Cold storage of LiFePO4 batteries

[CaptTom]

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

I saw that. But is that because it's physically or chemically a different battery construction, or is it just a more optimistic marketing department? More, and especially unbiased, data would be helpful.

 

[Frosty]

I saw that. But is that because it's physically or chemically a different battery construction, or is it just a more optimistic marketing department? More, and especially unbiased, data would be helpful.

Obviously I don't have a way to know for sure. But Victron is pretty solid. Decent warranty and the company isn't going to just disappear. (3 years which you can upgrade to 10 years). I think (?) it's possible to see how cold the battery has gotten, for proof.

One big difference is that the BMS is not inside the battery. I don't know if that makes a difference but it *is* a difference.

 

[SteveK]

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.

What protection do you have for FLA batteries? In general for the entire boat. Until reading on this forum it did not occur to me that boats are stored unheated on land, many without power to add heat.

 

[luna]

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.

Where is it that you store your boat that has an occasional ambient temperature of -40?

 

[Barking Sands]

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).

Can they though. What is the cell manufacturer? What does the cell manufacturer say?

 

[Barking Sands]

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.

I have the feeling that the storage temps quoted might be very conservative, but yea I wish there was better data.

 

[Frosty]

Can they though. What is the cell manufacturer? What does the cell manufacturer say?

Well they say so. And they warranty the batteries. I don't know what else I would go by?

I don't have cold storage temps to test them; but I guess if I did I would just make sure to store them in those temps sometime in the first three years (or the first ten years if I went for the longer warranty).

I can say they are conservative in their charging temps. Supposedly you can charge LFP down to freezing (32ºF), but they have the cutoff set at 41ºF. You CAN adjust it down lower, but at your own peril (they let you know in no uncertain terms).

There is the ability to set an offset, if you find that the battery's temperature is consistently off with reality (like a calibration of sorts). But still, once you get that set you should set the "cut-off-the-charging" temp to 41ºF.

I don't know why they would be super conservative there (since that's almost ten degrees above freezing), but then tell you to go ahead and store them at temps down to -45ºF if they thought that would wreck them (especially since if you have those temps, you are likely to also have them in the first three years, when they are under warranty and Victron would be replacing them for you).

But I don't have a lab to prove otherwise, nor storage temps of -40ºF to try it in real life.

 

[SeaGator]

I agree with most that if you are NOT using them (charging or discharging) then you are fine below freezing. I have two LiTime 460Ah non-heated batteries but do not plan on using them in freezing temps. Simple unconnected storage should be fine. Also do not store a fully charged battery.

 

[Capt Dan]

I agree with Charlie O.
The benefits of LFP are worth me schlepping my batteries to my dirt home. Why risk it? Besides, If I don’t, I might void my warranty.

Be careful about general statements like, “I don’t think I did them any harm by letting them freeze (and thaw) repeatedly. You may have unwittingly taken many cycles off your batteries, and that would be unfortunate as it would bring the long life average down. You don’t want to be the guy that had the bad experience.

Just saying…

 

[Delta Riverat]

Yeah, and it's not like they are heavy and hard to move either.

 

[Frankdog]

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.

Temp is not the problem, there is a issue with charging rates when below 5deg C, there is confusion probably with operational parameters versus storage i would say.

 

[Frosty]

Temp is not the problem, there is a issue with charging rates when below 5deg C, there is confusion probably with operational parameters versus storage i would say.

I don't think that's the case. Reason I say that is that many of the brands list a storage temperature that would be too cold for normal operation of an unheated battery; yet not as cold as you could go for operation of a heated battery. So it wouldn't make sense.

Not saying their published parameters are correct - or that there isn't bad information in them; just that it doesn't look like a simple case of confusion of operation vs. storage parameters.

 

[CharlieO.]

Temp is not the problem, there is an issue with charging rates when below 5deg C, there is confusion probably with operational parameters versus storage i would say.

The specs I posted definitely show a difference between usage and storage parameters, straight from their website and their operating manual.

 

[BDalt]

The original poster in this thread was somewhat off-base with respect to the self-heating feature on some Li batteries. I did not see a clear explanation in subsequent posts. The BMS on all self-heating and (most?) non-self heating batteries will prevent charging below temperature X. Self-heating batteries divert an applied charging current to heat the battery sufficient for safe charging to commence, then switch to charging from heating. There is no storage heating option built into the self-heater.

 

[BDalt]

WRT cold storage, the lithium battery portable car battery boosters travel in the trunk of cars here in Northern Ontaio at subzero temperature all winter, stay fully charged and boost a battery without being heated. I've gone to a Li battery ice fishing auger and that works like a charm. I charge indoors after warming to room temperature.

 

[DDW]

It would be nice if the manufacturers would clean up their data at least. For example I can find different numbers for the same Epoch battery on their webpage, spec sheet, and manual. Which is correct? Other examples have been cited above. Pick a number, and stick with it in all your literature.

I'm also a little skeptical that the battery "manufacturer" (most often just an assembler of bought in components) is much of an authority on the subject of cold weather storage. The cell manufacturer's data would be more reliable, hopefully the battery assembler is parroting that spec, but perhaps not always.