Analysis of more than 11 circuits for making a charger with your own hands at home, new circuits for 2017 and 2018, how to assemble a circuit diagram in an hour.
TEST:
To understand whether you have the necessary information about batteries and chargers for them, you should take a short test:- What are the main reasons why a car battery discharges on the road?
A) The motorist got out of the vehicle and forgot to turn off the headlights.
B) The battery has become too hot due to exposure to sunlight.
- Can the battery fail if the car is not used for a long time (sitting in a garage without starting)?
A) If left idle for a long time, the battery will fail.
B) No, the battery will not deteriorate, it will only need to be charged and it will function again.
- What current source is used to recharge the battery?
A) There is only one option - a network with a voltage of 220 volts.
B) 180 Volt network.
- Is it necessary to remove the battery when connecting a homemade device?
A) It is advisable to remove the battery from its installed location, otherwise there is a risk of damaging the electronics due to high voltage.
B) It is not necessary to remove the battery from its installed location.
- If you confuse “minus” and “plus” when connecting a charger, will the battery fail?
A) Yes, if connected incorrectly, the equipment will burn out.
B) The charger simply will not turn on; you will need to move the necessary contacts to the correct places.
Answers:
- A) Headlights not turned off when stopping and sub-zero temperatures are the most common causes of battery discharge on the road.
- A) The battery fails if it is not recharged for a long time when the car is idle.
- A) For recharging, a mains voltage of 220 V is used.
- A) It is not advisable to charge the battery with a homemade device if it is not removed from the car.
- A) The terminals should not be mixed up, otherwise the homemade device will burn out.
Battery on vehicles require periodic charging. The reasons for the discharge can be different - from headlights that the owner forgot to turn off, to negative temperatures outside in winter. For recharge battery You will need a good charger. This device is available in large varieties in auto parts stores. But if there is no opportunity or desire to purchase, then memory You can do it yourself at home. There are also a large number of schemes - it is advisable to study them all in order to choose the most suitable option.
Definition: A car charger is designed to transmit electric current with a given voltage directly to Battery
Answers to 5 Frequently Asked Questions
- Will I need to take any additional measures before charging the battery in my car?– Yes, you will need to clean the terminals, since acid deposits appear on them during operation. Contacts It needs to be cleaned very well so that current flows to the battery without difficulty. Sometimes motorists use grease to treat terminals; this should also be removed.
- How to wipe charger terminals?— You can buy a specialized product in a store or prepare it yourself. Water and soda are used as a self-made solution. The components are mixed and stirred. This is an excellent option for treating all surfaces. When the acid comes into contact with soda, a reaction will occur and the motorist will definitely notice it. This area will need to be thoroughly wiped to get rid of all acids. If the terminals were previously treated with grease, it can be removed with any clean rag.
- If there are covers on the battery, do they need to be opened before charging?— If there are covers on the body, they must be removed.
- Why is it necessary to unscrew the battery caps?— This is necessary so that the gases formed during the charging process can freely exit the case.
- Is there a need to pay attention to the electrolyte level in the battery?- This is done without fail. If the level is lower than required, then you need to add distilled water inside the battery. Determining the level is not difficult - the plates must be completely covered with liquid.
It’s also important to know: 3 nuances about operation
The homemade product differs somewhat in its method of operation from the factory version. This is explained by the fact that the purchased unit has built-in functions, helping in work. They are difficult to install on a device assembled at home, and therefore you will have to adhere to several rules when operation.
- A self-assembled charger will not turn off when the battery is fully charged. That is why it is necessary to periodically monitor the equipment and connect it to multimeter– for charge control.
- You need to be very careful not to confuse “plus” and “minus”, otherwise Charger will burn.
- The equipment must be turned off when connecting to charger.
By following these simple rules, you will be able to recharge correctly battery and avoid unpleasant consequences.
Top 3 charger manufacturers
If you don’t have the desire or ability to assemble it yourself memory, then pay attention to the following manufacturers:
- Stack.
- Sonar.
- Hyundai.
How to avoid 2 mistakes when charging a battery
It is necessary to follow the basic rules in order to properly nourish battery by car.
- Direct to mains battery connection is prohibited. Chargers are intended for this purpose.
- Even device it is made with high quality and from good materials, you will still need to periodically monitor the process charging, so that troubles don't happen.
Following simple rules will ensure reliable operation of self-made equipment. It is much easier to monitor the unit than to spend money on components for repairs.
The simplest battery charger
Scheme of a 100% working 12 volt charger
Look at the picture for the diagram memory at 12 V. The equipment is intended for charging car batteries with a voltage of 14.5 Volts. The maximum current received during charging is 6 A. But the device is also suitable for other batteries - lithium-ion, since the voltage and output current can be adjusted. All the main components for assembling the device can be found on the Aliexpress website.
Required components:
- dc-dc buck converter.
- Ammeter.
- Diode bridge KVRS 5010.
- Hubs 2200 uF at 50 volts.
- transformer TS 180-2.
- Circuit breakers.
- Plug for connecting to the network.
- "Crocodiles" for connecting terminals.
- Radiator for diode bridge.
Transformer any one can be used at your own discretion. The main thing is that its power is not lower than 150 W (with a charging current of 6 A). It is necessary to install thick and short wires on the equipment. The diode bridge is fixed on a large radiator.
Look at the picture of the charger circuit Dawn 2. It is compiled according to the original Memory If you master this scheme, you will be able to independently create a high-quality copy that is no different from the original sample. Structurally, the device is a separate unit, closed with a housing to protect the electronics from moisture and exposure to bad weather conditions. It is necessary to connect a transformer and thyristors on the radiators to the base of the case. You will need a board that will stabilize the current charge and control the thyristors and terminals.
1 smart memory circuit
Look at the picture for a circuit diagram of a smart charger. The device is necessary for connection to lead-acid batteries with a capacity of 45 amperes per hour or more. This type of device is connected not only to batteries that are used daily, but also to those on duty or in reserve. This is a fairly budget version of the equipment. It does not provide indicator, and you can buy the cheapest microcontroller.
If you have the necessary experience, then you can assemble the transformer yourself. There is also no need to install audible warning signals - if battery connects incorrectly, the discharge lamp will light up to indicate an error. The equipment must be equipped with a switching power supply of 12 volts - 10 amperes.
1 industrial memory circuit
Look at the industrial diagram charger from Bars 8A equipment. Transformers are used with one 16-volt power winding, several vd-7 and vd-8 diodes are added. This is necessary in order to provide a bridge rectifier circuit from one winding.
1 inverter device diagram
Look at the picture for a diagram of an inverter charger. This device discharges the battery to 10.5 Volts before charging. The current is used with a value of C/20: “C” indicates the capacity of the installed battery. After that process the voltage rises to 14.5 Volts using a discharge-charge cycle. The ratio of charge and discharge is ten to one.
1 electrical circuit charger electronics
1 powerful memory circuit
Look at the picture at the diagram of a powerful charger for a car battery. The device is used for acidic battery, having high capacity. The device easily charges a car battery with a capacity of 120 A. The output voltage of the device is self-regulated. It ranges from 0 to 24 volts. Scheme It is notable for the fact that it has few components installed, but it does not require additional settings during operation.
Many could already see the Soviet Charger. It looks like a small metal box and may seem quite unreliable. But this is not true at all. The main difference between the Soviet model and modern models is reliability. The equipment has structural capacity. In the event that to the old device connect the electronic controller, then charger it will be possible to revive. But if you no longer have one at hand, but there is a desire to assemble it, you need to study the diagram.
To the features their equipment includes a powerful transformer and rectifier, with the help of which it is possible to quickly charge even a very discharged battery. Many modern devices will not be able to reproduce this effect.
Electron 3M
In an hour: 2 DIY charging concepts
Simple circuits
1 the simplest scheme for an automatic charger for a car battery
How often do car owners fail to start a four-wheeled pet due to lack of charge in the battery? Of course, if this incident happened in the garage near the charging unit or there is a friend with a car nearby who is ready to help start the starter, no special problems are expected.
The situation is much worse if you cannot implement either the first or second option, especially motorists who do not have the opportunity to purchase an expensive factory-made charger suffer from this. But even in this case, you can find a solution if you make a charger for a car battery with your own hands.
Advantages and disadvantages of a homemade device
The main advantage of a homemade charger is its low cost, even if you do not have all the necessary parts, the savings will be noticeable. Also a significant advantage is the ability to use unnecessary instruments and devices as a source of materials for a homemade memory.
The disadvantages of homemade battery charging include imperfection in operation. Alas, the model cannot turn off on its own when the maximum charge is reached, so you will have to control this process or supplement the invention with homemade automation, which is possible for experienced radio amateurs.
Device settings
As you well know, the entire network in the car is powered by low voltage 12V DC, but the charging level of the car battery should be in the range of 13 to 15V. The charge current at the device output should be about 10% of the power source capacity. If the current is less, the charge will still occur, but the procedure will last much longer. Therefore, the choice of elements for the charger should be based on the operating parameters of the specific model of lead-acid battery and the network to which it will be connected.
What is needed for the memory?
Structurally, the charger includes the following elements:
Rice. 2: Example of setting the adjustment resistor If you are going to charge the battery once, you can use only the first three elements; for constant use it will be more convenient to have at least control devices. But before you put it all together, you need to make sure that the charger's parameters after assembly will meet your needs. The first thing that needs to match is the charger transformer.
If the transformer is not suitable
Not always in a garage or at home you will find just such a transformer that will be powered by 220V and output 13 - 15V at the output terminals. Most models used in everyday life do have a 220V primary coil, but the output can be of any value. To fix this you will need to make a new secondary.
First, recalculate the transformation ratio using the formula: U 1 / U 2 = N 1 / N 2,
N 1 and N 2 – the number of turns in the primary and secondary, respectively.
For example, an electric machine is used as a 42V power supply, but you want to get 14V for the charger. Therefore, you need to make 31 turns on the charger secondary with 480 turns in the primary. This can be achieved either by reducing the number of turns, removing unnecessary ones, or by winding a new one. But the first option is not always suitable, since the cross-section of the transformer winding may not withstand the current with a smaller number of turns.
U 1 *I 1 = U 2 *I 2 ,
Where U 1 and U 2 are the voltage on the primary and secondary windings, I 1 and I 2 are the current flowing in the primary and secondary.
As you can see, with a decrease in the number of turns and voltage on the secondary winding, the current strength in it will increase proportionally. As a rule, the cross-sectional margin is not enough, so after determining the current strength, a new conductor is selected for it from the data in the table:
Table: selection of cross section, depending on the flowing current
| Copper conductor | Aluminum conductor | ||
| Section
lived mm 2 |
Current, A | Section of veins. mm 2 | Current, A |
| 0,5 | 11 | — | — |
| 0,75 | 15 | — | — |
| 1 | 17 | — | — |
| 1.5 | 19 | 2,5 | 22 |
| 2.5 | 27 | 4 | 28 |
| 4 | 38 | 6 | 36 |
| 6 | 46 | 10 | 50 |
| 10 | 70 | 16 | 60 |
| 16 | 80 | 25 | 85 |
If the calculated current value at the output of the charger exceeds the required 10% of the battery capacity, a current-limiting resistor must be included in the circuit, the value of which is selected in proportion to the excess current.
The procedure for assembling a charger for a car battery
Depending on the components you have and the battery parameters, the charger assembly will vary significantly. In this example, the manufacturing technology includes the following steps:
But you must start from the parameters of your electric machine. Therefore, if necessary, remove excess windings or insulate their terminals (if any), wind a secondary (if the existing one does not provide the required voltage level in the memory).
Rice. 5: Rewind the windings 
and on the secondary there are pins 9 and 9′.
Rice. 7: connect pins 9 - Solder the power cord leads to terminals 2 and 2′.
Rice. 8: Connect the power cord - Assemble the diode assembly on a textolite plate, as shown in the diagram. Due to intense heat generation due to high charging currents, semiconductor devices are installed on a radiator.
Rice. 9: diode assembly - Connect the bridge to the 12V terminals, in this example these are terminals 10 and 10′. The main elements of the charger are assembled.
Rice. 10: connect pins 10 to the diode bridge - Install an ammeter with a measurement limit of up to 15 A between the diode bridge terminal and the battery terminals.
Rice. 11: connect the ammeter - Connect a current-limiting block of resistors or a switch with a resistance adjustment function to the ammeter circuit; they will allow you to change the value of the charger current. Rice. 13: Connect the voltmeter
To protect the charger, both on the mains side and on the lead battery side, you need to install two fuses. In the example under consideration, a 0.5A fuse is used on the high side of the charger, and a 10A fuse is used in the lead-acid battery charging circuit.
If you have a charger current regulator, you should start charging from the minimum value on the ammeter and gradually increase it to the required value. When a sufficient amount of charge has accumulated in the battery, the ammeter will show about 1A, after which you can safely disconnect the charger from the mains and use the battery for its intended purpose.
Rice. 14: dependence of values on charging time Video on the topic
The topic of car chargers is of interest to many people. From this article you will learn how to convert a computer power supply into a full-fledged charger for car batteries. It will be a pulse charger for batteries with a capacity of up to 120 Ah, that is, charging will be quite powerful.
There is practically no need to assemble anything - you just need to remake the power supply. Only one component will be added to it.
A computer power supply has several output voltages. The main power buses have voltages of 3.3, 5 and 12 V. Thus, for the device to operate, you will need a 12-volt bus (yellow wire).
To charge car batteries, the output voltage should be around 14.5-15 V, therefore, 12 V from a computer power supply is clearly not enough. Therefore, the first step is to raise the voltage on the 12-volt bus to a level of 14.5-15 V.
Then, you need to assemble an adjustable current stabilizer or limiter so that you can set the required charge current.
The charger, one might say, will be automatic. The battery will be charged to the specified voltage with a stable current. As the charge progresses, the current will drop, and at the very end of the process it will be equal to zero.
When starting to manufacture a device, you need to find a suitable power supply. For these purposes, blocks containing the TL494 PWM controller or its full-fledged analogue K7500 are suitable.
When the required power supply is found, you need to check it. To start the unit, you need to connect the green wire to any of the black wires.
If the unit starts up, you need to check the voltage on all buses. If everything is in order, then you need to remove the board from the tin case.
After removing the board, you need to remove all the wires except two black, two green and go to start the unit. It is recommended to solder the remaining wires with a powerful soldering iron, for example, 100 W.
This step will require your full attention, as this is the most important point in the entire remodel. You need to find the first pin of the microcircuit (in the example there is a 7500 chip), and find the first resistor that is applied from this pin to the 12 V bus.
There are many resistors located on the first pin, but finding the right one will not be difficult if you test everything with a multimeter.
After finding the resistor (in the example it is 27 kOhm), you need to unsolder only one pin. To avoid confusion in the future, the resistor will be called Rx.
Now you need to find a variable resistor, say 10 kOhm. Its power is not important. You need to connect 2 wires about 10 cm long each in this way:
One of the wires must be connected to the soldered terminal of the Rx resistor, and the second must be soldered to the board in the place from which the terminal of the Rx resistor was soldered. Thanks to this adjustable resistor, it will be possible to set the required output voltage.
A charge current stabilizer or limiter is a very important addition that should be included in every charger. This unit is made on the basis of an operational amplifier. Almost any “ops” will do here. The example uses the budget LM358. There are two elements in the body of this microcircuit, but only one of them is needed.
A few words about the operation of the current limiter. In this circuit, an op-amp is used as a comparator that compares the voltage across a low-value resistor to a reference voltage. The latter is set using a zener diode. And the adjustable resistor now changes this voltage.
When the voltage value changes, the op amp will try to smooth out the voltage at the inputs and will do this by decreasing or increasing the output voltage. Thus, the “op-amp” will control the field-effect transistor. The latter regulates the output load.
A field-effect transistor needs a powerful one, since all the charging current will pass through it. The example uses IRFZ44, although any other appropriate parameter can be used.
The transistor must be installed on a heat sink, because at high currents it will heat up quite well. In this example, the transistor is simply attached to the power supply housing.
The printed circuit board was wired hastily, but it turned out pretty good.
Now all that remains is to connect everything according to the picture and begin installation.
The voltage is set to around 14.5 V. The voltage regulator does not need to be brought outside. For control on the front panel there is only a charge current regulator, and a voltmeter is also not needed, since the ammeter will show everything that needs to be seen when charging.
You can take a Soviet analog or digital ammeter.
Also on the front panel was a toggle switch for starting the device and output terminals. The project can now be considered complete.
The result is an easy-to-manufacture and inexpensive charger that you can safely replicate yourself.
Attached files:
Compliance with the operating mode of rechargeable batteries, and in particular the charging mode, guarantees their trouble-free operation throughout their entire service life. 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 charger for a car battery consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats (see Fig. 1) and transistor current stabilizers are used as current regulators.
In both cases, these elements generate significant thermal power, which reduces the efficiency of the charger and increases the likelihood of its failure.
To regulate the charging current, you can use a store of capacitors connected in series with the primary (mains) winding of the transformer and acting as reactances that dampen excess network 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 insignificant.
The disadvantage in Fig. 2 is the need to provide a voltage on the secondary winding of the transformer one and a half times greater than the rated load voltage (~ 18÷20V).
The charger circuit, which 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.
Switches Q1 - Q4 can be used to connect various combinations of capacitors and thereby regulate the charging current.
The variable resistor R4 sets the response threshold of K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.
In Fig. Figure 4 shows another charger in which the charging current is smoothly regulated from zero to the maximum value.
The change in current in the load is achieved by adjusting the opening angle of the thyristor 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. The maximum battery charging current is 10A, set with an ammeter. The device is provided on the mains and load side with fuses F1 and F2.
A version of the charger printed circuit board (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 greater than the charging current, and accordingly, the power of the transformer must also be three times greater than the power consumed by the battery.
This circumstance is a significant drawback of chargers with a current regulator thyristor (thyristor).
Note:
The rectifier bridge diodes VD1-VD4 and the thyristor VS1 must be installed on radiators.
It is possible to significantly reduce power losses in the SCR, and therefore increase the efficiency of the charger, by moving the control element from the circuit of the secondary winding of the transformer to the circuit of the primary winding. such a device is shown in Fig. 5.
In the diagram in Fig. 5 control unit is similar to that used in the previous version of the device. SCR VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is approximately 10 times less than the charging current, relatively little thermal power is released on the diodes VD1-VD4 and the thyristor VS1 and they do not require installation on radiators. In addition, the use of an SCR in the primary winding circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the current curve shape coefficient (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 a design (for example, use a variable resistor with a plastic axis).
A version of the printed circuit board of the charger in Figure 5, measuring 60x75 mm, is shown in the figure below:
Note:
The rectifier bridge diodes VD5-VD8 must be installed on radiators.
In the charger in Figure 5 there is a diode bridge VD1-VD4 type KTs402 or KTs405 with the letters A, B, C. Zener diode VD3 type KS518, KS522, KS524, or made up of two identical zener diodes with a total stabilization voltage of 16÷24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is unijunction, type KT117A, B, V, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247, etc.). The diodes are installed on radiators with an area of at least 200 sq.cm, and the radiators will become very hot; a fan can be installed in the charger case for ventilation.
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 manually for a specific battery or you can select those already included in the control program.Basic operating modes of the device for the presets included in the program.
>>
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.
>>
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 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).
Charging circuit diagram for 12V battery
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, 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, in which all the algorithms are embedded. 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
Converting an ATX power supply to a charger
Electrical circuit for modification of 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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