Charger with manual and automatic operation. Scheme, description

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Charger with manual and automatic operation. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The device, when the battery is stored in winter, allows you to automatically turn it on for charging when the voltage drops and also automatically turn off charging when the voltage corresponding to a fully charged battery is reached.

The charger circuit provides two modes of operation - manual and automatic.

In manual mode, the SA1 toggle switch is on. After switching on the toggle switch Q1, the mains voltage is supplied to the primary winding of the transformer T1 and the indicator light HL1 lights up. The SA2 switch sets the required charging current, which is controlled by the PA1 ammeter. The voltage is controlled by a voltmeter PU1. The operation of the automation circuit does not affect the charging process in manual mode.

Charger with manual and automatic operation. Charger circuit

In automatic mode, the SA1 toggle switch is open. If the battery voltage is less than 14,5 V, the voltage at the terminals of the zener diode VD5 is less than necessary to unlock it, and the transistors VT1, VT2 are locked. Relay K1 is de-energized and its contacts K1.1 and K1.2 are closed. The primary winding of the transformer T1 is connected to the network through the contacts of the relay K1.1. Relay contacts K1.2 close the variable resistor R3. The battery is being charged. When the voltage on the battery reaches 14,5 V, the Zener diode VD5 begins to conduct current, which leads to the unlocking of the transistor VT1, and consequently, the transistor VT2. The relay is activated and contacts K1.1 turns off the power to the rectifier.

Due to the opening of contacts K1.2, an additional resistor R3 is included in the voltage divider circuit. This leads to an increase in the voltage on the zener diode, which now remains in a conducting state even after the voltage on the battery is less than 14,5 V. The battery stops charging and a storage mode begins, during which a slow self-discharge occurs. In this mode, the automation circuit is powered by the battery. The zener diode VD5 will stop passing current only after the battery voltage drops to 12,9 V. Then the transistors VT1 and VT2 will turn on again, the relay will de-energize and the contacts K1.1 will turn on the power to the rectifier. The battery will start charging again. Contacts K1.2 will also close, the voltage on the zener diode will further decrease, and it will start to pass current only after the voltage on the battery increases to 14,5 V, that is, when the battery is fully charged.

The charger automation unit is configured as follows. The XP1 connector is not connected to the network. Instead of a battery, a stabilized DC source with an adjustable output voltage, which is set by a voltmeter equal to 2 V, is connected to the XP14,5 connector. In this case, the transistors must be locked, and the relay is de-energized.

Slowly rotating the axis of the variable resistor R4, you need to achieve relay operation. Then, a voltage of 2 V is set at the terminals of the X12,9 connector, and by slowly rotating the axis of the variable resistor R3, the relay must be released. Due to the fact that when the relay is released, the resistor R3 is closed by contacts K1.2, these adjustments are independent of one another. The resistances of the voltage divider resistors R2-R5 are calculated in such a way that the operation and release of the relay should occur, respectively, at voltages of 14,5 and 12,9 V in the middle positions of the variable resistors R3 and R4. If other values of the actuation and release voltages of the relay are needed, and the adjustment limits of the variable resistors are not enough, you will have to select the resistances of the constant resistors R2 and R5.

Relay - any type with two groups of opening or switching contacts, reliably operating at a voltage of 12 V. You can, for example, use the RSM-3 relay passport RF4.500.035P1 or RES6 passport RFO.452.125D.

Author: V. Fomin; Publication: cxem.net

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a guest
It follows from the above diagram that the battery in the "storage" mode, in addition to self-discharge, has an additional "assistant" in the form of an on relay, which is not good. At the very least, something can be done about this by supplementing the relay power circuit with a lower voltage, but this is also not the best way out. It would be better to invert the cascade so that the relay turns on when charging, something like this [;)]

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