August, The current Tesla (AC coupled only) would be a challenge for sure! I do like the 13KWH for the price. I hope they do something as everything I have looked at beside the LG is over $1,000 (wholesale) per ueable KWH. Hope this changes. --Dave
> As I mentioned on a related post, Tesla's Powerwall has an active heating > feature where it will use some of its own energy to raise cell > temperature. > Obviously this means that it will need to be charged throughout the cold > season using some amount of PV energy to do so (I think I heard 250 Wh per > heating cycle depending on temps?). I understand that Tesla's offgrid > Powerwall isn't ready for prime time yet. > > August > > *August Goers* > > Luminalt Energy Corporation > > > On Wed, Feb 28, 2018 at 8:55 AM, Bill Hoffer <suneng...@gmail.com> wrote: > >> Daniel >> >> Why are we having to deal with low temp charging? Litium batteries >> already have cell temp monitoring and relays to shut down individual >> cells >> when they over temp. How hard would it be to open the relay at low >> temps >> too? Seems like something the lithium battery folks should have already >> thought of? >> >> Bill hoffer >> >> >> On Feb 28, 2018 8:15 AM, "Daniel Young" <dyo...@dovetailsolar.com> >> wrote: >> >> 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: >> > 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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/ 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