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Anyone------can I safely STORE Lifepo4 battery in cold weather

Consider this my personal opinion. It's based on my own experience and some research papers I read at some point in the past, but none the less an opinion. Storing LiFePO4 cells for longer periods of time is not an issue, and the colder it is, the better - as long as no energy is put into or taken out of the battery (which includes power for the BMS, so turn the BMS off). Cold is an excellent way to halt or slow down chemical processes, and it's the reason cold also slows down calendar aging in the cells. 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.
 
After doing more research and reading studies like the one referenced above in this thread your opinion on the subject aligns with my present thinking on the matter.
I have read several of your posts on this forum and have a great amount of respect for your posts and opinions. I want to thank you for your multiple posts on this particular thread.

I still think this would be a great experiment for Andy of the Off Grid Garage to do but the experiment would take (obviously) many months to complete and even then the question of any long term effect on cycle life would be unanswered. And, with the type of weather he gets down under he would have to use a freezer to do the test. I wish he experienced the cold weather like you because if he did, I think this topic would be of paramount importance to him.

Once again thank you!
 
Not sure if you saw this, but I did a charge test at -17C to see if there is any immediate effect. There isn't. (I posted it in this thread, so you did)
I'm running a longer term test now. Too bad it takes so much time to get any data that have relevance to long term effects.
 
I did see it as well as some results of a paper that curiouscarbon posted. Both point towards to your (and now mine) opinion on the subject. I think we have agreement!
 
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?
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.
 
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 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 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.
 
the 120v pad is the garden variety for sprouting seeds with thermostat that goes on and off - I was going to use this when on site and charging and discharging.
The 12v I was going to wire on a breaker and source power from the sla, those nifty thermostats posted in the other thread are all out of stock online now unfortunately.
 
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?

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.
 
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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.
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 am looking into silicate salt batteries if anyone had experience with them.
 
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.

Our Colorado mountain cabin is closed up in mid-/late-November every year, and is not opened back up until early May the following year. The cabin is co-owned by myself and my two siblings (and our families). Both my siblings live within an hour drive of the cabin, and I live about 6 hours from the cabin. I'm not the one who closes the cabin down in the fall, and I'm not the one who opens it up in the Spring. I designed the solar power system, and am the primary watchful hen over it. My siblings and their families just want to arrive at the cabin and take the inverter out of standby and start using it. When they leave, then know to put the inverter back in standby. Other than that, I'm the only one who does anything to the system. No one touches the inverter / charge controller settings, any of the wires, etc. Doesn't that sound familiar to you?

When I decided to transition from AGM to LiFePO4 batteries, I realized one of the biggest things I needed to do was make it so no one had to do anything different. They should be able to just take the inverter out of standby to use the electricity, and put it back in standby when their visit was over. That includes the infrequent visits over the winter when someone decides to cross country ski or snowmobile in. To me, that meant I needed to keep the batteries warm enough to operate normally. So I built an insulated box with thermostatically controlled heating pads. The entire system is documented in this thread: https://diysolarforum.com/threads/horseflys-cabin-solar-lifepo4-upgrade.27472/

The operation will be pretty simple. I may or may not disable and enable the heating system on my spring and fall visits to the cabin. However, if I just left it all it probably would be fine.

I will admit that I thought about doing what you have mostly been discussing: Disconnecting the batteries, discharged to a safe level, and leaving them disconnected until spring and they were warmed enough to operate safely. That to me seemed like a disaster waiting to happen. Someone would show up at the cabin and want some electricity, and so would try to hook everything back up. God only knows how it would work out.
 
"..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."
Given the respect that you obviously garner here, I read the above with great interest given my similar 'up north' scenario:
I have zero interest in relying on unmonitored box heaters or even temp. sensors while using chargers working 24/7 during cold storage for obvious reasons. (my FLA cells being the exception) ...
...tempered by...
...my 'guess' that 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.
The latter speculation above comes from my recently charging a bank of 3 brand new 200Ah 12V Chins cells. All three charged sufficiently until I tested them again by simply unplugging/plugging the charger back in to make certain that I could repeat the feat. This time around, one cell took an additional ten minutes or so to top off which I will follow up on with a load test(?) on all three after they have rested.

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.

I would be happy as a clam if I could employ the K.I.S.S principle, make educated guesses and take my chances using far less power and never worrying about failures of anything save for the charger itself (unlikely) hooked up to one questionable cell at a time.

Example: I was told yesterday by a major trolling motor manufacturer call-in service rep. that they are currently estimating at least 30% out of the box minor and major failures in the cell components of the FLAs which their customers are purchasing. I'm not saying that one of my Chins has an individual cell issue yet I'd rather troubleshoot/quantify it right away (which frankly I need help on) and treat it differently than any other in a no charge cold storage ideal scenario should further studies prove the opinion above, which I also believe to be reasonable given the author's reputation alone.
 
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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.

Personally, if it's a cell that is bad to begin with... not much you can really do about that. It's one of the reasons I DIY my packs: off the shelf systems don't offer the flexibility to service individual cells. If one of my cells die in operation/storage because if was defective to begin with, so be it, I'll replace it.

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...

If you can determine the rate of self discharge, you can. However, in my opinion, this is trying to patch up a bad battery. They should not self discharge more than a typical LiFePO4 cell. Instead, if you have this kind of application and want the peace of mind, either DIY your own or save up some money to buy a higher quality battery.

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.


"Storing batteries below freezing is fine, even at very low temperatures such as -40 Centigrade (that is the same in Fahrenheit), or even less! The electrolyte in LiFePO4 cells does not contain any water, so even when it freezes (which happens around -40 Centigrade, depending on the particular formulation) it does not expand, and does not damage the cells. Just let the battery warm up a bit before you start discharging it again, which is OK at -20 Centigrade and above. You will see an apparent loss of capacity when discharging at below-freezing temperatures that reverses when the battery gets above freezing, and there is a slightly accelerated effect on aging. Storing them at low temperatures is certainly much better than storage at high temperatures: Calendar aging slows down dramatically at low temperatures. Try to avoid storing them at 45 Centigrade and above, and try to avoid storing them completely full if possible (or nearly empty)."
 
Thanks for taking the time to educate, upnorth (my state's extreme 'upnorth' has a long thriving Finnish culture complete with a Finnish liberal arts college). I should have stated that these cells are used for a marine application. I am still waiting for someone to share a well fitting (universal) DIY battery enclosure product line which marries these reasonably priced cells to the outdoor world. This reality(?) forced me to cut corners with the decently sealed Chins. This also prompted me to ask regarding the 'how tos' of cell degradation measurement as related to cold storage or not. When I hear the 'never nearly empty' storage mantra, I cringe a bit when dealing with a constantly self-discharging cell not being charged regularly reaching this point easily.
Saving up the money/rolling the dice to buy 'higher quality' Chinese LiP04 cells is obviously good advice yet not an option for me given that I have not even drained these new ones for the first time.
I guess that my question is this:
Is my MinnKota 460PCL; 15A; latest generation; 4 bank LiP04 charger telling me enough of a story given the above scenario to make a bad cell educated guess (charge for the first time; it's charged...unplug charger then plug back in; it's not yet will charge in 10 minutes or so)...and can anyone direct meet to the end all/be all method of quantitatively testing LiP04s sealed cells for self-discharge issues?
In other words, I have no problem cold storing any LiP04 cell at the right discharge level save for a known bad actor which would get pulled and put on a smart charger 24/7 for obvious reasons.
 
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Because LiFePO4 has a such a low self discharge, the only thing to really worry about is how much the BMS draws. I have had my cells sit well below 50% for months at a time without issues, but if you're at very low state of charge (below BMS cut-off) and the BMS can not turn itself off and keeps draining the cells, you can get damage.
 
Lithium cells are not affected by extreme temperatures if the battery pack is not being used. It's not good to store lithium batteries in very cold temperatures for extended periods of time because that could cause the ABS casing of the battery pack to potentially crack.
 
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