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

[Xhumeka]

Just a warning about using solar panels to power a heating mat for your battery - you need to make sure the solar panels themselves don't get covered in snow for months at a time.

I'm near Bancroft Ontario Canada, and one winter I disconnected my inverter but left my midnite classic 150 charge controller connected to my flooded lead acid batteries from Nov 1st to May 1st thinking it was a good idea to keep the batteries topped off. When I opened up in the spring, everything seemed fine but checking the midnite classic logs there must have been snow on my panels from mid-Jan until at least end of Feb, because I saw the battery bank voltage slowly drop by a few mV each day until it dipped below 10v and the classic turned off. It came back on sometime in March after the snow melted from the panels and the midnite somehow kicked back in, but clearly this was damaging to my batteries and wouldn't want it to happen again. Going that route again, I'd have to somehow devise a way to keep the snow off my solar panels - but something could always go wrong.

@harpo - how did this winter go for you? And you never answered the question about what happens when those infrequent visitors show up in the middle of the winter... if you're disconnecting the batteries, how are they "turning on lights?"

 

[Supervstech]

Just a warning about using solar panels to power a heating mat for your battery - you need to make sure the solar panels themselves don't get covered in snow for months at a time.

I'm near Bancroft Ontario Canada, and one winter I disconnected my inverter but left my midnite classic 150 charge controller connected to my flooded lead acid batteries from Nov 1st to May 1st thinking it was a good idea to keep the batteries topped off. When I opened up in the spring, everything seemed fine but checking the midnite classic logs there must have been snow on my panels from mid-Jan until at least end of Feb, because I saw the battery bank voltage slowly drop by a few mV each day until it dipped below 10v and the classic turned off. It came back on sometime in March after the snow melted from the panels and the midnite somehow kicked back in, but clearly this was damaging to my batteries and wouldn't want it to happen again. Going that route again, I'd have to somehow devise a way to keep the snow off my solar panels - but something could always go wrong.

@harpo - how did this winter go for you? And you never answered the question about what happens when those infrequent visitors show up in the middle of the winter... if you're disconnecting the batteries, how are they "turning on lights?"

I remember what snow looks like... but it's been a long time since I've seen any. I don't miss it much.

 

[Horsefly]

Just a warning about using solar panels to power a heating mat for your battery - you need to make sure the solar panels themselves don't get covered in snow for months at a time.

I'm near Bancroft Ontario Canada, and one winter I disconnected my inverter but left my midnite classic 150 charge controller connected to my flooded lead acid batteries from Nov 1st to May 1st thinking it was a good idea to keep the batteries topped off. When I opened up in the spring, everything seemed fine but checking the midnite classic logs there must have been snow on my panels from mid-Jan until at least end of Feb, because I saw the battery bank voltage slowly drop by a few mV each day until it dipped below 10v and the classic turned off. It came back on sometime in March after the snow melted from the panels and the midnite somehow kicked back in, but clearly this was damaging to my batteries and wouldn't want it to happen again. Going that route again, I'd have to somehow devise a way to keep the snow off my solar panels - but something could always go wrong.

@harpo - how did this winter go for you? And you never answered the question about what happens when those infrequent visitors show up in the middle of the winter... if you're disconnecting the batteries, how are they "turning on lights?"

That's a really good point to make, coming from a hard lesson you yourself had to learn.

I'm hoping my system can avoid such an issue, as I've got some failsafe items to protect.

First of all, the BMS should stop all discharge below the LVCO of the cells. That obviously wouldn't have helped you @Xhumeka with your FLA, but it should help for LiFePO4.

Secondly, my heating system will be disabled if the battery gets below a set voltage. So if the snow covered the panels for a very long time the system would essentially go into hibernation until spring. The heating would stop, and then the low-temp charging cutoff would prevent charging the batteries until they warmed. When the sun hits the panels again (hopefully before the battery reaches low voltage cutoff), the charge controller would raise the voltage and allow the heater to run again.

Finally, even though our cabin is at 9,000 ft elevation in the Colorado mountains, the air is very dry and the sun is intense - even in winter. For the three previous winters we never had snow covering the 45° tilted panels for more than a couple of days at a time. My tests seem to show that my heaters can keep the battery warm for several weeks before the voltage gets too low.

 

[h2onet]

I have a similar situation where I have a cabin in the Colorado mountains that is unoccupied during the winter. I am currently building a tiny greenhouse/hot box, just big enough for the battery and a little insulation behind it, where I'm going to set my battery inside the cabin in a South facing window. I'm hoping the thermal mass of the battery and the Sun heating up the inside of the box during the day will keep it slightly warm overnight.

 

[Yurtdweller]

I remember what snow looks like... but it's been a long time since I've seen any. I don't miss it much.

I know this topic is old, but regarding wintertime and snow covering, could you not put your panels fully vertical in the winter? If you're not using lots of juice, the reduced panel efficiency shouldn't be a major issue, and if there's danger of snow on the panels, then there's snow on the ground, bouncing uv into those panels anyway. Not to mention, the sun is at a low angle anyway, so vertical panels, again, should be effective.

 

[JoeHam]

Plenty of discussion about vertical panel orientation :

Search results for query: Vertical panel

diysolarforum.com

It’s just a compromise amongst priorities.

 

[harpo]

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.

UPDATE:
My son unexpectedly went up to the cabin last night and he sent me a screen shot of the cell voltages. These values are after the battery sat dormant for 126 days, several of which when the temperature was well below freezing, at 55% SOC with all loads disconnected except the Overkill BMS and Victron Smart Shunt. I confirmed that both of these components have very low power consumption when asleep and, according to my calculations, would have consumed less than 10 amps total over the dormant time period.

The question I did not know was what effect the low temperatures would have and how much natural self-discharge (expected very little but did not know for sure) would take place.

Since the Smart Shunt will not register very small current draws (mA) I knew whatever SOC it showed after the dormant period would likely be inaccurate. So, all I had to go by was individual cell voltages which, as you know is not a good indicator of SOC but would give me information if the end voltages were below 3.0V/cell.

The cell voltages were all around 3.28 with a delta of .004v when the dormant period began. The screen shot my son sent me last night revealed absolutely no change in either of those parameters. I am not going to try and talk him through a "controlled" charging process where one could assess how many amps it would take to fully re-charge the battery thus giving me data to calculate what the actual SOC was following the dormant period. Therefore, I cannot say with any certainty how much SOC the battery lost during the dormant period but I learned that the cells survived the winter just fine the way I stored them. I could not be happier.

Thanks to many who commented on the DIY Solar Power Forum, especially upnorthandpersonal and Curiouscarbon, for all their input when I tried to gather data on how LifePO4 cells would react to cold, no load storage. Most of the comments lead me to believe the battery would be fine as long as I disconnected the loads and solar panels and left the battery in a SOC of roughly 50%. That is what I did and, apparently, all is well.

 

[Old_Skewler]

Thanks to many who commented on the DIY Solar Power Forum, especially upnorthandpersonal and Curiouscarbon, for all their input when I tried to gather data on how LifePO4 cells would react to cold, no load storage. Most of the comments lead me to believe the battery would be fine as long as I disconnected the loads and solar panels and left the battery in a SOC of roughly 50%. That is what I did and, apparently, all is well.

Hi Harpo,

I am in a similar situation near PA and this past winter I decided to haul my EG4 battery back to my winter residence because I wasn't sure. So in summary, is it okay to leave these batteries in the cold weather when NOT in use (for storage purposes only)?

 

[Supervstech]

Yes, no issues storing in cold… disconnected from any charge source. Or, if the BMS has low temp protection, it will prevent any charging when cold.

 

[harpo]

My opinion: state of charge isn't too important. Somewhere between 30% and 80% for a month or two is fine.

Hi Upnorthandpersonal. This thread which was started in 2021 had some tremendous references on cold weather storage. I particularly like the research experimental data presented. This so so much better than just personal observational information.
I am contacting you now to see if, to your knowledge, there has been any new information on the subject. It has been almost 2 years since the last entry in this thread.
I think you know that after perusing the data presented by yourself, curiouscarbon and others, I left my Lifepo4 battery I assembled from raw cells at the cabin over the winter for 5 months. I unhooked all load, disconnected any charging from the solar panels and left the battery at 55% SOC.
They did fine just as you and others predicted.
The reason I am asking if there has been any other data published about this chemistry and cold weather storage is that I am seeing some commercial battery manufacturers, including BattleBorn and others, recommend storing at 100% charge. I cannot find out why they recommend this SOC for storage.
Perhaps, as you stated in one of your entries in this thread, SOC is not really all that important as long as it is "between 30-80%.
I closed up the cabin this past weekend and did the same as I did the previous year (since it seemed to work out fine). I am fairly confident it will do fine just as it did last year.
I just wondering if there is any new information on the subject that you are aware of.

 

[upnorthandpersonal]

It's likely because (this is speculation) the BMS they have inside needs power, continues powering itself from the battery even after low voltage disconnect. My JKs for reference will turn themselves completely off at that point, but I don't think the JBD/Overkill does.

As far as I know, there isn't any other research on this at this time, and all the past research and recommendations are still valid. I definitely didn't change my process.

 

[itech20]

First off, many thanks to everyone who has participated in this thread. I'm grateful to have found it.

My wife and I have an off grid property in Michigan that we use intermittently. I recently installed an EG4 6000XP inverter and LiFePO4 battery bank, and will be adding a solar array in the spring. However, I expect to have lengthy periods during the winter where the panels are snow covered and I'm not there to clean them.

The batteries are SOK 48 volt rackmount units which have pretty robust low temperature protection built into the BMS.

SOK 48V 100Ah PRO Server Rack Battery - User Serviceable | Current Connected

SOK 48V Server Rack Battery: 4000+ cycle life, UL1973 & UL9540A certified, UL9540 pending, Built-In Smart BMS, 10 year warranty & support!

www.currentconnected.com

As a result, I've been thinking quite a bit about the issues covered here.

It seems prudent to build an insulated enclosure for the batteries and set up some kind of heating. However, it's unlikely that the solar input will reliably provide enough energy, on average, to cover both the inverter standby load and enough heat input to keep the batteries above minimum charging temperature.

I have a generator but I'm uneasy about having it run automatically to top up the difference. It's just not something I want to depend on.

As a result, I'm thinking in more detail about how to run things if the equipment is fully shut down during the dark and cold periods. We'd like the option of visiting and using the place at least occasionally even in the winter months.

Based on this thread I'm thinking about the following rough procedure.

• When leaving and shutting down, I'll ensure that the batteries are at a relatively high state of charge, potentially up to 100%. I'll then shut things down entirely. BMS off, Inverter off, etc. The property will be entirely cold and dark.
• If I arrive and the batteries are above minimum discharge temperature, I'll use the battery bank itself to run the heaters inside the enclosure until I'm above minimum charging temperature. (The battery internal resistance will also help here.) This will have the side effect of bringing the pack temperature up to a point where I'm not dealing with lost capacity due to temperature.
• If I arrive and the batteries are below minimum discharge temperature, I'll use the generator or propane heat to warm the batteries up to the minimum discharge temperature, then slot into the step above. It remains to be seen if we'll actually want to be there if it has been below -4F / -20C long enough for the insulated battery bank to get this cold but I at least want to have a plan in place.

Based on what @upnorthandpersonal has shared about their experience, I'm not going to worry too much about extended storage at very low temperatures. It seems, on balance, that this will slow the calendar aging process, and that as long as I warm things back up before exercising the packs extensively, I should be fine. As this is an intermittent use property, calendar age is the more likely issue anyway.

I'll try to report back on my experience as time goes on.

 

[justgary]

Even snow-covered panels should produce some power. You could try isolating the batteries and routing all solar power to a heating pad with a simple temperature controller to make sure you don't exceed 75*F or so. Whatever sun you do get would help keep the batteries out of deep freeze.

Good insulation and proximity to the earth (put the batteries on the floor, away from exterior walls) would help maintain a stable mean temperature also.

 

[itech20]

I like the "best effort heating directly from solar output" idea somewhat.

Getting a little fancier, I can start to imagine an inverter state machine of sorts for this.

You'd have an AC based heating system with a thermostatic cutoff like you describe.

Then you'd want the inverter to follow something like:

State 1 - SOC between 70 and 100 - stay on - Provide standby inverter power and AC power to the heating system
State 2 - SOC below 70 - don't draw standby or heat from the battery. Provide AC and charging as available from solar input. That is, shut down when there is no solar input.

The SOK batteries will shut off the BMS after 24 hours of low/no activity. This introduces a possible scenario where you linger in State 2, providing a small amount of charge every day but not enough to keep up against the standby draw of the BMS, so you might need to add:

State 3- SOC below 50 - stop trying at all, you're not keeping up and you're going to drain the pack entirely. Leave 50 percent in there for a true cold/dark arrival.

 

[Bobscoldcamp]

Thank you for the responses so far.
I have done a search both on the internet and here on the forum. There just doesn't seem to be a consensus. Most everyone agrees that 1) never charge or attempt to charge the LifePO4 battery below 32 degrees F. 2) if storing for more than a month the battery should be left at partial charge somewhere between 40-60%.
To clarify more on my situation: 1) The battery will be disconnected from all sources of load AND charge. Therefore, there will be absolutely no load on the battery and solar panels will be disconnected via circuit breaker from the SCC. 2) Temperatures in Northern PA in the winter will vary from a high of 35-40 to a low of normally 0-30 degrees F. with occasional days below zero. 3) the batteries will sit dormmate for at least 3-4 cold weather months.

There is a lengthy thread here on this site talking about cold weather and LifePO4. I have read all 28 pages of that thread and still can't see a consensus on my specific circumstance. Most just say to take your batteries out of the cold environment and indoors during the cold weather/winter. As stated, that is not realistic for my application. Since I am building this battery from raw cells there is no manufacturer to call about this issue and even then there is no consensus. For instance, I contacted Battleborn. They said it was ok to store THEIR battery long term in cold but to FULLY charge it first. Other manufactures (ReLion and Lion Energy) wouldn't say if it would harm their battery or not but recommended a heating element or their own battery with an internal heating element. This will not work because this is a resistive load that will discharge the battery down to nothing eventually because there is no charging going on at all. So, manufacturers of commercial LifePO4 batteries can't agree on this issue.

This would be a good experiment for Andy of the Off Grid Garage but it never gets cold enough in Australia. He'd have to use a freezer and it would take him months to complete. He is the only one I can find that continually does experiments on these batteries made from raw cells just for the sake of finding out how this chemistry reacts to different circumstances.

Hope someone can point me to scientific paper on this subject or an experiment as mentioned above.

I desperately want to convert our small off grid hunting cabin solar system from AGM to LifePO4. However, I am getting conflicting information about these batteries being STORED for months at a time in sub freezing temperatures.

Yes, I know this it is not ideal to store them in cold weather but that is the reality of my situation. It is impractical to remove the batteries, for instance, in December and re-install in May. We have members that use the cabin sometimes in January or even February and they use the lights etc. If I were to remove the batteries as recommended I would soon be told to replace them with the old AGM's.

So, can I store them in very cold weather without hurting them or not? I know they should never be charged at these temperatures and that is not problem with the right BMS. I am strictly/asking about cold storage and potential damage to the cells.

Appreciate any experience anyone might have in this regard or any scientific papers that might address this issue.

I am aware of different heating elements etc. but I am not too thrilled about leaving any "heating" device for months at a time in a location that is not monitored frequently.

I’m looking for the same answers for the same reason, just a couple hundred miles further north. I’ve contacted Epoch batteries and they say if you use their battery and use it from time to time it will work fine, but if the temp is going to stay well below zero for extended periods and you don’t use it, they would then not recommend it. Their batteries have built in heaters, but we go weeks without seeing the sun after hunting season is over. Let me know if you learn more.

 

[Daddy Tanuki]

I’m looking for the same answers for the same reason, just a couple hundred miles further north. I’ve contacted Epoch batteries and they say if you use their battery and use it from time to time it will work fine, but if the temp is going to stay well below zero for extended periods and you don’t use it, they would then not recommend it. Their batteries have built in heaters, but we go weeks without seeing the sun after hunting season is over. Let me know if you learn more.

if you shut the system down entirely including any internal heaters the batteries themselves are fine as long as no charging or discharging is going on.
You would need to warm them up to above freezing prior to charging them but cold temps just slow the calendar ageing. I would build a battery heater using any of the many systems that have been explained on the forum and simply shut everything down upon departure. (preferably with the batteries at about 60%) when you get back turn on your battery heater, clear snow off of panels and keep your SCC off until the pack has warmed up.

if you want to keep the system up and running you will need a battery warmer, a panel defrost system that heats the panels to get snow to fall off and a way to control this all. if you are skilled with circuit design and possibly one of the home brew andurino's or whatever is the current rage I am sure you can build a system that does all the above. but I would want to be able to remotely access it so that I could shut systems down if necessary before an issue occurs.

 

[SunDave]

I know this is like the pencil vs. pen joke for space travel, but regarding the panels and snow for an unattended system, it would be worth the effort to install them vertically. Other systems to clear snow are less effective and require more engineering.

 

[mvonw]

I have stored two of the larger Bluetti devices at my cabin for 4 years. It has gotten as low as -30F a few times and these still function as new. (My main battery bank is in a well insulated and heated sarcophagus I made, so they stay at a constant 60F)

 

[tucknutz]

UPDATE:
My son unexpectedly went up to the cabin last night and he sent me a screen shot of the cell voltages. These values are after the battery sat dormant for 126 days, several of which when the temperature was well below freezing, at 55% SOC with all loads disconnected except the Overkill BMS and Victron Smart Shunt. I confirmed that both of these components have very low power consumption when asleep and, according to my calculations, would have consumed less than 10 amps total over the dormant time period.

The question I did not know was what effect the low temperatures would have and how much natural self-discharge (expected very little but did not know for sure) would take place.

Since the Smart Shunt will not register very small current draws (mA) I knew whatever SOC it showed after the dormant period would likely be inaccurate. So, all I had to go by was individual cell voltages which, as you know is not a good indicator of SOC but would give me information if the end voltages were below 3.0V/cell.

The cell voltages were all around 3.28 with a delta of .004v when the dormant period began. The screen shot my son sent me last night revealed absolutely no change in either of those parameters. I am not going to try and talk him through a "controlled" charging process where one could assess how many amps it would take to fully re-charge the battery thus giving me data to calculate what the actual SOC was following the dormant period. Therefore, I cannot say with any certainty how much SOC the battery lost during the dormant period but I learned that the cells survived the winter just fine the way I stored them. I could not be happier.

Thanks to many who commented on the DIY Solar Power Forum, especially upnorthandpersonal and Curiouscarbon, for all their input when I tried to gather data on how LifePO4 cells would react to cold, no load storage. Most of the comments lead me to believe the battery would be fine as long as I disconnected the loads and solar panels and left the battery in a SOC of roughly 50%. That is what I did and, apparently, all is well.

Thank you so much for this thread and your experience! What batteries did you end up going with for this experiment?