Automatic battery charger
The following automatic battery-charger design is created with a circuit that could qualify as the simplest window comparator ever built around a single transistor. It starts charging when the battery voltage drops beyond a preset value, and it stops when an upper preset voltage is attained. With the help of a precise variable voltage supply, the upper and lower voltage levels were set. The normally connected (NC) lead of the relay isn’t joined to the 15-V dc supply, which blocks this voltage from passing to the battery leads. This will accurately set the upper and lower levels. But the charging supply of 15 V dc was connected to the circuit.

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Automatic battery charger
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