I have reversed UB batteries in the past, in an EV with a *long* series string of batteries (312V, so 26x UB121100) and if a cell has been reversed, it loses capacity and thus will reverse earlier next time. You will find such cells by checking for warmer compartments in the 6-cell battery cases. On the other hand, I have also bought new batteries that someone discharged and then let sit at 0V for a year in their garage. It took about 3 days of applying voltage before it started drawing any appreciable current, after that it charged normally. So, any *smart* battery charger will refuse to resurrect such a battery. What I do is use a current limited lab supply, for example set for 100mA and 30V, connect to the battery and simply wait. After a while (and this can be several days) the voltage drops to 12V because the battery starts charging at more than 100mA. After that you can use a regular charger, though I like to set the lab supply for 14.2V at about 0.1C so for a 35Ah battery I can use a small 3 Amp supply. I keep the battery connected until the current draw at 14.2V becomes very small, less than 0.1 Amp. No problem to leave it attached to the battery an extra day. This revives the battery as much as possible, after that you can test it in normal operation or with a tester to see its capacity and determine if you want to continue using it. Good luck! Cor.
On Tue, Dec 7, 2021 at 10:42 PM EV List Lackey via EV <ev@lists.evdl.org> wrote: > > A 12v battery is considered flat when its open circuit voltage is 11.8 > volts. Since yours were at ~5 volts, it's fairly likely that you've > reversed some cells. That's most definitely not good. > > Still, you might get lucky, and it can't hurt to give them a long, slow > equalizing charge. Cycle them a few times, and then test their capacity. > While you're at it, also test the other two for capacity. > > If you decide they have enough sock left to give you some use, but are > definitely less healthy than the others, I recommend building a Lee Hart > Batt-bridge, so you don't over-discharge and reverse them again. > > http://evdl.org/pages/battbridge.html > > If they turn out to be at death's door, this might be an ideal time to find > another chore for the 2 remaining good ones, and treat yourself and your Ox > to a complete new set. > > Some here will probalby suggest that you consider lithium, but I'll leave > that discussion to them, as I'm not really qualified. > > Good luck! I hope it works out. > > David Roden, EVDL moderator & general lackey > > To reach me, don't reply to this message; I won't get it. Use my > offlist address here : http://evdl.org/help/index.html#supt > > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Most people here [in the US] don't want an abrupt reshuffling > of everything. That's why we've had only one revolution. It's > why we've fought off the metric system all these years, and > thank heaven we have. > > -- Fox anchor Tucker Carlson > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
