Parameters d242 are suitable for the charger. Overview of car battery charger circuits

Compliance with the operating mode of batteries, and in particular the charging mode, guarantees their trouble-free operation throughout the entire service life. The batteries are charged with a current, the value of which can be determined by the formula

where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.

A classic car battery charger consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats are used as current regulators (see Fig. 1) and transistor current stabilizers.

In both cases, significant thermal power is released on these elements, which reduces the efficiency of the charger and increases the likelihood of its failure.

To adjust the charging current, you can use a store of capacitors that are connected in series with the primary (mains) winding of the transformer and act as reactances that dampen excess mains voltage. A simplified version of such a device is shown in Fig. 2.

In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is negligible.

The disadvantage in Fig. 2 is the need to ensure the voltage on the secondary winding of the transformer is one and a half times greater than the rated load voltage (~ 18÷20V).

The charger circuit that provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.

It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.

With switches Q1 - Q4, you can connect various combinations of capacitors and thereby regulate the charging current.

The variable resistor R4 sets the threshold K2, which should be triggered when the voltage at the battery terminals is equal to the voltage of a fully charged battery.

On Fig. 4 shows another charger, in which the charging current is continuously adjustable from zero to the maximum value.

The change in the current in the load is achieved by adjusting the opening angle of the trinistor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5 slider. The maximum battery charge current is 10A, set by an ammeter. The device is provided on the mains and load side by fuses F1 and F2.

A variant of the printed circuit board of the charger (see Fig. 4), 60x75 mm in size, is shown in the following figure:

In the diagram in fig. 4 the secondary winding of the transformer must be designed for a current three times the charging current, and accordingly the power of the transformer must also be three times the power consumed by the battery.

This circumstance is a significant drawback of chargers with a current regulator trinistor (thyristor).

Note:

Rectifier bridge diodes VD1-VD4 and thyristor VS1 must be installed on radiators.

It is possible to significantly reduce power losses in the trinistor, and therefore increase the efficiency of the charger, by transferring the control element from the secondary winding circuit of the transformer to the primary winding circuit. such a device is shown in Fig. 5.

In the diagram in Fig. 5, the control unit is similar to that used in the previous version of the device. The trinistor VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is about 10 times less than the charge current, a relatively small thermal power is released on the VD1-VD4 diodes and the VS1 trinistor and they do not require installation on radiators. In addition, the use of a trinistor in the primary circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the shape factor of the current curve (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing the design (for example, use a variable resistor with a plastic axis).

A variant of the printed circuit board of the charger in Figure 5, 60x75 mm in size, is shown in the figure below:

Note:

Rectifier bridge diodes VD5-VD8 must be installed on radiators.

In the charger in Figure 5, the diode bridge VD1-VD4 of the type KTs402 or KTs405 with the letters A, B, C. The zener diode VD3 of the type KS518, KS522, KS524, or composed of two identical zener diodes with a total stabilization voltage of 16 ÷ 24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is single-junction, type KT117A, B, C, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247 and others). Diodes are installed on radiators with an area of ​​​​at least 200 sq.cm, and the radiators will get very hot, you can install a fan for blowing into the charger case.

I made this charger for charging car batteries, the output voltage is 14.5 volts, the maximum charge current is 6 A. But it can also charge other batteries, such as lithium-ion, since the output voltage and output current can be adjusted over a wide range. The main components of the charger were purchased from the Aliexpress website.

These are the components:

You will also need an electrolytic capacitor 2200 uF at 50 V, a transformer for the TS-180-2 charger (look at how to unsolder the TS-180-2 transformer), wires, a power plug, fuses, a radiator for a diode bridge, crocodiles. You can use another transformer with a power of at least 150 W (for a charging current of 6 A), the secondary winding must be rated for a current of 10 A and produce a voltage of 15 - 20 volts. The diode bridge can be assembled from individual diodes rated for a current of at least 10A, for example, D242A.

The wires in the charger should be thick and short. The diode bridge must be fixed to a large radiator. It is necessary to increase the radiators of the DC-DC converter, or use a fan for cooling.

Charger Assembly

Connect the cord with a power plug and a fuse to the primary winding of the transformer TC-180-2, install the diode bridge on the radiator, connect the diode bridge and the secondary winding of the transformer. Solder the capacitor to the positive and negative terminals of the diode bridge.

Connect the transformer to a 220 volt network and measure the voltage with a multimeter. I got these results:

1. The alternating voltage at the terminals of the secondary winding is 14.3 volts (mains voltage is 228 volts).
2. DC voltage after diode bridge and capacitor 18.4 volts (no load).

Based on the diagram, connect a step-down converter and a voltammeter to the DC-DC diode bridge.

Setting the output voltage and charging current

Two trimming resistors are installed on the DC-DC converter board, one allows you to set the maximum output voltage, the other can set the maximum charging current.

Plug the charger into the mains (nothing is connected to the output wires), the indicator will show the voltage at the output of the device, and the current is zero. Set the voltage potentiometer to 5 volts at the output. Close the output wires between each other, set the short circuit current to 6 A with the current potentiometer. Then eliminate the short circuit by disconnecting the output wires and the voltage potentiometer, set the output to 14.5 volts.

This charger is not afraid of a short circuit at the output, but it can fail if the polarity is reversed. To protect against polarity reversal, a powerful Schottky diode can be installed in the gap of the positive wire going to the battery. Such diodes have a low voltage drop when connected directly. With such protection, if you reverse the polarity when connecting the battery, no current will flow. True, this diode will need to be installed on the radiator, since a large current will flow through it when charging.

Suitable diode assemblies are used in computer power supplies. In such an assembly there are two Schottky diodes with a common cathode, they will need to be paralleled. Diodes with a current of at least 15 A are suitable for our charger.

It should be borne in mind that in such assemblies the cathode is connected to the case, so these diodes must be installed on the radiator through an insulating gasket.

It is necessary to adjust the upper voltage limit again, taking into account the voltage drop across the protection diodes. To do this, the voltage potentiometer on the DC-DC converter board must be set to 14.5 volts measured with a multimeter directly at the output terminals of the charger.

How to charge the battery

Wipe the battery with a rag soaked in a solution of soda, then dry. Unscrew the plugs and check the electrolyte level, if necessary, add distilled water. Plugs must be turned out during charging. Debris and dirt must not get inside the battery. The room in which the battery is charged must be well ventilated.

Connect the battery to the charger and plug the device into the mains. During charging, the voltage will gradually increase to 14.5 volts, the current will decrease over time. The battery can be conditionally considered charged when the charging current drops to 0.6 - 0.7 A.

Scheme of the desulfating charger devices proposed by Samundzhi and L. Simeonov. The charger is made on the basis of a half-wave rectifier on diode VI with parametric voltage stabilization (V2) and a current amplifier (V3, V4). Signal lamp H1 lights up when the transformer is connected to the network. The average charging current of approximately 1.8 A is regulated by the selection of resistor R3. The discharge current is set by the resistor R1. The voltage on the secondary winding of the transformer is 21 V (amplitude importance 28 V). The voltage on the battery at the rated charging current is 14 V. Therefore, the charging current of the battery occurs only when the amplitude of the output voltage of the current amplifier exceeds the battery voltage. Description of the microcircuit 0401 During the time of one period of alternating voltage, one pulse is formed charger then during the time Ti. The battery discharge occurs during the time Tz= 2Ti. Therefore, the ammeter shows the average importance charger current, equal to approximately one third of the amplitude value of the total charger and discharge currents. In the charger, you can use the TC-200 transformer from the TV. The secondary windings from both coils of the transformer are removed and a new winding is wound with a PEV-2 1.5 mm wire, consisting of 74 turns (37 turns on each coil). Transistor V4 is mounted on a heatsink with an effective surface area of ​​approximately 200 cm2. Details: Diodes Type VI D242A. D243A, D245A. D305, V2 one or two zener diodes connected in series D814A, V5 type D226: transistors V3 type KT803A, V4 type KT803A or KT808A. When setting up ...

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Scheme of a simple car battery charger

In old TVs that still worked on lamps and not on microchips, there are power transformers TS-180-2

The article shows how to make a simple transformer out of such a transformer. DIY battery charger

Reading

Device Diagram:

At TS-180-2 there are two secondary windings, designed for a voltage of 6.4 V and a current of 4.7 A, if they are connected in series, we will get an output voltage of 12.8 V. This voltage is enough to charge the battery. On the transformer, you need to connect pins 9 and 9 with a thick wire, and to pins 10 and 10, also solder a diode bridge with thick wires, consisting of four diodes D242A or others rated for a current of at least 10 A.

Diodes need to be installed on large radiators. The design of the diode bridge can be assembled on a fiberglass plate of a suitable size. The primary windings of the transformer must also be connected in series, a jumper must be placed between terminals 1 and 1 stroke, and a cord with a plug for a 220 V network must be soldered to terminals 2 and 2. secondary 10 A.

The wires that you use in the manufacture of the charger must be at least 2.5 mm2 in section. Radiator area for a diode, not less than 32 cm2 (for each). In our case, the secondary windings are designed for a current of 4.7 A, so you can't so that the charging current exceeds this value for a long time. The voltage at the battery terminals during charging should not exceed 14.5 V, especially if a maintenance-free battery is being charged.

In our device, the charging current is limited due to the small output voltage of the transformer (12.8 V), but the output voltage depends on the input voltage. If your network voltage is more than 220 V, then, accordingly, the output of the transformer will be more than 12.8 V.

You can limit the charging current by turning on a 12-volt lamp with a power of 21 to 60 watts in series with the battery in the gap of the negative wire. The lower the lamp power, the lower the charging current will be. To control the current and voltage, you need to connect an ammeter with a measurement limit of at least 10 A, and a voltmeter with a measurement limit of at least 15 V to the charger. Or you can buy a multimeter with a current measurement limit of at least 10 A and periodically monitor the parameters with it.

Connect the battery carefully. It is not allowed even for a short time to confuse the plus with the minus when connecting the battery. Also, it is impossible to check the operability of the device by short-term short circuit of the outputs (“check for a spark”). The charger must be de-energized when connecting or disconnecting the battery. When making and using the charger, be careful, follow the rules of fire and electrical safety. Do not leave a running device unattended.

See the diagram of another charger for