Michael, I would think the voltage just before the end of charging would be most crucial. How high do they actually get? That said it sounds like you're at least a little concerned about cooking some of them. You might want to consider adding Lee Hart's light bulb battery balancers.
Peter Flipsen Jr On Feb 2, 2014 11:39 AM, "Michael K Johnson" <[email protected]> wrote: > I am powering my 48V lawn tractor conversion with four Deka Intimidator > 9A31 AGM batteries. I'm using the Soneil SON4812SR 4-stage constant-current > 6A 48V charger. It finished the bulk charge at 6A constant current, and > started the float stage which is constant voltage, and it has ramped the > current down to 0.5A at this point. > > When I measure the voltages across the individual batteries while charging, > I consistently (across three measurements) get 13.56, 13.93, 13.76, and > 13.57 volts. At rest, momentarily after taking them off charge, I get > 13.32, 13.33, 13.35, and 13.36 volts respectively. (I know that's not a > true rest state, so I'm not trying to use that to measure SOC.) > > A B C D > 13.56 13.93 13.76 13.57 (charging) > 13.32 13.33 13.35 13.36 (resting) > > I find it interesting that the two batteries that have the smallest voltage > drop charging (A and D; within a hundredth of a volt of each other) are the > furthest apart at this momentarily resting voltage. I don't have a mental > model for how batteries providing approximately the same open circuit > voltage have significantly different charge resistance, and particularly > how that difference in charge resistance would be neither directly nor > inversely correlated with open circuit voltage. > > The batteries are speced to charge up to 14.6V and float 13.4-13.6 so I > don't think I'm cooking them. But with two in the string outside the > "float" range I obviously need to keep checking them and not leave them on > "float" indefinitely. > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140202/fe20edf5/attachment.htm > > > _______________________________________________ > 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) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140202/5d74498d/attachment.htm> _______________________________________________ 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)
