Snow on the array could be a very big problem with the heater load, inverter idle current and anything else that might be left on. Extended periods of heavy clouds can reduce power generation to be less than system's internal losses. It seems like a pretty big gamble to leave an expensive battery bank unattended, that can not go below freezing, and is dependent on array power to prevent freezing.
If AGMs survive in this application, it might be better to stay with this technology. ----- Original Message ----- From: offgridso...@sti.net "RE-wrenches" <re-wrenches@lists.re-wrenches.org> To:"RE-wrenches" <re-wrenches@lists.re-wrenches.org> Cc: Sent:Mon, 26 Feb 2018 10:36:29 -0800 (PST) Subject:Re: [RE-wrenches] heating a lithium battery bank Hello Daniel, I will give this some thought. What lithium make? The ones I have looked at log the temperature for warranty so that might negate the value a bit. The high temp is just as bad in your case here. Since this has been working well I am assuming snow on the panels is not an issue? Building a battery box that was cooled (small fan) from conditioned space is what I have done. The wall between the garage and living space is perfect. This won't help when the house is cold (unattended) much. It won't help if the house is allowed to get hot either. Some of the Lion batteries are actually listed for living space. The LG is. I don't do that with mine though. Hmmm Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ e-mail offgridso...@sti.net text 209 813 0060 > Hello Wrenches, here is a fun one for you all. > > > > The client you all helped me with earlier this year is now considering > changing out their AGM off grid bank with a lithium battery bank before > the > next winter. I looked into this, as we have been eying the various lithium > options for 2+yrs now, but not bit the bullet and really designed a bank > into a system. > > > > The main issue I am trying to consider is this. The cabin is not occupied > during most of the winter, and the batteries are in the unconditioned, but > attached, garage. They drain the plumbing system and shut off all breakers > except the ones that power the internet, chest freezer, and security > system. > As such, the battery bank has routinely gotten below freezing, sometimes > staying there for 1-2 weeks. This is not an issue with AGM's, within > reason. > The battery bank has never gotten below 20F over the last 2 winters, where > the site has seen below zero temps for brief periods. But the AGMs likely > produce more heat during a charge than lithium's, and they have > significantly more thermal mass to ride through the really cold nights. > > > > Lithium batteries, to the best of my knowledge, can be below freezing > during > storage. But to safely charge, they must be above 32F. So the thought was > to > provide an insulated battery box, and design in some small heating system > that is set to 40-45F. The first thought was a low power fiberglass > heating > pad like is sometimes used for livestock to give them a slightly warmed > place to lay down. Then tie that to a thermostat with a sensor on the > battery bank. I would of course need to try to account for the extra load > in > the battery bank sizing. They array is more than is needed right now so I > do > not worry about it's ability to compensate when the sun is shining. > > > > In theory this could be ok, but I worry about the summer. Will the > insulated > enclosure cause the opposite issue during the summer, the batteries > getting > too hot? I have seen the AGM bank go to 110F at one point in Aug 2016. But > with the lower internal resistance of the lithium's, maybe this is less > likely to be an issue. Do any of you wrenches have any experience with > this > unconditioned setup? > > > > With Regards, > > > > Daniel Young, > > NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90 > > _______________________________________________ > 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 > > Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ e-mail offgridso...@sti.net text 209 813 0060 _______________________________________________ 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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