Cold storage of LiFePO4 batteries

[REO]

I am concerned about the proper way to store LiFePO4 batteries in very cold conditions. I am not asking about charge and discharge, just storage. My boat is stored in a shop that is exposed to temperatures below zero. I spoke to a rep. at LiTime and she said the batteries should not be stored below zero. I do not have the self heating batteries, and question if self heating would work for 8 months of very cold weather if I did have that feature. This winter I devised a thermostat controlled light bulb heater and small insulated enclosure, but next year, in northern Michigan, I will not have access to electricity in the storage facility. The batteries are way too heavy for me to remove them every year. Does LiTime have it wrong? Comments from anyone with actual experience storing in extreme cold will be much appreciated.

 

[Don L]

I didn't think there was a problem storing the LFPs in cold weather, just using them. Maybe the LiTime person didn't understand your question.

 

[SteveK]

I didn't think there was a problem storing the LFPs in cold weather, just using them. Maybe the LiTime person didn't understand your question.

That is what I understand as well. The reason there are heated batteries is so they maintain a temp at which charging and discharging should occur, or in some "can" occur.

 

[Frosty]

Looking up my batteries, plus checking the data sheets for a few others I have on hand (I also looked up Li Time for their 100ah model), these are the lowest recommended "storage" temperatures:

Victron = -45ºC (-49ºF)
Lithionics = -10ºC (14ºF)
Epoch = 0ºC (32ºF)
Big Battery = -5ºC (23ºF)
SFK = No spec I could find
Li Time = -10ºC (14ºF)

Interesting. I have to wonder about some of the ratings. I mean, 32ºF (Epoch)? Come on that's just a chilly fall night.

While I'm glad to have the leeway, I kind of hope my batteries never see -49ºF
----------------------------------

PS: I would think the self-heating function is for charging, as mentioned above -- not for storage. Typically, LFP cannot be charged below freezing (or even a little above, to be on the safe side), although they can be discharged - used to power loads - without damage.

I don't have heated batteries. They do cut off their allow-to-charge circuit below 41ºF (which I could set to a lower temp if desired). This is fine for my usage as I don't need them to charge below that temperature, and heating coils (or wires) make me a little nervous. (I'm sure they're fine though.)

If I change my habits, I could heat them externally.

 

[SteveK]

@Frosty are these storage or charging specs?

 

[Frosty]

@Frosty are these storage or charging specs?

I thought the question was about cold storage, so those are the specs I posted. Lowest storage temperature. I'll go back and clarify that though.

The batteries all listed a storage temperature range (except I couldn't find one for SFK). I left off the "hot" end since the thread query was about cold storage.

 

[SteveK]

Yes I expected storage but as you pointed out 0* for Epoch seems odd for storage.
I found Epoch saying store at 20-50C and also 32-77F
so what is correct?

 

[Frosty]

Makes you wonder who has actually tested and who perhaps just threw a spec out there, doesn't it?

Also, these can change. (Whether that reflects an actual change in the battery or more specific testing, who knows.) For example the Lithionics used to be chargeable only to 113ºF. That sounds ample until you think of the batteries perhaps being in a warm bay on an also "warm" day. Later that spec was changed to 130ºF by Lithionics.

A couple of the data sheets I had on hand were from a year or two ago (although I went to Li-Time's website just this morning).

Still, the range is interesting and perhaps a bit puzzling.

 

[Frosty]

I went to Epoch's site to see if anything had changed from when I saved the data sheets.

460ah Essentials Series (doesn't have the bells and whistles/Victron comms):
Storage cold temp spec: 0ºC (32ºF)

460 Elite Series V2 (newest one):
Storage cold temp spec: 0ºC (32ºF)

So doesn't look like anything has changed there. The Elite V2 just came out this winter, too.

Oddly, you can discharge to -20ºC (-4ºF). You can also charge to those same parameters (battery is heated).

 

[Frosty]

Thinking about this, it would seem to indicate (by Victron's spec) that there is nothing about LFP cells that precludes cold storage (-49ºF). So it must either be something in the built-in BMS of internal-BMS batteries -- or just a lack of testing/confidence?

********************
Note: Victron batteries do not have a built in BMS, though that said there is nothing in the (separate) BMS spec sheet that indicates any storage temperature limits.

"Operating temperature" for the Small BMS is 0º - 120ºF. There is no storage temp limit.

They have a variety of BMS options though. That said, for long term storage you likely would not have the BMS connected at all -- I have a Victron battery in long term storage now and what I did was charge it up to full -- so it would go through its full balance cycle -- then draw it immediately back down to 75% SOC. There is nothing connected to the battery now (no BMS).

But of course you can't really do that with batteries that have a built in BMS. One thing I'm not sure of: Some of these batteries have an "Off" switch on the battery. What does that do to the BMS? Does it stay on? Or is it turned off when the switch is off?

 

[CharlieO.]

Vatrer specs. I remove my battery and take it home during winter lay-up. This is the first year I didn't take my sealed LA batteries home.

 

[tpbrady]

I would think the cold storage limit would be dictated by thermal contraction of the material used to make the battery. Electronics has cold storage limits below which there is a risk of circuit boards cracking. My guess is the data on storage temperature is based on a best guess since they haven’t been tested down to the point where a failure would occur. In my 50 years of working with telecommunications networks, most in Alaska, I have seen only one cold related failure where a production run of solid state switches failed at -32F. Once they warmed up they started working again. Turns out they were not tested below -20F.

Unfortunately the only way to find out is to try it.

Tom

 

[SteveK]

I went to Epoch's site to see if anything had changed from when I saved the data sheets.

460ah Essentials Series (doesn't have the bells and whistles/Victron comms):
Storage cold temp spec: 0ºC (32ºF)

460 Elite Series V2 (newest one):
Storage cold temp spec: 0ºC (32ºF)

So doesn't look like anything has changed there. The Elite V2 just came out this winter, too.

Oddly, you can discharge to -20ºC (-4ºF). You can also charge to those same parameters (battery is heated).

well I did a bunch of reading and the general consensus appears to be is store the batteries where you live, actually the wordings of temp range suggested is within where we have our home temps. If we are cold we turn on the heat, if we are hot we turn on the AC/fans.
The storage temp range is all over the place.
In my case where the boat lives, moored the low/high temps are within the storage range suggested on average. Above freezing, below boiling.

Up until now I was aware of do not charge below freezing or extreme heat.

 

[Frosty]

Up until now I was aware of do not charge below freezing or extreme heat.

The heat part is I think mostly (all?) a function of it's just hard on the batteries. Reduces lifespan, etc. I mean obviously this doesn't apply if it's 200ºF, but I mean if it's just "hot." Even just storing or using the batteries in extreme heat is hard on them. But then it's not a good thing for any type of battery, AFAIK.

Charging below freezing I am led to believe can be a more instantly damaging effect. But there are typically safeguards built in or available. Ones I know of:

1) Allow-to-charge signal in BMS (cuts off charge section of BMS/battery if below a certain temp).

2) Relay in BMV 700/712 (if combined with temp sensor can cut off charging below a set temp)

3) Heating built into battery (allows charge to continue as long as heating is keeping battery above no-go temp)

4) External heating mat (simlar to #3 but on outside of battery)

5) And of course there is simply heating the area (room/compartment) where the batteries are.

A factor on boats in the water is that the area below the waterline may stay a bit warmer. I have been cruising when overnight lows were in the low 30's but my house bank didn't get cold enough to cut off charging (I have that set at 41ºF). My batteries sit close to the hull below the waterline.

Of course out of the water that doesn't help at all.

At least they are lighter if you have to hump them off the boat for the winter. Mine are 200ah and 45# apiece. (Though the big ones like the Epoch 460 are nearly 100#.)

I still wouldn't be pleased if the stated low temp storage for mine was 32ºF. Come on, they shouldn't be as weak as lettuce.

 

[REO]

So, it seems like nobody knows if temperatures below zero will harm the batteries. Some manufacturers say yes, some say no. I feel like I have good information for charging and discharging. Manufacturers seem to, more or less, agree. But why so much variation on storage temperature? I feel like they all get the key components from the same place why not test and set a standard. Interesting that we have yet to get a response from someone who has stored the batteries at below freezing....Nobody from Michigan stores their boat in an unheated shop???

 

[Frosty]

But why so much variation on storage temperature? I feel like they all get the key components from the same place why not test and set a standard.

I hear you. That makes me wonder if it is some component of the BMS? Or as you say, just "Well we haven't tested so let's slap a number on it." I find that so aggravating. In fact I eschewed several batteries just based on poor/missing (or not robust enough) specs. Same thing when buying AGM: Went with Lifeline in good part because they had great documentation and knowledgeable people on their tech line. But I pay more with that method.

Perhaps it's somewhat just par for the course with the super budget batteries (Li-Time, etc.). Testing costs money and they seem to be going for low price. I guess the price allows one to buy another if one is damaged, but that's annoying!

I have not checked recently but Victron used to use (and may still use) Winston cells. I don't know about the others on the list. I didn't put Battleborn on the list because they have a different shaped type of cell (forget what you call it, but they are cylindrical).

 

[tiltrider1]

Part of the problem is the data we get from the RV people. A lot of high tech RV’s were sold with LFP batteries with built in heaters. Some are seeing battery failures at the 5 year mark.

When you ask them what they did to winterize their set up you get answers like, I turned off the battery heater but I left the solar panel on so the battery wouldn’t go dead.


Does that mean the solar panel damaged the battery on a sunny 10 degree day? Maybe the battery didn’t need a charge that day? Did the week long cold snap of single digit temperatures kill the battery. Did something else kill the battery? Did they leave a light on and that snowy week allowed the batteries to get fully drained?

Even when we get information it’s usually too incomplete to draw any useful conclusions. Time will eventually give us the answers. Fortunately my batteries never see low temperatures.

 

[Mambo42]

The use of LiFePO4 in cold temperatures is not the problem, the charging however is. My BMS won't allow charging below 5 Celsius, but usage is not a problem.
So if you just want to store your batteries, but not use them, there is really no problem. If you really want to make sure the batteries are not discharging you can completely disconnect the batteries from the complete system. That can either be done via the BMS or by disconnecting the actual leads to the batteries.
This winter my boat was stored in a location where it was below 5 Celsius. I had no problem using the batteries for basically anything, I just could not charge them, the BMS prohibited that. I could have gone into the settings of the BMS and change that temperature, but I did not see a need for that.
Long term storage at a low temperature does not really do a lot for the battery, I did not see the percentage of charge going down.

 

[Frosty]

So if you just want to store your batteries, but not use them, there is really no problem.

I think where the OP and others have a "problem" is that their battery mfgr's are specifically saying NOT to store the battery below various seemingly benign temperatures (such as 0ºC/32ºF). See list in post #4 above.

Those temp limits for *storing* the battery seem ridiculous to me; but if I had one of those brand batteries it would make me a bit uncomfortable. Is it real? Are they pulling numbers out of a hat? Why are they SO limiting?

The Victron batteries cost more, and you have to figure out how to organize and tidy some extra wires (because external BMS), but I'm glad I have them (I bought them for other spec reasons but they are rated to store in very cold temps).

But I can see why everyone wouldn't want them.

It's just infuriating because..... are those sad specs even real? Okay Li-Time fair enough, they are super budget and I would barely trust any of their numbers anyway (for good or bad). But Epoch? They are placing themselves as a "better" mfgr. Yet now you may have to hump your 94# Elite 460's on and off the boat for even late fall storage (much less winter).

 

[Barking Sands]

The problem is the definition of "storage".
Warehouse for long periods?
A few weeks in the hard?
Several years?

See this spec sheet from Eve cells

EVE LF105 3.2V 105Ah LiFePO4 Battery Cell

LF105 3.2V 105Ah LiFePO4 Lithium Battery Rechargeable lifepo4 prismatic Cells

www.evlithium.com

and another EVE spec sheet

https://www.gobelpower.com/download/EVE-LF105-LiFePO4-Battery-Cell-Product-Specification-20191202.pdf

They list 2 criteria
1 month -20C to 45c
1 Year 0c to 35c

So it is more of a continuum. You might even be able to extrapolate lower temps for shorter durations.

The Winston cells, which I think the older Victron batteries used list -20c to 60c for storage. Is that long term? Not sure.

https://thundersky-winston.com/static/upload/file/20240819/1724058901707155.pdf

Supposedly the new Victron NG have Vision cells. Not much detail but I did find this if its the same cells.

Vision 3.2V 100Ah Rechargeable LiFePO LiFePO4 Battery Cell

This is the Vision 100Ah battery, brand new A-grade, with an internal resistance of less than 0.25 ohms. It can cycle up to 4500 times and comes with an original QR code. The charging rate is 1C and the discharging rate is 3C. It weighs around 1.9kg and comes with M4 screws and connectors.

ubppower.com

Same storage criteria:
Short Term Storage Temperature
-20℃~45℃
Long Term Storage Temperature
0℃~35℃

Epoch was born out of the 18650 store that has sold various cells for a very long time. So obviously they are using cell data since most of their batteries use EVE cells.

IMO you guys that live in very cold climates must come up with a way to maintain a decent temperature such as a lightbulb heater. One thing I have noticed has been the temp stability in daily fluctuations. Monitoring the 460 Epoch via VRM shows quite the dampening effect of that mass, especially considering its against the hull. Granted that wont help with multiple days of very cold weather, especially if on the hard.

 

[Mambo42]

I was googling for some explanation of long term cold storage of LiFePO4 batteries, found the following

Cold temperatures stop the battery’s internal chemistries, increasing battery health. Therefore, keeping the battery in freezing temperatures is a good thing for preserving its health in long-term storage.

and also

For LiFePO4 batteries, the temperature range depends on the storage time. Generally speaking, follow the guidelines below:

• Less than 30 days: -20℃ to 60℃
• Between 30 and 90 days: -10℃ to 35℃
• More than 90 days: 15℃ to 35 ℃

Storing LiFePO4 Batteries in Cold Weather (Winter)​

Low temperature is not an issue for lithium batteries since it leads to slower chemical reactions inside the battery, increasing its life. However, while the battery chemistry enhances in cold weather, extremely cold temperatures may cause some battery components to crack (such as its plastic casing). Therefore, it is a good idea to store lithium batteries indoors and avoid extremely cold temperatures

I don't know how cold it gets in the area of OP, but I should not worry about it too much. That is of course unless you want to start charging the batteries, because that will be impossible.

 

[Mambo42]

I think where the OP and others have a "problem" is that their battery mfgr's are specifically saying NOT to store the battery below various seemingly benign temperatures (such as 0ºC/32ºF). See list in post #4 above.

Those temp limits for *storing* the battery seem ridiculous to me; but if I had one of those brand batteries it would make me a bit uncomfortable. Is it real? Are they pulling numbers out of a hat? Why are they SO limiting?

The Victron batteries cost more, and you have to figure out how to organize and tidy some extra wires (because external BMS), but I'm glad I have them (I bought them for other spec reasons but they are rated to store in very cold temps).

But I can see why everyone wouldn't want them.

It's just infuriating because..... are those sad specs even real? Okay Li-Time fair enough, they are super budget and I would barely trust any of their numbers anyway (for good or bad). But Epoch? They are placing themselves as a "better" mfgr. Yet now you may have to hump your 94# Elite 460's on and off the boat for even late fall storage (much less winter).

Using LiFePO4 in cold temperatures in itself is not really a problem. You can buy the ones with internal heating or, if you don't want to have the internal heating, you can always use a heating blanket or panels between the batteries. They will draw electricity, but since you are using the batteries anyway you can then also charge them normally.
In itself the colder temperatures are no big surprise, since also AGM and other batteries don't perform too well in low temperatures.

 

[Frosty]

Using LiFePO4 in cold temperatures in itself is not really a problem. You can buy the ones with internal heating or, if you don't want to have the internal heating, you can always use a heating blanket or panels between the batteries.

Understood. But this thread is about *storage* of LFP batteries and how some mfgrs spec some pretty "warm" limits on how cold that can be. e.g: 0ºC (32ºF).

 

[Frosty]

One thing I have noticed has been the temp stability in daily fluctuations. Monitoring the 460 Epoch via VRM shows quite the dampening effect of that mass, especially considering its against the hull. Granted that wont help with multiple days of very cold weather, especially if on the hard.

Agreed on that. I was in the water over several nights that were down in the low 30's, and my house bank stayed well over 40ºF (no heat running on the boat).

On land (hull exposed to air) and as soon as it got down around 30º I got a "not allowed to charge" warning (which is fine, as that's how my system is supposed to work). Once temps warmed up, so did the batteries and the warning was removed.

Of course many people will be storing their boats on the hard in the fall or winter months.

*******

Interesting data you posted on the duration and storage temps. It's too bad the mfgrs don't share more of that type of data. As you say "how long is long?" Well, would it be that difficult to add that info?

Many already specify various charging schemes for storage of <3 months, 6 months, >6 months, etc. So the granularity is there. Why not add the same data for storage? I think it's pretty obvious that when two of your primary markets are marine and RV use, that people will be storing things during "off" seasons.

*********

A bit off-topic but I was interested in what you said about Victron cells. I had "heard" that they stopped using Winston cells and wondered when (I have three Victron batteries that are different ages -- not all in the same system). Sounds like the change was when they introduced the NG models?

 

[CharlieO.]

The info from my Vatrer battery manual is a little different from the previous information I posted from the Vatrer website.

 

[REO]

This has been an extremely informative and interesting discussion. I am surprised that the topic has not come up before. I got the answer I was looking for, although I was hoping for a different result. Storing LFP batteries for 8 months in weather that includes temperatures below -10 degrees F is a very bad idea. I was surprised that no one from the frozen north commented, but I guess they were smart enough to avoid LFP if they had to store in an unheated environment.

 

[CharlieO.]

This has been an extremely informative and interesting discussion. I am surprised that the topic has not come up before. I got the answer I was looking for, although I was hoping for a different result. Storing LFP batteries for 8 months in weather that includes temperatures below -10 degrees F is a very bad idea. I was surprised that no one from the frozen north commented, but I guess they were smart enough to avoid LFP if they had to store in an unheated environment.

For me the benefits of the LiFePo4 are worth me taking the batteries home during winter layup.

 

[REO]

I installed two 300 ah batteries in a hard to access area. Should have got smaller batteries. Hindsight is 20/20. I am going to move to a storage spot with electricity next winter. My thermostat and light bulb heater worked in Northwest Arkansas. Just have to use bigger bulbs in Michigan.

 

[CaptTom]

I was surprised that no one from the frozen north commented, but I guess they were smart enough to avoid LFP if they had to store in an unheated environment.

I've been following this closely. We've had -40F days here before, and most winters I store on land. I've just assumed this would be a show-stopper for me switching to LiFPO batteries. This thread seems to confirm that.

 

[Frosty]

I've been following this closely. We've had -40F days here before, and most winters I store on land. I've just assumed this would be a show-stopper for me switching to LiFPO batteries. This thread seems to confirm that.

Well there are the Victron batteries that can be stored down to -45º F.

They are more expensive than something like LiTime, and (for better or worse) you do have to run/tidy the BMS wires (external BMS). They are only ~16 AWG though. And you do have a bit more control.

I originally went for them because I could get 200ah in a battery case close in size (even a bit smaller) than a Group 27. I had space constraints. The extra stuff that has to do with the external BMS I could find space for easier than a big square box (battery).