One very simple but reliable ac mains powered battery charger circuit for the handy pen torch is also included here. Basically the pen torch circuit is a constant current charger wired around ...

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 ...

Instead, battery charging is broken down into two distinct phases — constant current and constant voltage. The diagram below shows how voltage changes during charging and how that impacts the ...

This circuit makes a great constant-current charger with selectable voltage cutoff. The minimalism is largely gone, using three transistors now. And it still lacks Ralph’s charging-done LED.