.... one of the rumored/reported benefits of regen braking: being able to give a 100+ Amp burst into the pack, keeping Hawkers alive, besides the usual recharging at a low rate till full....
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of EVDL Administrator Sent: Wednesday, January 30, 2013 4:26 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Another Delta-Q question On 30 Jan 2013 at 21:46, Roger Stockton wrote: > The issue with not providing the batteries with the required charge > current is that Enersys/Odyssey believes they will not end up fully > charged. I hadn't heard that undercharging was the root of the problem, but I did indeed hear many years ago that (then) Hawker Genesis batteries needed at least an initial "sock" of high charging current, or they'd have significant capacity loss and short cycle lives. > Anecdotal reports on this list in the past suggest that those who have > ignored the recommendation have indeed experienced shorter battery life > than expected, and I believe, warranty denial. That was Solectria's experience in the 1990s, when they used Hawkers for a while. Massachusetts DOER's program was in the thick of this. Their report from 1999 outlines the symptoms, though I'm not sure that I agree with all of their diagnosis. "... certain battery types are dependent on high-powered (Level II 208-240v) charging systems. In particular, lead-acid batteries manufactured by Hawker- Genesis developed a memory problem if short-cycled or deprived of the opportunity to equalize as a "pack" (a 12-14 hour process when charged at 120v). If only used or charged for a short period of time, the batteries "remembered" that as the maximum amount of charge or energy available and [would not] produce energy beyond that level. "After a year or less of service, batteries that originally had a 57 ampere hour rating (at a constant 30 amp discharge rate), were only producing 25 ampere hours -- the equivalent of about 20 miles. Further, the manufacturer of the Hawker-Genesis replacement batteries failed to honor the warranty when the (replacement) batteries experienced significant energy degradation after as little as three months use." > It isn't completely cut and dried, since at least some of these > instances have involved parallel strings, which causes additional > challenges for charging. Solectria was using two parallel strings of Hawkers in Forces. Their early 1kW chargers were woefully underpowered for them. I'm not so sure that the even their later 3kW 240v chargers really hit the batteries hard enough. Solectria's solution was to dump the Hawkers (they even offered their stock at a cut-rate price here on the EVDL) and switch to gel batteries - Sonnenschein, and later East Penn Deka Dominator, which reportedly licensed the Sonnenschein design - for their lead-acid cars. They used these gel batteries right up to the very end of the Force range, with consistently good cycle life. David Roden EVDL Administrator http://www.evdl.org/ _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
