Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!mit-eddie!bloom-beacon!tut.cis.ohio-state.edu!cs.utexas.edu!sm.unisys.com!sdcsmb!poi!darrelj From: darrelj@sm.unisys.com (Darrel VanBuer) Newsgroups: comp.sys.ibm.pc Subject: Re: Overcharging NiCad batteries? Keywords: NiCad rechargeable batteries, laptops Message-ID:Date: 26 Sep 88 15:29:41 GMT References: <3008@dalcs.UUCP> <14705@agate.BERKELEY.EDU> Reply-To: darrelj@sm.unisys.com (Darrel VanBuer) Distribution: na Organization: Unisys Santa Monica Lines: 12 I use NiCds as a ham, but characteristics are general. On charging: once the battery is fully charged, the extra current goes into heating up the battery and disassociating water into hydrogen and oxygen. Both of these are hard on the battery. On discharging: NiCds eventually "learn" how you use them. If you use 25% and recharge regularly, they eventually will give out after 25% use. While its not necessary to go all the way down every time, you should do so regularly. BUT don't over discharge either, because if you go beyond the capacity of the weakest cell in the battery, it gets run in reverse which causes whiskers of metal to grow and eventually short out the cell. Also with a partial discharge, its hard to guess how long to charge without overcharging.