbed”, just unscrew the plugs from the battery (if it is serviceable), connect the charger to the battery and that’s it! You can go about your business and not worry that the battery will be overcharged, the maximum voltage on the battery will not exceed 14.5 Volts, and the low charging current will prevent excessive overheating and boiling off of the electrolyte. Due to the fact that you don’t have to control the charging process, I think this can be safely called an automatic charger for car batteries, although there is no “tracking automation” in the circuit.
For convenience, the charger can be equipped with a Volt meter, which will make it possible to visually monitor the battery charging process. For example, like this for a couple of dollars.
The charger must be equipped with protection against polarity reversal. The role of such protection is performed by two diodes with a permissible current of 5 Amps connected to the output of the charger in combination with a 2 Ampere fuse (during installation, be careful and observe the polarity of diode connections!!!). If the charger is connected incorrectly to the battery, the battery current will flow into the charger through the fuse and “hit” the diode, when the current reaches 2 Amps, the fuse will save the world! Also, do not forget to provide the device with fuses for the 220 Volt circuit (in my case, for the 220 Volt circuit, the fuse is already inside the power supply).
We connect the charger to the car battery using special “crocodile” clips; when buying them on the Internet, pay attention to the physical size indicated in the characteristics, since you can easily buy crocodiles for a “laboratory power supply” that will be good for everyone, but will not fit on the positive one battery terminal, and reliable contact, as you yourself understand, is a must in such matters. For convenience, there are several nylon Velcro ties on the wires and the body with which you can carefully and compactly wind the wires.
I hope this printer recycling idea is useful to someone. If you have made homemade automatic chargers for car batteries (or non-automatic ones), please share with the readers of our site - send us a photo, diagram and a short description of your device by email. If you have questions about the scheme and operating principle, ask in the comments and I will answer.
The article will tell you how to make a homemade one with your own hands. You can use absolutely any circuits, but the simplest manufacturing option is to remake a computer power supply. If you have such a block, it will be quite easy to find a use for it. To power motherboards, voltages of 5, 3.3, 12 Volts are used. As you understand, the voltage of interest to you is 12 Volts. The charger will allow you to charge batteries whose capacity ranges from 55 to 65 Ampere-hours. In other words, it is enough to recharge the batteries of most cars.
To make the alteration, you need to use the diagram presented in the article. made with your own hands from the power supply of a personal computer, allows you to control the charging current and voltage at the output. It is necessary to pay attention to the fact that there is protection against short circuit - a 10 Ampere fuse. But it is not necessary to install it, since most power supplies of personal computers have protection that turns off the device in the event of a short circuit. Therefore, charger circuits for batteries from computer power supplies are able to protect themselves from short circuits.
The PSI controller (designated DA1), as a rule, is used in the power supply of two types - KA7500 or TL494. Now a little theory. Can a computer's power supply properly charge the battery? The answer is yes, since lead batteries in most cars have a capacity of 55-65 Ampere-hour. And for normal charging it needs a current equal to 10% of the battery capacity - no more than 6.5 Amperes. If the power supply has a power of over 150 W, then its “+12 V” circuit is capable of delivering such current.
To replicate a simple homemade battery charger, you need to slightly improve the power supply:
It turns out to be quite simple and homemade. You can use any circuits, but it’s easier to make it from a computer power supply - it’s lighter, easier to use, and more affordable. When compared with transformer devices, the mass of the devices differs significantly (as do the dimensions).
The back wall will now be the front; it is advisable to make it from a piece of material (textolite is ideal). On this wall it is necessary to install a charging current regulator, indicated in the diagram R10. It is best to use a current-sensing resistor as powerful as possible - take two with a power of 5 W and a resistance of 0.2 Ohm. But it all depends on the choice of battery charger circuit. Some designs do not require the use of high-power resistors.
When connecting them in parallel, the power is doubled, and the resistance becomes equal to 0.1 Ohm. On the front wall there are also indicators - a voltmeter and an ammeter, which allow you to monitor the relevant parameters of the charger. To fine-tune the charger, a trimming resistor is used, with which voltage is supplied to the 1st pin of the PHI controller.
Multi-core thin wires must be soldered to pins 1, 14, 15 and 16. Their insulation must be reliable so that heating does not occur under load, otherwise the homemade car charger will fail. After assembly, you need to set the voltage to about 14 Volts (+/-0.2 V) using a trimmer resistor. This is the voltage that is considered normal for charging batteries. Moreover, this value should be in idle mode (without a connected load).
You must install two alligator clips on the wires that connect to the battery. One is red, the other is black. These can be purchased at any hardware or auto parts store. This is how you get a simple homemade charger for a car battery. Connection diagrams: black is attached to the minus, and red to the plus. The charging process is completely automatic, no human intervention is required. But it is worth considering the main stages of this process.
During the initial cycle, the voltmeter will show a voltage of approximately 12.4-12.5 V. If the battery has a capacity of 55 Ah, then you need to rotate the regulator until the ammeter shows a value of 5.5 Amperes. This means that the charging current is 5.5 A. As the battery charges, the current decreases and the voltage tends to a maximum. As a result, at the very end the current will be 0 and the voltage will be 14 V.
Regardless of the selection of circuits and designs of chargers used for manufacturing, the operating principle is largely similar. When the battery is fully charged, the device begins to compensate for the self-discharge current. Therefore, you do not risk the battery overcharging. Therefore, the charger can be connected to the battery for a day, a week, or even a month.
If you don’t have measuring instruments that you wouldn’t mind installing in the device, you can refuse them. But for this it is necessary to make a scale for the potentiometer - to indicate the position for the charging current values of 5.5 A and 6.5 A. Of course, the installed ammeter is much more convenient - you can visually observe the process of charging the battery. But a battery charger, made with your own hands without the use of equipment, can be easily used.
The automatic charger is designed for charging and desulfating 12-volt batteries with a capacity of 5 to 100 Ah and assessing their charge level. The charger has protection against polarity reversal and short circuit of the terminals. It uses microcontroller control, thanks to which safe and optimal charging algorithms are implemented: IUoU or IUIoU, followed by recharging to a full charge level. Charging parameters can be adjusted for a specific battery manually or you can select those already included in the control program.Basic operating modes of the device for the presets included in the program.
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Charging mode - “Charge” menu. For batteries with capacities from 7Ah to 12Ah, the IUoU algorithm is set by default. This means:
- First step- charging with a stable current of 0.1C until the voltage reaches 14.6V
- second phase-charging with a stable voltage of 14.6V until the current drops to 0.02C
- third stage- maintaining a stable voltage of 13.8V until the current drops to 0.01C. Here C is the battery capacity in Ah.
- fourth stage- recharging. At this stage, the voltage on the battery is monitored. If it drops below 12.7V, the charge starts from the very beginning.
For starter batteries we use the IUIoU algorithm. Instead of the third stage, the current is stabilized at 0.02C until the battery voltage reaches 16V or after about 2 hours. At the end of this stage, charging stops and recharging begins.
>> Desulfation mode - “Training” menu. Here the training cycle is carried out: 10 seconds - discharge with a current of 0.01C, 5 seconds - charge with a current of 0.1C. The charge-discharge cycle continues until the battery voltage rises to 14.6V. Next is the usual charge.
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The battery test mode allows you to evaluate the degree of battery discharge. The battery is loaded with a current of 0.01C for 15 seconds, then the voltage measurement mode on the battery is turned on.
>> Control-training cycle. If you first connect an additional load and turn on the “Charge” or “Training” mode, then in this case, the battery will first be discharged to a voltage of 10.8 V, and then the corresponding selected mode will be turned on. In this case, the current and discharge time are measured, thus calculating the approximate capacity of the battery. These parameters are displayed on the display after charging is complete (when the message “Battery is charged” appears) when you press the “select” button. As an additional load, you can use a car incandescent lamp. Its power is selected based on the required discharge current. Usually it is set equal to 0.1C - 0.05C (10 or 20 hour discharge current).
Schematic diagram of an automatic car charger
Drawing of an automatic car charger board
The basis of the circuit is the AtMega16 microcontroller. Navigation through the menu is carried out using the buttons " left», « right», « choice" The “reset” button exits any operating mode of the charger to the main menu. The main parameters of charging algorithms can be configured for a specific battery; for this purpose, there are two customizable profiles in the menu. The configured parameters are saved in non-volatile memory.
To get to the settings menu, you need to select any of the profiles and press the “ choice", choose " installations», « profile parameters", profile P1 or P2. Having selected the desired option, click “ choice" Arrows " left" or " right» will change to arrows « up" or " down", which means the parameter is ready to change. Select the desired value using the “left” or “right” buttons, confirm with the “ choice" The display will show “Saved”, indicating that the value has been written to the EEPROM. Read more about the setup on the forum.
The control of the main processes is entrusted to the microcontroller. A control program is written into its memory, which contains all the algorithms. The power supply is controlled using PWM from the PD7 pin of the MK and a simple DAC based on elements R4, C9, R7, C11. The measurement of battery voltage and charging current is carried out using the microcontroller itself - a built-in ADC and a controlled differential amplifier. The battery voltage is supplied to the ADC input from the divider R10 R11.
Charging and discharging current are measured as follows. The voltage drop from the measuring resistor R8 through dividers R5 R6 R10 R11 is supplied to the amplifier stage, which is located inside the MK and connected to pins PA2, PA3. Its gain is set programmatically, depending on the measured current. For currents less than 1A, the gain factor (GC) is set equal to 200, for currents above 1A GC=10. All information is displayed on the LCD connected to ports PB1-PB7 via a four-wire bus.
Protection against polarity reversal is carried out on transistor T1, signaling of incorrect connection is carried out on elements VD1, EP1, R13. When the charger is connected to the network, transistor T1 is closed at a low level from the PC5 port, and the battery is disconnected from the charger. It connects only when you select the battery type and charger operating mode in the menu. This also ensures that there is no sparking when the battery is connected. If you try to connect the battery in the wrong polarity, the buzzer EP1 and the red LED VD1 will sound, signaling a possible accident.
During the charging process, the charging current is constantly monitored. If it becomes equal to zero (the terminals have been removed from the battery), the device automatically goes to the main menu, stopping the charge and disconnecting the battery. Transistor T2 and resistor R12 form a discharge circuit, which participates in the charge-discharge cycle of the desulfating charge and in the battery test mode. The discharge current of 0.01C is set using PWM from the PD5 port. The cooler automatically turns off when the charging current drops below 1.8A. The cooler is controlled by port PD4 and transistor VT1.
Resistor R8 is ceramic or wire, with a power of at least 10 W, R12 is also 10 W. The rest are 0.125W. Resistors R5, R6, R10 and R11 must be used with a tolerance of at least 0.5%. The accuracy of the measurements will depend on this. It is advisable to use transistors T1 and T1 as shown in the diagram. But if you have to select a replacement, then you need to take into account that they must open with a gate voltage of 5V and, of course, must withstand a current of at least 10A. For example, transistors marked 40N03GP, which are sometimes used in the same ATX format power supplies, in the 3.3V stabilization circuit.
LCD– WH1602 or similar, on the controller HD44780, KS0066 or compatible with them. Unfortunately, these indicators may have different pin locations, so you may have to design a printed circuit board for your instance
Electrical modification circuit for standard ATX
It is better to use precision resistors in the control circuit, as indicated in the description. When using trimmers, the parameters are not stable. tested from my own experience. When testing this charger, it carried out a full cycle of discharging and charging the battery (discharging to 10.8V and charging in training mode, it took about a day). The heating of the computer's ATX power supply is no more than 60 degrees, and that of the MK module is even less.
There were no problems with the setup, it started right away, it just needed some adjustment to the most accurate readings. After demonstrating the work of this charging machine to a friend who was a car enthusiast, an application was immediately received for the production of another copy. Author of the scheme - Slon , assembly and testing - sterc .
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