In article <[email protected] m>, Chris Maxwell <[email protected]> writes
> I have run a quick test this morning; and I think that Don?s > educated guess is right. I was just about to respond with the same explanation when I saw Don's message. >I still have the pack that I discharged > yesterday; and I haven?t charged it yet. I peeled off the plastic > ?blister packing? and put > it under load just long enough to measure > the voltage on individual cells. Cell #1 was about .5V and diving, > Cell #2 was 1.26, Cell #3 was about .3 and diving, Cell #4 was > 1.26. So, it appears that I have two ?duds? in this pack. At this stage, yes, but read on. > > > > Here is the kicker&I bought these packs new and they have never > seen a charge rate higher than C/6&even that was just momentary > during testing. This pack has been through two charge/discharge > cycles and > both charge cycles were conducted by C/10 slow charging. > The problem is definitely not fast charging. No, but you need to do more cycles.*Usually* three is enough, but some cells need more 'waking up'. If they are no good after five cycles, they are probably done for. > > > > My top three suspects are: > > > > 1. Slow charging too long? I let the pack charge at C/10 over the > weekend in order to really equalize the > cells. The pack never > really heated up (I measured about a 6deg C temp rise). But > maybe NiMH doesn?t like this kind of treatment. I know that > Lead acid and NiCds love it. That shouldn't cause a problem if there was little heat. > > > > 1. Damage from initial discharge cycle? Maybe I let this pack > discharge too deeply during the first discharge test and damaged > the cells. Reverse-charging the two duds may indeed have killed them. > > > > 1. Maybe I just got a dud pack? After all, I just bought them from > some ?batteries-r-us? website. > That's possible too. In summary, I think explanation 1 is probably correct. (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
