A simple charger for car batteries. Scheme, description

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A simple charger for car batteries. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Automobile. Batteries, chargers

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The diagram of the device is shown in the figure. Setting the required charging current from 0 to 10 A is carried out in a known way: by changing the opening delay of the regulatory element - the trinistor - after the passage of the alternating supply voltage through zero. After connecting the XP1 plug to the network and closing the SA1 switch, the voltage of 220 V, 50 Hz through the FU1 fusible link is supplied to the primary winding of the step-down transformer T1. Capacitor C1 - noise suppression. Neon lamp HL1 - indicator of the presence of mains voltage.

Simple car battery charger
Fig. 1

The voltage from the secondary winding, composed of six sections connected in series, is supplied to the diode bridge VD1-VD4 and diodes VD5, VD6. The voltage rectified by the diode bridge through the RA1 ammeter and the FU2 fusible insert is supplied to the positive terminal of the rechargeable battery, and through the control element - the VS1 trinistor to the negative terminal. The rectified voltage from the cathodes of the diodes VD5, VD6 and the negative terminal of the VD1-VD4 bridge is supplied to the voltage limiter, and through the resistor R2 to the HL2 LED. The glow of the latter indicates the presence of voltage on the secondary winding of the transformer T1. The limiter is assembled on a VD7 zener diode and a resistor R3. From its output, a voltage close to a trapezoidal shape (half-sine wave with truncated peaks) and a frequency of 100 Hz is fed to the VS1 trinistor control unit. It is a pulse generator on a unijunction transistor VT1. Variable resistor R4, resistor R5 and capacitor C2 are the timing circuit of the generator.

With the beginning of each trapezoidal pulse, formed, as indicated above, by the zener diode VD7 and resistor R3, the charging of capacitor C2 begins through resistors R4, R5. Unijunction transistor VT1 is closed. When the capacitor C2 reaches the turn-on voltage of the transistor, the capacitor C2 is discharged through the circuit emitter-base section 1 of the transistor, resistor R6. The pulse on the resistor R6 opens the trinistor VS1, and the voltage from the diode bridge VD1-VD4 is supplied to the battery being charged. The duration of this voltage supply is the difference between the duration of the half-cycle of the mains voltage (10 ms) and the turn-on delay of the trinistor from the beginning of the half-cycle (the passage of the mains voltage through zero). When moving the slider of the variable resistor R4 to the left according to the scheme, the trinistor will open closer to the end of each trapezoidal pulse arriving at the control unit, and the charging current will be less. On the contrary, when the resistor slider is moved to the right, the charging current will increase.

Structurally, the device can be placed both in a home-made case and in a finished one, for example, from some device that has served its time. Cases from devices B3-38 - VZ-41, VZ-47, VZ-57 are very well suited, which are easy to modify by replacing the front panel and drilling the required number of ventilation holes to ensure cooling of the device.

Fusible insert FU1 - VP1-1 5A, 250 V. An insert for a lower current is not recommended, since it will systematically burn out when the device is turned on. Insert FU2 - VPZB-1 for 10 A. Switch SA1 type ТЗ can be replaced by a key switch with light indication, for example, R59-2 [1], while the elements R1 and HL1 are excluded. Capacitor C1 - K73-17 for a voltage of 630 V. Its capacitance can be in the range of 0,01 ... 0,22 microfarads. This capacitor is soldered directly to terminals 1 and 6 of the transformer T1. Capacitor C2 - any for a voltage of at least 25 V.

Transformer T1 - unified TPP320-127 / 220-50 [2] with a power of 200 watts. It can be replaced by TPP318-127 / 220-50 or TPP310-127 / 220-50, the winding switching circuit is identical.

It is possible to use the TPP323-127 / 220-50 transformer, while the windings with terminals 11-12, 13-14, 18-17, 20-19 must be connected in parallel, i.e. solder together terminals 11, 13, 18, 20 and 12, 14, 17,19.

The secondary windings of this transformer can be connected in another way by making the rectifier according to the usual full-wave circuit. In this case, instead of the diode bridge VD1-VD4, only two diodes are installed. Windings with pins 11-12, 13-14 should be connected in parallel, windings with pins 18-17, 20-19 should also be connected in parallel, that is, pins 11,13 should be together; 12, 14; 17, 19 and 18, 20, and then connect pin 14 to pin 18 - this will be the midpoint and negative terminal of the rectifier. The extreme conclusions 11, 13 and 19, 17 are soldered to the anodes of powerful rectifier diodes.

You can also use a network transformer from an old color tube TV. First you need to remove all its secondary windings, while counting the number of turns of the on-line winding. Further, on each of the two frames, a new secondary winding is wound with a wire with a cross section of at least 3 mm2 in any heat-resistant insulation with the number of turns three times more than the incandescent one. After assembling the transformer, the coils are connected in series. In the absence of a wire of the required cross section, a bundle of thinner wires can be used, weaving them into a pigtail [3]. Before installing a homemade transformer, it is necessary to check the insulation resistance between the primary and secondary windings - it must be at least 20 MΩ. Otherwise, dry the transformer in a warm, dry place and measure the insulation resistance again, and if it is again less than 20 MΩ, then it is better not to use such a transformer.

Diodes D214 can be replaced by any with a forward current of at least 10 A and a reverse voltage of at least 100 V. They are installed on heat sinks with a surface area of at least 50 cm2. Diodes VD5, VD6 - any low-power silicon. We can replace the trinistor with any of the KU202 series or more powerful, for example, from the T122 series (T122-20, etc.) [4]. It is installed on a heat sink with an area of at least 100 cm2. We will replace the KT117A transistor with KT117B, KT117G; CT132A, CT132B; KT133A, KT133B or imported 2N2646, 2N2647, 2N4870, 2N4871. Instead of a unijunction transistor, you can use its transistor counterpart. Ammeter RA1 and voltmeter PV1 - M4202, M4203. Fixed resistors - any type. Variable resistor R4 with a linear characteristic. Its resistance can be from 100 to 680 kOhm. In this case, it will be necessary to select the capacitance of the capacitor C2 so that the time constant R4C2 remains the same. The resistor leads must be connected so that when the knob is rotated clockwise, the introduced resistance decreases.

The printed circuit board was not developed. A properly assembled device does not require adjustment. However, before switching on for the first time, instead of the FU1 fusible insert, connect a 220 V incandescent lamp with a power of 100 ... 150 W. When SA1 is turned on, the lamp should flash and go out. If it burns almost to full heat, you should check the correct connection of the transformer windings, the presence of short circuits in the secondary circuit. Further, turning the knob of the variable resistor to the extreme counterclockwise (initial) position, a 1 V car lamp with a power of 12 W is connected in parallel to the voltmeter PV15. It shouldn't glow. By smoothly turning the knob of the variable resistor clockwise, you should make sure that the lamp lights up and its brightness increases to full when the voltmeter reads about 15 V. It may be necessary to adjust the capacitance of capacitor C2. When operating the device, before connecting the load, the handle of the variable resistor R4 should always be set to its initial position.

Literature

Yushin A. Key switches with light indication. - Radio, 2005, No. 5, p. 52.
unified transformers. - Radio, 1982, No. 1, p. 59, 60.
Kobelev F. G. How to make welding machines with your own hands. - S.-Pb.: Science and technology, 2011, p. 156.
Thyristors (Technical reference). Per. from English, ed. Labuntsova V. A., Obukhova S. G., Sviridova A. F. Izd. 2nd, add. - M.: Energy, 1971, p. 111 - 118.

Authors: A. Kvakina, P. Mikheev

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