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…

This NiCad baterry charger regulator circuit can charge 6 volts as well as 12 volts NiCd batteries. It uses a transformer which can deliver 4 to 5 A current between 12.6 and 15 V. Ordinary chargers select the charging voltage through a swith but the circuit featured here uses an automatic current regulator.

The charging current is automatically regulated to 4.2 amperes. Once the charging current reaches 4A, the voltage drop at R1 will be 600 mV. In this case the transistor T1 will conduct and supplies current to T2. continue reading…

The portable battery charger, car adapter and charger has been designed to provide an opportunity to load NiCd batteries even in the outdoors from a 12 V battery of a vehicle. When the circuit is connected to the vehicle battery, D2 lights only if NiCd battery was connected with the correct polarity. Since even on the discarded batteries we have a certain tension, T1 opens and D2 flashes. continue reading…