During the last years many new types of recargeable Batteries were developed, NIMh, LIIOn, NICd, Lead Gel Cells to name just a few. For every application a suitable type of Battetry can be found. Each type needs to be charged with an appropriate method, like constant Current, Constant Voltage and many more.
Here you may find Circuit, Basics, Schematic Diagram and DIY Kit components for Battery Charger