This circuit is an alternative to expensive battery chargers, the trick to lower the cost is to buy a cheap battery charger and expand it with an automatic charge breaker circuit such as the one presented here.
The heart of this automatic battery charger is the comparator which compares the NiCad battery’s voltage with a referance voltage. When the NiCad battery’s voltage exceeds a certain presettable maximum voltage level, the circuit breaks the charging via the relay and when the NiCad battery’s voltage sinks below the preset minimum level, the circuit closes the relay and the charging resumes. continue reading…

The universal battery charger’s output voltage is adjustable and regulated, and has an ajustable constant-current charging circut that makes it easy to use to use with most NiCad batteries. The charger can charge a single cell or a number of series-connected cells up to a maximum of 18V. continue reading…

There are two main types of battery charger – constant voltage and constant current. Both have their advantages and disavantages. For constant voltage, the battery cannot be overcharged but the charging rate is slow. Constant current mode can charge batteries more swiftly but there is the danger of overcharging them.
The dual mode battery charger circuit featured here was designed to combine both modes, but without their disadvantages, for use with a 6V sealed lead-acid battery. The main players of the circuit are voltage regulator IC1, which is used for constant current mode, and precision adjustable shunt regulator IC2, which is used for constant voltage mode. continue reading…