It's very easy to test a battery. Take it out of the pack and try to charge it. It will rise in voltage or not. You BMS boards probably have a minimum voltage to operate and cell fell below that voltage and does not imply the cells is bad. After you charge it then hook up to a know load and measure the capacity of the cell.
Sent from my iPhone > On Aug 3, 2017, at 3:34 PM, mnevans via EV <[email protected]> wrote: > > I'm new to this discussion list, so I ask your patience: my understanding of > EV systems and Li-ion batteries is limited. > > The question is: replace a bad battery in a pack of 19, or make the pack 2 > batteries smaller and suffer an unknown loss of voltage and range? > > Background: > > I think I have a bad battery in one of 19 batteries that is in the second > bank of a 4 bank x 19 CALB CA40FI battery pack. The battery pack is used in > a 10KW battery that is part of a Plug-In Supply conversion of a 2004 Prius > to a plug-in Prius. Robb Protheroe installed the system in late 2014, and > it has seen about 10K miles, maybe 60% of that in all electric mode, about > 900 partial or full charge cycles. > > The evidence that the battery is bad is an incomplete loop circuit. I found > that the battery management board atop the suspect battery was not powered, > and moving that BMS board to another battery adjacent powered it. The > suspect battery was at 2.67V. The others adjacent are at 3.0V. Originally > they were all balanced at 3.26-3.27V. > > Robb Protheroe at Plug-In Supply suggested replacing the battery with a new > one. Unfortunately CALB no longer makes this 40Ah battery, but the Sinopoly > or Winston 40Ah prismatic cells are nearly the same dimensions and > specifications. It looks like I can get a replacement for about USD$60 > including shipping to me in Maryland USA, using www.ev-power.eu (a US > supplier wanted $42 shipping for a $55 cell). > > The other option is to remove the bad battery and the one adjacent, and > carry on with a lower voltage pack. Robb is unsure whether the range loss > would be proportional (7%, I can live with that), or more, due to "voltage > sag" and age of cells. He suggested I ask you, so here I am. > > Questions: > > 1. Would you recommend replacing or removing batteries from my pack? > > 2. If removing, what is your guess on loss of range due to lower pack V, > voltage sag? > > 3. If replacing, do you expect the new cell to assume the lifetime of the > rest of the batteries in the pack, as others have written on this listserv? > > So far I am thinking to try removing, see how the range is affected by > testing on a known route that is longer than the original hybrid range with > this pack installed. If unacceptably worse, add back the replacement cell. > If not, carry on with the slightly smaller battery pack. But I would be > grateful for the wisdom of the list. > > Thank you in advance for your help, > Mike > > > > -- > View this message in context: > http://electric-vehicle-discussion-list.413529.n4.nabble.com/replacement-or-removal-of-suspected-bad-40Ah-prismatic-LiFePO4-battery-tp4687552.html > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at 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 Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
