Hello, I recently upgraded my lead-acid EV conversion to lithium, specifically 46 CALB 72Ah cells. I've been conservative in my bms settings, not allowing any cell to go above 3.55V or below 2.6V (hopefully "conservative" limits with calb-published limits of 3.65 and 2.5 respectively). I took care when I got the batteries to balance them; I've also been careful to not charge when the temp is below 0C. I've been driving with them for about a month now and have been really happy with the results so far (especially after shedding over a kilopound of battery weight!) But just this week I've become suspicious of one particular cell: now during charging its voltage rises significantly faster than the other cells, and of course once it reaches 3.55V, my charger pauses/ turns off, meaning the other cells don't get as much charge as intended. Then all the cells find a "resting voltage" nearly equal to each other (including the suspect cell). But of course once charging resumes, the one cell still rises faster than the rest.
Today I've had some luck turning down the current on the charger enough so that the shunting in the BMS can (mostly) keep up, allowing the remaining cells to charge. (Though this means of course that charging is taking much longer.) Is this a sign I got a bad cell? I also have a PowerLab8 (that I haven't used in a long time), so I may experiment with it when I get some time later in the week... These cells should still be under warranty, so I can explore that route, but thought I'd get some feedback here first; thanks! Philip Rash http://www.evalbum.com/3381 -- Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com/ _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
