Simple automatic charger. How to make an automatic charger for a car battery with your own hands. Disconnecting the charger when fully charged; diagram

The article describes car battery charger, which allows you to set the charging current up to 10 A and automatically turn off battery charging when the set voltage on it is reached. The article provides schematic diagrams and drawingsinstallation of parts,printed circuit board, device design and dana me procedure for setting it up.

Most chargers allow you to set only the required charge current. In simple devices this current is maintained manually, and in some devices it is maintained automatically by current stabilizers. When using such devices, it is necessary to monitor the process of charging the battery to the maximum permissible voltage, which requires appropriate time and attention. The fact is that overcharging the battery leads to boiling of the electrolyte, which shortens its service life. The proposed charger allows you to set the charge current and automatically turn it off when the set voltage value is reached

The charger is built on the basis of an industrial rectifier type VSA-6K (you can use any rectifier of suitable power), converting an alternating voltage of 220 V into a fixed direct voltage of 12 V and 24 B, which are switched by a packet switch. The rectifier is designed for load current up to 24 A and does not contain an anti-aliasing filter. To charge batteries, the rectifier is supplemented with an electronic control circuit that allows you to set the required charging current and the rated voltage for disconnecting the charger from the battery when fully charged.

The charger is mainly intended for charging car batteries voltage 12 V and charging current up to 10 A, and can also be used for other purposes. To charge these batteries, a rectified voltage of 24 V is used, and for batteries with a voltage of 6 V, a voltage of 12 V is used. A smoothing filter cannot be connected to the output of the rectifier, since the thyristor can close only when the voltage reaches zero, and open at the right moment by the control circuit.

Fig. 1 Diagram of the power part of the charger

Schematic diagram of connection rectifier VSA-6K to the electronic control circuit board and to external elements is shown in Fig. 1. The terminals of the charger for connecting the battery are connected to the standard terminals of the front panel of the rectifier X3 and X4. To use fixed DC voltages of 12 V or 24 V when using the device for other purposes, the standard rectifier leads are connected to screw terminals XI and X2 located on the insulating strip next to the fuse FU2, which are covered by a removable cover on the right side wall of the device.

The rectifier voltmeter is connected to the battery connection terminals. The ammeter remains connected to the common “+” circuit and measures both the battery charge current and the load current connected to terminals X1 and X2. Voltage is supplied to the control circuit only when the battery is connected.

Commercially available batteries are usually charged and filled with electrolyte or dry-charged without electrolyte. They only require recharging to rated capacity. Used car batteries also require recharging after maintenance or long periods of inactivity. If it becomes necessary to form and charge a battery from scratch, then initially it must be recharged from a source with a fixed voltage of 12 V through a rheostat, which sets the required charging current. After the battery voltage reaches about 10 V, further operations can be performed by connecting it to terminals X3, X4.

For the subsequent description of the operation of the charger, it should be briefly recalled that the acid batteries used in passenger cars contain six cells. When the voltage on the bank reaches 2.4 V, gas evolution of an explosive oxygen-hydrogen mixture begins, which indicates that the battery is fully charged. Gas evolution destroys the active mass contained in the lead battery plates, therefore, to ensure maximum battery life, the voltage on each element should not exceed 2.3 V on average, also taking into account that the internal resistances of the elements and the voltages on them may differ slightly from each other friend. This ultimately corresponds to a maximum battery voltage of 13.8V, at which the charger should automatically turn off.

Device operation

The control circuit diagram is shown in Fig. 2,installation of parts is shown in Fig. 3, and the printed circuit board is shown in Fig. 4. The control circuit consists of a constant voltage amplifier on transistors VT1, VT2, VT3 and a circuit with an analogue of a unijunction transistor on VT4 and VT5, which controls the thyristor VS1 to set the required charging current. Using an analogue instead of a conventional unijunction transistor (for example, KT117A-G) is advantageous in that by choosing transistors and resistors R9 - R1 1 you can select its necessary characteristics.

When the battery voltage is less than 13.8 V, transistor VT3 is closed, and VT2 and VT1 are open. Pin 6 of the control board receives positive half-voltage waves from the diode bridge of the rectifier, which are superimposed on the constant voltage of the battery and, through open VT1, VD1, R8, are supplied to the thyristor current regulator.

Fig.2 Control diagram

It works as follows: voltage from R8 is supplied to the base VT4 and through the charging current setting regulator R12 to capacitor C1.

At the initial moment, VT4 and VT5 are closed. When C1 is charged to the operating voltage of an analogue of a unijunction transistor, a pulse is sent from the emitter VT5 to the control electrode of the thyristor, which opens and closes the battery charging circuit. In this case, C1 is quickly discharged through the low resistance of the open analogue of the unijunction transistor. When the next pulse arrives, the process repeats. The lower the resistance value R12 (Fig. 1), the faster C1 charges and VS1 opens, as a result of which it remains in the open state longer, and the greater the charging current. The glow of VD1 indicates that the battery is charging.

When the battery voltage reaches 13.8 IN, which corresponds to its full charge, transistor VT3 opens, and VT2 and VT1 close, the voltage on the thyristor control circuit disappears, the battery charge stops and the VD1 LED goes out.

Setting up the device

Setting up the charger is carried out with its front panel open and consists of setting the charging current cut-off voltage. To do this, you need to connect a voltmeter with an accuracy class of at least 1.5 to the battery, make sure that there is a voltage on it of at least 10.8 V (discharging a 12 V acid battery to a voltage below 10.8 V is not allowed), set the charging current (value 0.1 battery capacity), and set the trimmer resistor R5 to the middle position and start charging. If the charger turns off when the battery voltage is less than 13.8 V, then the slider of resistor R5 must be turned at a certain angle counterclockwise until the LED lights up and continue charging to 13.8 V, and if the device does not turn off at this voltage, turn the slider clockwise until the device turns off. In this case, the LED should go out. This completes the setup of the circuit and the front panel is installed in its place. For further operation of the charger, it is necessary to note which position of the needle on the standard voltmeter corresponds to a voltage of 13.8 V, so as not to use an additional voltmeter.

Fig.3

Fig.4

Fig.5

Structurally, the control board, thyristor with cooler, LED VD1 and variable resistor R12 for setting the charging current are fixed on the inside of the front panel (Fig. 5). The thyristor radiator is fixed on the panel using two textolite strips. It is attached to one with two M3 countersunk screws, and the other serves as an insulating gasket. The control board is secured with an additional nut at the ammeter terminal, which should not touch its printed tracks.

In conclusion, it should be noted that this device can provide a charging current of up to 24 A when installing a more powerful thyristor and fuse FU2 for a current of 25 A.

Anatoly Zhurenkov

Literature

1. S. Elkin Application of thyristor regulators with phase-pulse control // Radioammator. - 1998.-No.9.-P.37-38.

2. V. Voevoda Simple thyristor charger // Radio. - 2001. - No. 11. - P.35.

The device is designed to charge a 6-volt sealed lead battery of a children's electric motorcycle, but with minimal modifications it can be used to charge other types of batteries (batteries), with any voltage, for which the condition for the end of the charge is to reach a certain voltage level. In this device, battery charging stops when the terminal voltage reaches 7.3V. The charge is carried out with an unstabilized current, limited at 0.1C by resistor R6. The voltage level at which the device stops charging is set by the zener diode VD1 accurate to tenths of a volt.

The “heart” of the circuit is an operational amplifier (op-amp), connected as a comparator, and connected by an inverting input to a reference voltage source (chain R1-VD1), and not by an inverting input to the battery. As soon as the voltage on the battery exceeds the reference voltage, the comparator switches to the single state, transistor T1 opens and relay REL1 disconnects the battery from the voltage source, while simultaneously applying a positive voltage to the base of transistor T1. Thus, T1 will be open and its state will no longer depend on the voltage level at the output of the comparator. The comparator itself is covered by positive feedback (R7), which creates hysteresis and leads to a sharp, abrupt switching of the output and opening of the transistor. Thanks to this, the circuit is free from the disadvantage of similar devices with a mechanical relay, in which the relay makes an unpleasant rattling sound due to the fact that the contacts are balancing at the switching boundary, but switching on has not yet occurred. In the event of a power outage, the device will resume operation as soon as it appears and will not allow the battery to be overcharged.

The device is assembled from available parts, starts working immediately, and does not require configuration. The shutdown voltage depends only on the parameters of the zener diode. The op-amp indicated in the diagram can operate in the supply voltage range from 3 to 30 volts, and when connecting a battery with a different voltage, for example 12V, it is necessary to select a zener diode for the voltage of the charged battery (14.4V).

The device is assembled according to the circuit diagram and drawing of the printed circuit board, tested in operation.

List of radioelements

An automatic car battery charger consists of a power supply and protection circuits. You can assemble it yourself if you have electrical installation skills. During assembly, both complex electrical circuits and simpler versions of the device are designed.

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Requirements for homemade chargers

In order for the charger to automatically restore the car battery, strict requirements are imposed on it:

1. Any simple modern memory device must be autonomous. Thanks to this, the operation of the equipment does not have to be monitored, in particular if it operates at night. The device will independently control the operating parameters of voltage and charge current. This mode is called automatic.
2. The charging equipment must independently provide a stable voltage level of 14.4 volts. This parameter is necessary to restore any batteries operating in a 12-volt network.
3. The charging equipment must ensure irreversible disconnection of the battery from the device under two conditions. In particular, if the charge current or voltage increases by more than 15.6 volts. The equipment must have a self-locking function. To reset the operating parameters, the user will have to turn off and activate the device.
4. The equipment must be protected from overvoltage, otherwise the battery may fail. If the consumer confuses the polarity and incorrectly connects the negative and positive contacts, a short circuit will occur. It is important that charging equipment provides protection. The circuit is supplemented with a safety device.
5. To connect the charger to the battery, you will need two wires, each of which must have a cross-section of 1 mm2. An alligator clip must be installed on one end of each conductor. On the other side, split tips are installed. The positive contact must be made in a red sheath, and the negative contact in a blue sheath. For a household network, a universal cable equipped with a plug is used.

If you completely make the device yourself, failure to comply with the requirements will harm not only the charger, but also the battery.

Vladimir Kalchenko spoke in detail about the modification of the charger and the use of wires suitable for this purpose.

Automatic charger design

The simplest example of a charger structurally includes the main part - a step-down transformer device. This element reduces the voltage parameter from 220 to 13.8 volts, which is required to restore the battery charge. But the transformer device can only reduce this value. And the conversion of alternating current to direct current is carried out by a special element - a diode bridge.

Each charger must be equipped with a diode bridge, since this part rectifies the current value and allows it to be divided into positive and negative poles.

In any circuit, an ammeter is usually installed behind this part. The component is designed to demonstrate current strength.

The simplest designs of chargers are equipped with pointer sensors. More advanced and expensive versions use digital ammeters, and in addition to them, the electronics can be supplemented with voltmeters.

Some device models allow the consumer to change the voltage level. That is, it becomes possible to charge not only 12-volt batteries, but also batteries designed to operate in 6- and 24-volt networks.

Wires with positive and negative terminals extend from the diode bridge. They are used to connect equipment to the battery. The entire structure is enclosed in a plastic or metal case, from which comes a cable with a plug for connecting to the electrical network. Also, two wires with a negative and positive terminal clamp are output from the device. To ensure safer operation of the charging equipment, the circuit is supplemented with a fusible safety device.

User Artem Kvantov clearly disassembled the proprietary charging device and talked about its design features.

Automatic charger circuits

If you have skills in working with electrical equipment, you can assemble the device yourself.

Simple circuits

These types of devices are divided into:

• devices with one diode element;
• equipment with a diode bridge;
• devices equipped with smoothing capacitors.

Circuit with one diode

There are two options here:

1. You can assemble a circuit with a transformer device and install a diode element after it. At the output of the charging equipment, the current will be pulsating. Its beats will be serious, since one half-wave is actually cut off.
2. You can assemble the circuit using a laptop power supply. It uses a powerful rectifying diode element with a reverse voltage of more than 1000 volts. Its current must be at least 3 amperes. The outer terminal of the power plug will be negative and the inner terminal will be positive. Such a circuit must be supplemented with a limiting resistance, which can be used as a light bulb to illuminate the interior.

It is permissible to use a more powerful lighting device from a turn signal, side lights or brake lights. When using a laptop power supply, this may cause it to overload. If a diode is used, then an incandescent lamp of 220 volts and 100 watts must be installed as a limiter.

When using a diode element, a simple circuit is assembled:

1. First comes the terminal from a 220-volt household outlet.
2. Then - the negative contact of the diode element.
3. The next one will be the positive terminal of the diode.
4. Then a limiting load is connected - a lighting source.
5. Next will be the negative terminal of the battery.
6. Then the positive terminal of the battery.
7. And the second terminal for connecting to a 220-volt network.

When using a 100-watt light source, the charging current will be approximately 0.5 amperes. So in one night the device will be able to transfer 5 A/h to the battery. This is enough to turn the vehicle's starter mechanism.

To increase the indicator, you can connect three 100-watt lighting sources in parallel; this will replenish half the battery capacity overnight. Some users use electric stoves instead of lamps, but this cannot be done, since not only the diode element will fail, but also the battery.

The simplest circuit with one diode Electrical diagram for connecting the battery to the network

Circuit with diode bridge

This component is designed to “wrap” the negative wave upward. The current itself will also pulsate, but its beats are much less. This version of the scheme is used more often than others, but is not the most effective.

You can make a diode bridge yourself using a rectifying element, or purchase a ready-made part.

Electrical circuit of a charger with a diode bridge

Circuit with smoothing capacitor

This part should be rated for 4000-5000 uF and 25 volts. A direct current is generated at the output of the resulting electrical circuit. The device must be supplemented with 1 ampere safety elements, as well as measuring equipment. These parts allow you to control the battery recovery process. You don’t have to use them, but then you will need to connect a multimeter periodically.

While monitoring voltage is convenient (by connecting terminals to probes), monitoring current will be more difficult. In this operating mode, the measuring device will have to be connected to an electrical circuit. The user will need to turn off the power from the network each time and put the tester in current measurement mode. Then turn on the power and disassemble the electrical circuit. Therefore, it is recommended to add at least one 10 amp ammeter to the circuit.

The main disadvantage of simple electrical circuits is the lack of ability to adjust the charging parameters.

When selecting the element base, you should select operating parameters so that the output current is 10% of the total battery capacity. A slight decrease in this value is possible.

If the resulting current parameter is greater than required, the circuit can be supplemented with a resistor element. It is installed on the positive output of the diode bridge, immediately before the ammeter. The resistance level is selected in accordance with the bridge used, taking into account the current indicator, and the power of the resistor should be higher.

Electrical circuit with a smoothing capacitor device

Circuit with the ability to manually adjust the charge current for 12 V

To make it possible to change the current parameter, it is necessary to change the resistance. A simple way to solve this problem is to install a variable trimmer resistor. But this method cannot be called the most reliable. To ensure higher reliability, it is necessary to implement manual adjustment with two transistor elements and a trimming resistor.

Using a variable resistor component, the charging current will vary. This part is installed after the composite transistor VT1-VT2. Therefore, the current through this element will be low. Accordingly, the power will also be small, it will be about 0.5-1 W. The operating rating depends on the transistor elements used and is selected experimentally; the parts are designed for 1-4.7 kOhm.

The circuit uses a 250-500 W transformer device, as well as a secondary winding of 15-17 volts. The diode bridge is assembled on parts whose operating current is 5 amperes or more. Transistor elements are selected from two options. These can be germanium parts P13-P17 or silicon devices KT814 and KT816. To ensure high-quality heat removal, the circuit must be placed on a radiator device (at least 300 cm3) or a steel plate.

At the output of the equipment, a safety device PR2 is installed, rated at 5 amperes, and at the input - PR1 at 1 A. The circuit is equipped with signal light indicators. One of them is used to determine the voltage in a 220 volt network, the second is used to determine the charging current. It is allowed to use any lighting sources rated for 24 volts, including diodes.

Electrical circuit for a charger with manual adjustment function

Over-reversal protection circuit

There are two options for implementing such a memory:

• using relay P3;
• by assembling a charger with integral protection, but not only from overvoltage, but also from overvoltage and overcharging.

With relay P3

This version of the circuit can be used with any charging equipment, both thyristor and transistor. It must be included in the cable break through which the battery is connected to the charger.

Scheme for protecting equipment from reverse polarity on relay P3

If the battery is not connected to the network correctly, the VD13 diode element will not pass current. The electrical circuit relay is de-energized and its contacts are open. Accordingly, current will not be able to flow to the battery terminals. If the connection is made correctly, the relay is activated and its contact elements are closed, so the battery is charged.

With integrated overvoltage, overcharge and overvoltage protection

This version of the electrical circuit can be built into an already used homemade power source. It uses the slow response of the battery to a voltage surge, as well as relay hysteresis. The voltage with the release current will be 304 times less than this parameter when triggered.

An AC relay is used with an activation voltage of 24 volts, and a current of 6 amperes flows through the contacts. When the charger is activated, the relay turns on, the contact elements close and charging begins.

The voltage parameter at the output of the transformer device drops below 24 volts, but at the output of the charger there will be 14.4 V. The relay must maintain this value, but when an extra current appears, the primary voltage will drop even more. This will turn off the relay and break the charging circuit.

The use of Schottky diodes in this case is impractical, since this type of circuit will have serious disadvantages:

1. There is no protection against voltage surges across the contact if the battery is completely discharged.
2. There is no self-locking of the equipment. As a result of exposure to extra current, the relay will turn off until the contact elements fail.
3. Unclear operation of equipment.

Because of this, adding a device to this circuit to adjust the operating current does not make sense. The relay and transformer device are precisely matched to each other so that the repeatability of the elements is close to zero. The charging current passes through the closed contacts of relay K1, as a result of which the likelihood of their failure due to burning is reduced.

Winding K1 must be connected according to a logical electrical circuit:

• to the overcurrent protection module, these are VD1, VT1 and R1;
• to the surge protection device, these are elements VD2, VT2, R2-R4;
• as well as to the self-locking circuit K1.2 and VD3.

Circuit with integrated protection against overvoltage, overcharge and overvoltage

The main disadvantage is the need to set up a circuit using a ballast load, as well as a multimeter:

1. Elements K1, VD2 and VD3 are desoldered. Or you don’t have to solder them during assembly.
2. The multimeter is activated, which must be configured in advance to measure a voltage of 20 volts. It must be connected instead of winding K1.
3. The battery is not connected yet; a resistor device is installed instead. It should have a resistance of 2.4 ohms for a charge current of 6 A or 1.6 ohms for 9 amperes. For 12 A, the resistor should be rated at 1.2 Ohms and no less than 25 W. The resistor element can be wound from a similar wire that was used for R1.
4. A voltage of 15.6 volts is supplied to the input from the charging equipment.
5. The current protection should operate. The multimeter will show voltage since the resistance element R1 is selected with a slight excess.
6. The voltage parameter is reduced until the tester shows 0. The output voltage value must be recorded.
7. Then part VT1 is desoldered, and VD2 and K1 are installed in place. R3 must be placed in the lowest position in accordance with the electrical diagram.
8. The voltage of the charging equipment increases until the load reaches 15.6 volts.
9. Element R3 rotates smoothly until K1 is triggered.
10. The charger voltage is reduced to the value that was previously recorded.
11. Elements VT1 and VD3 are installed and soldered back. After this, the electrical circuit can be checked for functionality.
12. A working but dead or undercharged battery is connected through an ammeter. A tester must be connected to the battery, which is pre-configured to measure voltage.
13. The test charge must be carried out with continuous monitoring. At the moment when the tester shows 14.4 volts on the battery, it is necessary to detect the content current. This parameter should be normal or close to the lower limit.
14. If the content current is high, the charger voltage should be reduced.

Automatic shutdown circuit when the battery is fully charged

The automation must be an electrical circuit equipped with a power supply system for an operational amplifier and a reference voltage. For this, a DA1 class 142EN8G stabilizer board for 9 volts is used. This circuit must be designed so that the output voltage level remains virtually unchanged when measuring the board temperature by 10 degrees. The change will be no more than hundredths of a volt.

In accordance with the description of the circuit, the automatic deactivation system when the voltage increases by 15.6 volts is done on half of the A1.1 board. Its fourth pin is connected to the voltage divider R7 and R8, from which a reference value of 4.5V is supplied. The operating parameter of the resistor device sets the activation threshold of the charger to 12.54 V. As a result of using the diode element VD7 and part R9, it is possible to provide the desired hysteresis between the activation and shutdown voltages of the battery charge.

Electrical circuit of the charger with automatic deactivation when the battery is charged

The description of the action of the scheme is as follows:

1. When a battery is connected, the voltage level at the terminals of which is less than 16.5 volts, a parameter is set at the second terminal of circuit A1.1. This value is enough for the transistor element VT1 to open.
2. This detail is being discovered.
3. Relay P1 is activated. As a result, the primary winding of the transformer device is connected to the network through a block of capacitor mechanisms via contact elements.
4. The process of replenishing the battery charge begins.
5. When the voltage level increases to 16.5 volts, this value at output A1.1 will decrease. The decrease occurs to a value that is not enough to maintain the transistor device VT1 in the open state.
6. The relay is switched off and contact elements K1.1 are connected to the transformer unit through the capacitor device C4. With it, the charge current will be 0.5 A. In this state, the equipment circuit will operate until the voltage on the battery drops to 12.54 volts.
7. After this happens, the relay is activated. The battery continues to charge at the user-specified current. This circuit implements the ability to disable the automatic adjustment system. For this purpose, switching device S2 is used.

This operating procedure for an automatic charger for a car battery helps prevent its discharge. The user can leave the equipment turned on for at least a week, this will not harm the battery. If the voltage in the household network is lost, when it returns, the charger will continue to charge the battery.

If we talk about the principle of operation of the circuit assembled on the second half of the A1.2 board, then it is identical. But the level of complete deactivation of charging equipment from the power supply will be 19 volts. If the voltage is less, at the eighth output of board A1.2 it will be sufficient to hold the transistor device VT2 in the open position. With it, current will be supplied to relay P2. But if the voltage is more than 19 volts, then the transistor device will close and the contact elements K2.1 will open.

Required materials and tools

Description of parts and elements that will be required for assembly:

1. Power transformer device T1 class TN61-220. Its secondary windings must be connected in series. You can use any transformer whose power is no more than 150 watts, since the charging current is usually no more than 6A. The secondary winding of the device, when exposed to an electric current of up to 8 amperes, should provide a voltage in the range of 18-20 volts. If a ready-made transformer is not available, parts of similar power can be used, but the secondary winding will need to be rewinded.
2. Capacitor elements C4-C9 must comply with the MGBC class and have a voltage of at least 350 volts. Any type of device can be used. The main thing is that they are intended to operate in alternating current circuits.
3. Any diode elements VD2-VD5 can be used, but they must be rated for a current of 10 amperes.
4. Parts VD7 and VD11 are flint impulse.
5. Diode elements VD6, VD8, VD10, VD5, VD12, VD13 must withstand a current of 1 ampere.
6. LED element VD1 - any.
7. As a VD9 part, it is allowed to use a device of class KIPD29. The main feature of this light source is the ability to change color if the polarity of the connection is changed. To switch the light bulb, contact elements K1.2 of relay P1 are used. If the battery is being charged with the main current, the LED lights up yellow, and if the recharging mode is turned on, it turns green. It is possible to use two devices of the same color, but they must be connected correctly.
8. Operational amplifier KR1005UD1. You can take the device from an old video player. The main feature is that this part does not require two polar power supplies; it can operate at a voltage of 5-12 volts. Any similar spare parts can be used. But due to different numbering of pins, it will be necessary to change the design of the printed circuit.
9. Relays P1 and P2 must be designed for voltages of 9-12 volts. And their contacts are designed to operate with a current of 1 ampere. If devices are equipped with several contact groups, it is recommended to solder them in parallel.
10. Relay P3 is 9-12 volts, but the switching current will be 10 amperes.
11. Switching device S1 must be designed to operate at 250 volts. It is important that this element has enough switching contact components. If the adjustment step of 1 ampere is not important, then you can install several switches and set the charge current to 5-8 A.
12. Switch S2 is designed to deactivate the charge level control system.
13. You will also need an electromagnetic head for a current and voltage meter. Any type of device can be used, as long as the total deviation current is 100 µA. If not voltage is measured, but only current, then a ready-made ammeter can be installed in the circuit. It must be rated to operate with a maximum continuous current of 10 amps.

User Artem Kvantov spoke in theory about the circuit of the charging equipment, as well as the preparation of materials and parts for its assembly.

Procedure for connecting the battery to chargers

The instructions for turning on the charger consist of several steps:

1. Cleaning the battery surface.
2. Removing plugs for filling liquid and monitoring the electrolyte level in jars.
3. Setting the current value on the charging equipment.
4. Connecting the terminals to the battery with correct polarity.

Surface cleaning

Guidelines for completing the task:

1. The car's ignition is turned off.
2. The hood of the car opens. Using appropriately sized wrenches, disconnect the clamps from the battery terminals. To do this, you do not need to unscrew the nuts; they can be loosened.
3. The fixing plate that secures the battery is dismantled. This may require a socket or sprocket wrench.
4. The battery is dismantled.
5. Its body is cleaned with a clean rag. Subsequently, the lids of the cans to fill the electrolyte will be unscrewed, so the weight must not be allowed to get inside.
6. A visual diagnosis of the integrity of the battery case is performed. If there are cracks through which electrolyte leaks, it is not advisable to charge the battery.

User Battery Technician talked about cleaning and flushing the battery case before servicing it.

Removing Acid Fill Plugs

If the battery is serviceable, you need to unscrew the caps on the plugs. They can be hidden under a special protective plate; it must be removed. To unscrew the plugs, you can use a screwdriver or any metal plate of the appropriate size. After dismantling, it is necessary to evaluate the electrolyte level; the liquid should completely cover all the cans inside the structure. If it is not enough, then you need to add distilled water.

Setting the charge current value on the charger

The current parameter for recharging the battery is set. If this value is 2-3 times greater than the nominal value, then the charging procedure will occur faster. But this method will lead to a decrease in battery life. Therefore, you can set this current if the battery needs to be recharged quickly.

Connecting the battery with correct polarity

The procedure is performed like this:

1. Clamps from the charger are connected to the battery terminals. First the connection is made to the positive terminal, this is the red wire.
2. The negative cable does not need to be connected if the battery remains in the car and has not been removed. This contact can be connected to the vehicle body or to the cylinder block.
3. The plug from the charging equipment is inserted into the socket. The battery begins to charge. The charging time depends on the degree of discharge of the device and its condition. The use of extension cords is not recommended when performing this task. Such a wire must be grounded. Its value will be sufficient to withstand the current load.

The VseInstrumenti channel talked about the features of connecting a battery to a charger and observing polarity when performing this task.

How to determine the degree of battery discharge

To complete the task you will need a multimeter:

1. The voltage value is measured on a car with the engine turned off. The vehicle's electrical network in this mode will consume part of the energy. The voltage value during measurement should correspond to 12.5-13 volts. The tester leads are connected with correct polarity to the battery contacts.
2. The power unit is started, all electrical equipment must be turned off. The measurement procedure is repeated. The working value should be in the range of 13.5-14 volts. If the value obtained is greater or less, this indicates a discharge of the battery and the operation of the generator device is not in normal mode. An increase in this parameter at low negative air temperatures cannot indicate battery discharge. It is possible that at first the resulting indicator will be higher, but if over time it returns to normal, this indicates efficiency.
3. The main energy consumers are turned on - the heater, radio, optics, rear window heating system. In this mode, the voltage level will be in the range from 12.8 to 13 volts.

The discharge value can be determined in accordance with the data given in the table.

How to calculate the approximate battery charging time

To determine the approximate recharging time, the consumer needs to know the difference between the maximum charge value (12.8 V) and the current voltage. This value is multiplied by 10, resulting in the charging time in hours. If the voltage level before recharging is 11.9 volts, then 12.8-11.9 = 0.8. By multiplying this value by 10, you can determine that the recharging time will be approximately 8 hours. But this is provided that a current of 10% of the battery capacity is supplied.

The article describes a set-top box designed to work together with a charger that does not have the function of disconnecting from the network after charging the battery. This set-top box should be of interest, first of all, to those car enthusiasts who, having a simple factory-made or home-made charger, would like to automate the charging process with minimal time and money.

It is known that the voltage at the terminals of a lead-acid battery charged with a stable current almost stops increasing as soon as it receives a full charge. From this moment on, almost all the energy supplied to the battery is spent only on electrolysis and heating of the electrolyte. Thus, at the moment the increase in charging voltage stops, it would be possible to disconnect the charger from the network. The operating instructions for car batteries recommend, however, that you continue charging in this mode for another two hours. This is exactly how the automatic charger I described earlier works. However, practice shows that this recharging is really only necessary when conducting an annual control and preventative charge-discharge cycle in order to determine the technical condition of the battery.

In everyday use, it is quite enough to keep the battery under constant voltage for 15...30 minutes. This approach makes it possible to significantly simplify the automatic charger without noticeably affecting the completeness of battery charging. If you charge the battery with an unstabilized current, then along with a gradual increase in the charging voltage (less pronounced than in the first case), the charging current decreases. Evidence of a fully charged battery is the cessation of changes in both voltage and current.

This principle forms the basis for the operation of the proposed set-top box. It contains a comparator, one of the inputs of which is supplied with a voltage that increases proportionally as the charging voltage on the battery increases (and decreases as it decreases) and at the same time proportionally decreases as the charging current increases (increases with decrease). The second input is supplied with the same voltage as the first, but with a significant time delay. In other words, as long as the voltage on the battery increases and (or) the charging current decreases, the voltage value at the second input of the comparator will be less than the voltage value at the first, and this difference is proportional to the rate of change of the charging voltage and current. When the voltage on the battery and the charging current stabilize (which will indicate that the battery is fully charged), the voltage values ​​at the inputs of the comparator will be equal, it will switch and give a signal to turn off the charger. This idea is borrowed from.

The attachment is made using widely used elements. The maximum operating current is 6 A, but if necessary it can be easily increased.

The schematic diagram of the attachment is shown in Fig. 1.

The device consists of an input op-amp da1, two voltage comparators on the op-amp da2.1, da2.2, a two-input electronic relay vt1 - vt3, K1 and a power supply consisting of a network transformer T1, diodes vd1-vd4, a smoothing capacitor C6 and a parametric voltage stabilizer vd5r19. The output of the charger is connected to terminals X1, X3, and the battery being charged is connected to terminals X2, X3. The mains plug of the charger is plugged into the X5 socket of the set-top box.

When you press the sb1 button, the mains voltage is supplied to the charger and to the mains winding i of transformer T1 of the set-top box. The unstabilized voltage from the diode bridge vd1-vd4 powers the electronic relay, and the output voltage of the parametric stabilizer powers the da2 chip (da1 is powered by the charger). Battery charging begins.

The voltage drop created by the charging current across resistor r1 is fed to the input of op-amp da1, connected according to the inverting amplifier circuit. The voltage at its output will increase as the charging current decreases. On the other hand, the output voltage of an op-amp is proportional to its supply voltage. And since the amplifier is powered directly from the battery being charged, the output voltage of the op-amp will be a function of both the voltage at the terminals of the battery being charged and the charging current. This design of the console made it possible to use it in conjunction with a wide variety of chargers, including the simplest ones.

A low-pass filter r4c2 is connected to the output of the op-amp, from which the voltage through the integrating circuits r7c3 and r5r6r8c4 is supplied to the inputs of the comparator made on op-amp da2.2. Circuit r8c4 has a time constant many times larger than circuit r7c3, so the voltage at the non-inverting input of this comparator will be less than at the inverting input, and the output will go low.

The op-amp comparator da2.1 is a conventional threshold device, the inverting input of which is supplied with a reference voltage from the resistive divider r15r16, and the non-inverting input is supplied with a reference voltage from the divider r11r12r13, connected to the battery being charged. The comparator switches when the battery voltage reaches 14.4 V and serves to eliminate the possibility of premature shutdown of the charger in conditions of insignificant changes in voltage changes on the battery.

As a result, until the voltage on the battery being charged reaches the specified value, the set-top box will not turn off the charger, even if the da2.2 comparator has switched. This situation is possible when the charging current is set to a low value and, as a consequence, when the charging voltage and current change very slowly. Initially, the output of comparator da2.1 also has a low level voltage.

The outputs of both comparators are connected through resistive dividers r17r18 and r20r21 to the bases of transistors vt2 and vt1. Thus, when you press the sb1 button, these transistors remain closed, and vt3 opens. Relay K1 is activated and contacts K1.1 blocks the button contacts. The set-top box remains on after the button is released.

Since transistors vt1 and vt2 are connected in an AND logic circuit, they open only at a high voltage level simultaneously at the output of comparators da2.1, da2.2. This can only happen when the battery is fully charged. In this case, transistor vt3 closes and relay K1 releases the armature, opening the power circuit of the set-top box and charger.

In Fig. Figure 2 shows graphs of changes in voltage at the inputs of the comparator da2.2, as well as the charging current during the process of recharging the 6ST-60 battery using a simple charger with an unstabilized charging current. The initial state of charge of the battery is about 75%.

In the case when the set-top box will operate in conditions of strong interference, the power supply circuit of the op-amp da2 should be bypassed with a ceramic capacitor with a capacity of 0.1 µF.

The set-top box is characterized by reduced sensitivity to mains voltage fluctuations. If, for example, it increases, then the voltage on the battery being charged also increases, but at the same time the charging current will also increase. As a result, the voltage at the output of op-amp da1 will change slightly.

The attachment is mounted in a metal box measuring 140x100x70 mm. On its front panel there are clamps X1-X3, fuse fu1 and socket X5. Most of the parts of the console are placed on a printed circuit board measuring 76x60 mm, made of foil fiberglass 1.5 mm thick. The board drawing is shown in Fig. 3. Transformer T1 and relay K1 are mounted separately next to the board. Resistor r1 is soldered directly to terminals X1, X2.

Resistor r1 is made up of two parallel-connected resistors C5-16V with a resistance of 0.1 Ohm and a rated dissipation power of 1 W; the rest are constant - MLT. Trimmer resistors r9, r12 - SPZ-16v.

Capacitor C1 - KM5, the rest - K50-35. It is advisable to train capacitor C4 before installing it on the board by connecting it to a constant voltage source of 10...12 V for several hours.

Instead of KD105B, you can use KD106A diodes, and instead of KD522B, you can use any of the KD521 series. Zener diode vd5 - any low-power one with a stabilization voltage of 11... 13 V.

KT3102B transistors are replaceable with any low-power ones of the appropriate structure with a static base current transfer coefficient of at least 50, and when replacing transistor vt3, you should focus on the operating current of the existing relay K1. When choosing a replacement op-amp K553UD2, it is necessary to take into account that not all operational amplifiers allow operation with an input voltage equal to the supply voltage.

The set-top box uses a ready-made low-power network transformer with an alternating voltage of the secondary winding of 14 V at a load current of up to 120 mA. Relay K1 - RMU, passport RS4.523.303, but any one with an operating voltage of 12...14 V, whose contacts are designed for switching an alternating voltage of 220 V at a current of 0.3...0.5 A, is suitable.

To set up the set-top box, you will need a stabilized voltage source, adjustable within 10... 15 V, and a digital voltmeter with a measurement limit of 20 V. First, the resistor slider r12 is set to the bottom, and r9 to the left position according to the diagram. A source is connected to terminals X1 and X3, the voltage at its output is set to 14.4 V and the set-top box is connected to the network.

Press the sb1 button, and relay K1 should operate. Make sure that there is a low voltage level (1.3... 1.5 V) at the op-amp outputs da2.1 and da2.2 (pins 10 and 12). Then measure the voltage at the output of op-amp da1 (pin 10). It should be approximately equal to the voltage of the connected power source.

The terminals of resistor r8 are short-circuited for 30...40 s, ensuring fast charging of capacitor C4, and then after a ten-minute wait, the voltmeter is connected to the output of the op-amp da2.2 and the handle of resistor r9 is smoothly rotated until the comparator switches, i.e., the voltage increases abruptly its output to 11... 11.5 V. Then measure the voltage at the inverting input of the op-amp da2.2 and use resistor r9 to reduce it by 15...20 mV.

It should be noted that the voltage in the input circuits of the comparator must be measured with a digital voltmeter with an input resistance of at least 5...10 MOhm in order to prevent capacitor c3 from discharging. Since the input resistance of many popular digital voltmeters does not exceed 1 MΩ, you can connect a ten-megaohm resistor at the input of the existing voltmeter, which, together with the input resistance of the device, forms a voltage divider with a ratio of 1:10.

Finally, rotate the knob of resistor r12 until the op amp da2.1 switches. In this case, relay K1 should release the armature.

If a radio amateur does not have a digital voltmeter and does not have a power source, the set-top box can be adjusted directly during the actual process of charging the battery. To do this, connect the charger and battery to the set-top box, set the charger switch to the “On” position, and set the resistor sliders r9, r12 of the set-top box as indicated above. Press the sb1 button, make sure that relay K1 is activated and set the charging current in accordance with the operating instructions for the charger.

When the voltage stops increasing, continue charging in this mode for another 20...30 minutes and then smoothly rotate the resistor knob r9 until op-amp da2.2 is activated and the set-top box and charger are disconnected from the network. This concludes the adjustment.

In conclusion, it should be noted that to ensure that the battery is fully charged, it is advisable to set the maximum permissible values ​​of the charging current in order to ensure good dynamics of the voltage change at the output of op-amp da1. This is especially true for chargers with unstabilized output current and heavily discharged batteries.

Literature

• ZHUITs.563.410.001IE. Rechargeable lead starter batteries with a capacity of over 30 Ah. User manual. 1987.
• Kupriyanov K. Automatic charger. - Radio, 2000, No. 12, p. 33-37.
• Tenev L. Device for detecting moving metal objects. - Radio, 1987, No. 5, p. 61.

For those who don’t have time to “bother” with all the nuances of charging a car battery, monitoring the charging current, turning it off in time so as not to overcharge, etc., we can recommend a simple car battery charging scheme with automatic shutdown when the battery is fully charged. This circuit uses one low-power transistor to determine the voltage on the battery.

Scheme of a simple automatic car battery charger

List of required parts:

• R1 = 4.7 kOhm;
• P1 = 10K trimmer;
• T1 = BC547B, KT815, KT817;
• Relay = 12V, 400 Ohm, (can be automotive, for example: 90.3747);
• TR1 = secondary winding voltage 13.5-14.5 V, current 1/10 of the battery capacity (for example: battery 60A/h - current 6A);
• Diode bridge D1-D4 = for a current equal to the rated current of the transformer = at least 6A (for example D242, KD213, KD2997, KD2999...), installed on the radiator;
• Diodes D1 (in parallel with the relay), D5.6 = 1N4007, KD105, KD522...;
• C1 = 100uF/25V.
• R2, R3 - 3 kOhm
• HL1 - AL307G
• HL2 - AL307B

The circuit lacks a charging indicator, current control (ammeter) and charging current limitation. If desired, you can put an ammeter at the output at the break of any of the wires. LEDs (HL1 and HL2) with limiting resistances (R2 and R3 - 1 kOhm) or light bulbs in parallel with C1 “mains”, and to the free contact RL1 “end of charge”.

Changed scheme

A current equal to 1/10 of the battery capacity is selected by the number of turns of the secondary winding of the transformer. When winding the transformer secondary, it is necessary to make several taps to select the optimal charging current option.

The charge of a car (12-volt) battery is considered complete when the voltage at its terminals reaches 14.4 volts.

The shutdown threshold (14.4 volts) is set by trimming resistor P1 when the battery is connected and fully charged.

When charging a discharged battery, the voltage on it will be about 13V; during charging, the current will drop and the voltage will increase. When the voltage on the battery reaches 14.4 volts, transistor T1 turns off relay RL1, the charging circuit will be broken and the battery will be disconnected from the charging voltage from diodes D1-4.

When the voltage drops to 11.4 volts, charging resumes again; this hysteresis is provided by diodes D5-6 in the emitter of the transistor. The circuit's response threshold becomes 10 + 1.4 = 11.4 volts, which can be considered to automatically restart the charging process.

This homemade simple automatic car charger will help you control the charging process, not track the end of charging and not overcharge your battery!

Website materials used: homemade-circuits.com

Another version of the charger circuit for a 12-volt car battery with automatic shutdown at the end of charging

The scheme is a little more complicated than the previous one, but with clearer operation.

Table of voltages and percentage of battery discharge not connected to the charger

P O P U L A R N O E:

In recent years, electronic devices are increasingly used in automobile transport, including electronic ignition devices. The progress of automobile carburetor engines is inextricably linked with their further improvement. In addition, new requirements are now being imposed on ignition devices aimed at radically increasing reliability, ensuring fuel efficiency and environmental friendliness of the engine.

Do-it-yourself powerful laboratory power supply with a MOSFET transistor at the output

In the previous article we looked at