Hi Daniel and Larry, I have a LI-FePO system, Simpliphy 10 kWh it is on its third winter, the batteries are unconditioned but in a box. I am now concerned, as I worked as closely with Simpliphy as I could. They did not caution me about the operation in the cold. The batteries sit and have no load other than the charge controller. This is similar to Daniel's system except he has some loads that run down the battery. If the sun comes out the batteries will get a chance to charge. The charge controller is a Morningstar Tristar 150V MPPT 60 A (not using the roll-back feature) I think I should pay a visit to this customer's cabin.
On Mon, Feb 26, 2018 at 10:56 AM, Daniel Young <dyo...@dovetailsolar.com> wrote: > 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 > > >
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