This. A few 60W heater pads wired directly to your panels would probably work just fine to warm the batteries during the day, then let them cool during the night. You could use a simple thermostat to make sure that you aren't heating the batteries on that freak 80*F day.My question concerns the members who might use the cabin in January or February and "they use the lights etc." It's safe to store the batteries in truly cold conditions, but how are those members going to use electricity at the cabin if you have the batteries disconnected? Unless you're going to instruct them to warm up the cabin, ensuring the cells are also brought up to well above freezing, and then connect them so they can use power during their stay, I don't see how lithium is going to work for you.
You mention you have solar panels at the cabin. If the batteries were stored in an insulated space, with one of those flat electric heating elements used to warm seed trays, that would keep any battery type you used warm enough to safely charge them, allowing you to keep the SCC connected and the system available for use. They draw very little current, such that it would only take the occasional warm/sunny day to keep your batteries topped off. If you were really worried about it, you could run that warming pad off one or two of the existing AGM's, so the lithium battery bank stays warm. Solar keeps the lithiums charged up and a conventional trickle charger powered by the inverter keeps the AGM's topped off.
You've got the means to keep them reasonably warm and keep the batteries charged.
ETA - Have you considered lithium-titanate, since it's a stationary installation?
I don't think I'd bother with a 12v heater. Just wire the 120v pad directly to the panel DC buss, possibly through a thermostat relay. They are just resistance wire in a plastic case.I am going to procure a 12v and also a 120v heater pad. My main battery being a fairly large sla chemistry, and my inverter being a fairly large all in one, both will have an application, but I plan to leave both the lip04 disconnected. Thank you up north for reminding on the bms. This should be as simple as disconnecting bat + and -? I have the overkill solar bms.
I have a similar question about disconnecting the BMS. I have a battery disconnect mounted on the battery box but this is after the BMS and Smart Shunt that is inside the box. I realize there is a resting mA draw when the BMS is powered and I would imagine the same for the Smart Shunt. Obviously, unhooking the large negative cable from the battery to the BMS will work for disconnecting that device but what about just installing a switch to interrupt the + small wire that powers the BMS and something similar for the Smart Shunt?I am going to procure a 12v and also a 120v heater pad. My main battery being a fairly large sla chemistry, and my inverter being a fairly large all in one, both will have an application, but I plan to leave both the lip04 disconnected. Thank you up north for reminding on the bms. This should be as simple as disconnecting bat + and -? I have the overkill solar bms.
what about just installing a switch to interrupt the + small wire that powers the BMS and something similar for the Smart Shunt?
Maybe disconnect the batteries for that time. And use some lead acid during that time? We have a similar situation and everyone knows that in the winter we really rough it with limited power. Just how it is in the winter. I have shown up at 4 degrees inside temp. Our 400w panel keeps the lead acid batteries high enough for some limited light. Then we use led lamps.I have a similar question about disconnecting the BMS. I have a battery disconnect mounted on the battery box but this is after the BMS and Smart Shunt that is inside the box. I realize there is a resting mA draw when the BMS is powered and I would imagine the same for the Smart Shunt. Obviously, unhooking the large negative cable from the battery to the BMS will work for disconnecting that device but what about just installing a switch to interrupt the + small wire that powers the BMS and something similar for the Smart Shunt?
In theory it seems like this would work because it essentially shuts down the devices.
I ask this because I can mount a small switch outside the box that does this but to disconnect any of the large cables would require one to get into the box and unbolt cables. As I stated before, we have several other members that use this cabin. I don't want ANY of them opening the battery box and messing around in there.
Any suggestions welcome.
I have decided against a heated box for multiple reasons. Just suffice to say I am not going that route. This battery will be unattended for 4+ months and the person who will be the last to leave the cabin for the winter and the first to re-open the cabin in the Spring could be any of 9 members most of which want nothing to do with the solar system except to use the electricity that it provides. Unfortunately, I do not live close by the cabin to do any monitoring of opening or closing the cabin so I need to make shutting down and powering the system back up as simple as humanly possible. I have a simple on/off battery disconnect on our present AGM system now and they could handle that but asking much more than one more switch to toggle is asking too much. Not an ideal situation but it is what it is.
Sorry I didn't see this earlier. Your situation is very similar to mine, and ironically it drove to a completely different conclusion.I have decided against a heated box for multiple reasons. Just suffice to say I am not going that route. This battery will be unattended for 4+ months and the person who will be the last to leave the cabin for the winter and the first to re-open the cabin in the Spring could be any of 9 members most of which want nothing to do with the solar system except to use the electricity that it provides. Unfortunately, I do not live close by the cabin to do any monitoring of opening or closing the cabin so I need to make shutting down and powering the system back up as simple as humanly possible. I have a simple on/off battery disconnect on our present AGM system now and they could handle that but asking much more than one more switch to toggle is asking too much. Not an ideal situation but it is what it is.
Given the respect that you obviously garner here, I read the above with great interest given my similar 'up north' scenario:"..So again, my opinion, but storing them at any state of charge except fully drained or totally full for extended periods of time (I've had at least one test cell in the cold for 6 months without any loss of capacity) is not an issue."
certain (low budget only?) brand new LiPO4 cells have individual low-draw/bad cell problems right out of the box and that this may be a luck of the draw.
My point is this if any cell does not test 'perfect' at any given time and if any capacity loss can somehow(?) be long term approximated/quantified before storage begins...
the educated opinion above and any further cold cell storage studies will be a Godsend so that we can then use technology (heaters, auto cut-offs, etc.) to deal only with segregated (known) even minor bad actors...with all other cells simply wrapped?/put aside in just as warm a place as possible.