Here's a link to a useful .pdf document from National Semiconductor detailing the differences in charging requirements for NiCd, NiMH and Li-Ion cell types and giving some example circuits for chargers (using their ICs of course). 
http://goo.gl/scTIG

http://goo.gl/scTIG
--
Ian
100,000 lemmings can't be wrong!
Ian
100,000 lemmings can't be wrong!







