Charger for 12-volt batteries, 4,5 Ah. Scheme, description

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Charger for 12-volt batteries, 4,5 Ah. 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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If the battery output voltage drops below 11,5 Volts (this parameter can be configured), then the device starts charging it. When the battery output voltage rises to 12,5 Volts (this parameter can be configured), the device will automatically stop charging.

For the operation of the device, a constant voltage of 15 Volts (not stabilized, can be taken from a diode bridge), with a power of 0,5 A. And a constant voltage of 13 Volts, with a power of 2 A (depending on the technical characteristics of the battery) is required.

(click to enlarge)

The device consists of comparators assembled on K140UD12 operational amplifiers. Timer assembled on DD1,DD2,DD3 chips and match node on DD4,DD5 chips.

When the device is turned on, it measures the voltage on the battery and compares it with the threshold (for example, 11,5 V) if the voltage at the battery output is less than the threshold, then the device starts charging the battery (while the voltage at the battery output is not measured), after 7 minutes of charging, the device stops charging battery and check its voltage. If the battery output voltage is less than 12,5 Volts, then the device starts charging the battery again. And so on until the voltage at the battery output becomes higher than 12,5 volts.

For convenience in setting up the device, I built in control points there (X1, X2, X3, X4). At point X3 there should be +15 Volts. At point X4 there should be a voltage of +5 Volts, it can be adjusted using a variable resistor R19. The voltage at point X1 is the threshold for turning off battery charging. It can be adjusted using a variable resistor R2 (I set the voltage to 12,5 volts there). The voltage at point X2 is the threshold for starting battery charging. It can be adjusted using a variable resistor R10 (I set a voltage of 11,5 volts there). To adjust the thresholds for the device, you can use a low-power PSU with an adjustable output voltage of 10-14 volts. You need to put a diode on its output and connect it instead of the battery.

The device uses microcircuits from the K155 series and operational amplifiers K140UD12. The RES22 relay, transistors from the KT315 and KT815 series are used. Resistors and diodes - any low-power.

Author: Giorgi Gulabyan; Publication: cxem.net

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