These issues are not lost on me for sure. I have to plan out a new protective setup to try to ensure that if the temperatures drop and the battery bank hits LVD, that the array cannot just charge the battery back up on it's own. Possibly some sort of temperature dependent relay or shunt trip breaker on the battery bank to ensure that below 35F the battery must be manually warmed to resume operation, or the system waits until the battery warms on it's own before allowing the CC's or even a generator to charge them.
My understanding is that the lithium's can go below freezing easily, but they just cannot be charged when below freezing. They can sit down to -5F if not being charged, they can even be under discharge down to that in some cases. But adding controls to allow discharge, but not charge is likely a bit too much, best to just isolate the battery bank if below 32-35F in my opinion, which is what I plan to try to accomplish. Ideally someone is there to watch the batteries, but that simply is not an option. And the client is not likely to want a new AGM bank. But they will have to decide between the pro's and con's. All I can do is give them the info, and the choice. With Regards, Daniel Young, NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90 -----Original Message----- From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Angelini Offgrid Solar Sent: Tuesday, February 27, 2018 1:14 PM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] heating a lithium battery bank The LG RESU series will trip it's breaker at around 10% Soc. It will require a human unless the LVD on the inverter is set higher than the battery. Yes Sir it is our responsibility to educate our users or have plane tickets (: Will be installing the Discover battery soon into Xanbus. Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ e-mail offgridso...@sti.net text 209 813 0060 > Hi Drake, > > I agree. Li-ion batteries, like lead batteries, should always have a > human overseer. This is a difficult reality to convey in our > set-it-forget it, automated world. > > One function of a Li-ion battery EMS or BMS is to prevent over discharge. > Once any battery cell reaches the lower limit, the battery will turn off. > For many systems, once charge current is again detected, the battery > will turn on. Some will not and require a user to turn the battery > back on. You can also install an external LVD device to stop power use at a higher SoC. > > As wrenches, its our responsibility to know our product and educate > the customer. Too often, this does not happen. > > Larry Crutcher > Starlight Solar Power Systems > > > > > > > On Feb 27, 2018, at 7:11 AM, drake.chamber...@redwoodalliance.org wrote: > > 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/maillis >> t.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 > > _______________________________________________ > 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 > > > _______________________________________________ > 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 _______________________________________________ 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
