This chart from Trojan is very customer good education. Battery electrolyte is very close to water at low SOC. http://www.trojanbattery.com/pdf/WP_DeepCycleBatteryStorage_0512.pdf
Also, note that many MPPT charge controllers won't "wake up" and start charging, even on a sunny day, if battery voltage is below 9.5V +/-, unlike some older PWM units without the fancy computer inside which will wake up with the sun. So the solution is to "jump start" the voltage, even if you have to center tap charge for a few minutes to raise voltage before the controller wakes up and the sun can take over (photo, center tapped 24v battery bank with 12v wakeup call). I'd give saving the battery bank a shot unless you can see physical damage inside or out from the freezing. In any case, you'll know very quickly when you start charging if it has caused an internal short. In my experience, good batteries can take 0%+/- SOC a few times--they have certainly lost a lot of capacity but might still have some life in them. If physical damage occurred, send them to recycle center. Good luck! Dan Fink Adjunct Professor, Ecotech Institute IREC Certified Instructor™ for: ~ PV Installation Professional ~ Small Wind Installer Executive Director, Buckville Energy NABCEP Accredited Continuing Education Providers™ 970.672.4342 On Thu, Dec 3, 2015 at 7:00 AM, Feather River Solar Electric < i...@frenergy.net> wrote: > Hey Folks, > > I came across an off-gridder yesterday whom was getting zero > support from the dealer he had purchased his small system from, self > installed, batteries in a lightly insulated box outside. When I inspected > the electrolyte levels I discovered it was frozen in some cells, the > voltage of the 48 volt pack was ~8 volts, I didn't check individual > batteries due to these facts...I'd seen "enough". Recently temps have been > in the high teens, though we are back up to low 30's. > > He does not have a genny or battery charger! I have a DC genny > which I could use to charge these batteries but should I waste my time and > his money trying to save them? Others' experience with this situation? > > TIA, > > Bill > > -- > Feather River Solar Electric > Bill Battagin, Owner > 4291 Nelson St. > Taylorsville, CA 95983530.284.7849 > CA Lic 874049www.frenergy.net > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > >
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