Safe battery use in the cold

uPET

10 mW
Joined
May 28, 2021
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The outdoor temps are sub zero all day long at the moment. It's not easy for me to take the battery off the bike when I get to work and it stands all day outside, so even though the bike is stored in the warm over night and recharged above freezing, the trip home is with a sub zero battery. Has anyone got any info on how damaging this is for the battery? Is there a temp you must not go below for safe use of lithium batteries (not including charging - which must be done above zero).
 
-20 to 55 °C is the discharge temperature minimum ( operation) temps of a NMC battery.

-20C... ( -4F) ... you can discharge most lithium cell battery chemistry type WELL BELOW freezing with zero detriment.




-0 to 55 °C is the Charging temps of a NMC battery.

https://batteryuniversity.com/article/bu-502-discharging-at-high-and-low-temperatures

https://iopscience.iop.org/article/10.1088/1757-899X/211/1/012005/pdf
 

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There are (a) theoretical temp ranges for different chemistries, (b) there are temp ranges for specific cells, (c) and then there are temp ranges for complete assembled batteries units.

Thermal cycling (going from cold to warm, and back) can potentially cause physical stress and damage, and condensation. How much? The manufacturer of the complete battery unit should test and make some predictions. I doubt any ever did.

If it's difficult to remove, why not make it easy to remove? :lol:
 
DogDipstick said:
-20 to 55 °C is the discharge temperature minimum ( operation) temps of a NMC battery.

-20C... ( -4F) ... you can discharge most lithium cell battery chemistry type WELL BELOW freezing with zero detriment.




-0 to 55 °C is the Charging temps of a NMC battery.

https://batteryuniversity.com/article/bu-502-discharging-at-high-and-low-temperatures

https://iopscience.iop.org/article/10.1088/1757-899X/211/1/012005/pdf

Thanks! That's really useful info. So no need to worry until it gets close to -20C
 
Comrade said:
There are (a) theoretical temp ranges for different chemistries, (b) there are temp ranges for specific cells, (c) and then there are temp ranges for complete assembled batteries units.

Thermal cycling (going from cold to warm, and back) can potentially cause physical stress and damage, and condensation. How much? The manufacturer of the complete battery unit should test and make some predictions. I doubt any ever did.

If it's difficult to remove, why not make it easy to remove? :lol:

I put my bike into a warm place when I get home, but not too warm then give it a couple of hours before I re-charge.

Yes, would like to make it easier to remove, but that means designing and making a new mounting system - which I should of done during the summer when the weather was warmer :)
 
You might get significantly less range with a freezing cold battery. If your pack is oversized enough, it should be no problem.
 
Is it common for a BMS to not allow charging below a certain temperature? I discovered yesterday that my em3ev battery would not charge when it was stored at around 10 degrees Celsius. Or actually first I was puzzled why it would not start charging, and it took me a while to realize it was because of the temperature and that charging works normally after I bring the battery inside to warm a bit.
 
ilu said:
Is it common for a BMS to not allow charging below a certain temperature?

If it's a good BMS, of course. If you charge a li-on cell to 4.2V in the cold, you'll find it overcharged when it warms up.
 
A em3ev battery ask Paul or employees of. I'm curious what type of guidelines that they would give you on charging discharging recharging or I believe a heat wrap with it's own battery could help.
DrAngle has a tread I think it has a small heater blanket ? Not shear but there is a thread here.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=47924#p704497
 
I'm trying to figure out why the chart above shows LFP (also known as LiFePO?) shows charging down to -20 when everything I've ever read says you cannot charge them below freezing. ???? What don't I understand?
 
Diggs said:
I'm trying to figure out why the chart above shows LFP (also known as LiFePO?) shows charging down to -20 when everything I've ever read says you cannot charge them below freezing. ???? What don't I understand?

LFP is hardier at colder temps than Li-ion, for sure, but not immune. The confusion is coming from the fact that there's an acceptable range, not a hard and fast limit to low temp cutoff. More importantly, manufacturers vary; some higher quality LFP cells can charge and discharge and lower temps than others. This is why it's recommended to check the spec sheet for different batteries that you're planning on using.
 
fechter said:
You might get significantly less range with a freezing cold battery. If your pack is oversized enough, it should be no problem.

My newest winter use pack is a 36V 20Ah 21700 50E. It does have reduced range and power. more like a 8-10Ah pack in Minnesota winters. Some of us use clothing warmers to keep battery temps up.
 

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ilu said:
Is it common for a BMS to not allow charging below a certain temperature?

I've not seen a low temp switch in any of the BMS I use. I'm just starting to want the high temperature cutoffs in a BMS. I think that as we move toward UL certification of batteries that both a freeze limit for charge, and over temp inhibit for discharge will be a requirement.
 
Spec sheets only show the extreme edge case causing immediately apparent DAMAGE.

Trying to get good lifespan means completely different care parameters far from ever approaching those extremes.

The key with charging as temps get below T-shirt weather, is DRASTICALLY reduced C-rate levels.

For really fast charging, best to get the cells very hot first.

If 1C is OK at 77°F then as you get down below 50° keep it well below 0.5C

More like 0.1C as you get anywhere near freezing

Charging AT ALL below freezing temps, all bets are off you're on your own, likely drastically reducing cycle lifespan.

And yes just as true for Winstons, never mind what the data sheet says.

LTO is the only LI chemistry which is radically more tolerant, but only generalisations are available not quantified testing.

Keep your cells warm folks
 
john61ct said:
More like 0.1C as you get anywhere near freezing

Charging AT ALL below freezing temps, all bets are off you're on your own, likely drastically reducing cycle lifespan.

Lol My experiences differ. Charge every day at greater than those (0.5C? i'll be here all day) rates. Not a bit of lost capacity. Charging cells right now at 1C in the cold on datalog. Its like... 36* here outside. Colder int eh sheltered cold garage. Yes, power may be quartered or halved.. but y bike is damn powerful anyway and took me 9 miles in 12 min in 28* weather of the night last night.

i'll see you in ten years and tell you how i did.
 
docw009 said:
ilu said:
Is it common for a BMS to not allow charging below a certain temperature?

I've not seen a low temp switch in any of the BMS I use.

Very common and on all the BMS I have ever used. Certainly.

For example.. this JBD blutoof bms holds three temp sensors.. two external ad one internal tothe board... and if the temp goes under THIS setting, all current flow is broken and the pack is open. In or out.

Low temp protection. Certainly all BMS have it in the architecture... whether they use it is another matter ( in teh programmed software, as programmed by the OEm)
 

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