In recent years, the battery technology achieved a tremendous progress, inspired by the many new mobile appliances. Were there earlier in essence only lead and NiCad batteries, so you have to do these days with a much larger number of technologies.
Lithium Ion, Lithium Polymer, NiMh to name a few. All require special chargers that are on the physical characteristics of the battery types matched,
Here are some links to Lithium Ion (Lion) Chargers

Here you will find Schematic Circuit Diagram for DIY and further information on Lion battery charger
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Universal Chip for Lion, LiPo, NiMh

ww1.microchip.com/downloads/en/AppNotes/01012a.pdf