is it safe to store lipos at -10°C ?

[izeman]

subject says all. just before i left for vacation i read one of those lipo-fire thread and was scared again. so i moved all my lipos packs (about 10x 6s 5000) into the fire place to be 100% safe. but this of course is no full time solution. even in a fire proof metal box there will be a lot of smoke. so if i store them in the cellar a one battery explodes, there will be a lot of restauration afterwards.

so i may put the box in the wooden garden shed. but this is not heated of couse. but some smoke wouldn't do any harm there. at the moment we have nearly -20°C (-4F). is it safe for the lipos? of course they are charged to 3.8v and i don't intend to use them until it gets warmer again in spring.

 

[Arlo1]

Below 0 deg C is not good for them. If I was you I would just put them in an ammo box or something metal and make sure it will shield most or all the flames if they were to ignite and put them somewhere >0 and < 30 deg C I actualy just have some of mine in a plastic cooler for now but thats cause I may need acsess to them and need them wired in series they way I have them. I just wanted them protected from flying drebis and the cats. I would not recomend what I do to anyone.

 

[izeman]

hmmm. what does "not good" mean exactly? i know that all batteries will deliver less power when they are cold. but i will not use them at those temp. will they take permanent damage? will the loose some charge cycles? will their capacity drop one the are "warm" again? some of that things do matter to me, some don't (eg.life span)

 

[el_walto]

I've stored my LiFePo4 outside for a few years. They still work, that's the only evidence i have. -20C at times. I was even still using them to power my bike at -20C. Basically you are just going to get a bunch of peoples opinions because i dont' know if anyone has actually published a test related to storing lipo at -10C

 

[izeman]

you're probably right. maybe i'll find some scientific research on that topic. there must be some. just because someone surely tested lipo in cars or similar. even though they mostly use li-ion (or any other chemistry and not lipo )

 

[Arlo1]

I've stored my LiFePo4 outside for a few years. They still work, that's the only evidence i have. -20C at times. I was even still using them to power my bike at -20C. Basically you are just going to get a bunch of peoples opinions because i dont' know if anyone has actually published a test related to storing lipo at -10C

I asked Luke (battery engineer) the lowest safe temp to store lipo at and he said "0 deg C" im guessing it is probably because it has something that freezes at 0 deg C inside it causing damage.
If you want to know more keep digging and read the two lipo safety threads.

 

[izeman]

thx. that sounds reasonable. freezing some fluid inside will not be good.

 

[Ziggurat]

A couple of quotes about LiPo and low temperatures:

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=23361&p=347200#p347200

The big danger with cold batteries is charging them cold. Discharging cold is OK, performance sucks, but nothing is damaged. Charging cold is damaging to the batteries. You should also strongly avoid going to 4.2v on a cold battery, as it starts forming metalic Li deposits and rapidly degrading the safety and cycle life. If it was below freezing out and i had to charge, I would set HVC for like 4.05v at the most.

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9170&p=181974#p181974

If you plan to keep them stored for an extended period, drop to about 3.8-3.9v, then throw them in the freezer. The temp change will drop the resting voltage to nominal, and the chart I saw for some LiCo polymer cells at 28degF showed something like 12 years shelf-life to 80% capacity. It was 3 years at 70degF.

The freezer quote is from 2009. I suppose the newer LiPo could be different in cold tolerance. And he quotes 28 F, just below 0 C, while freezers are more like -15 to -20 C.

 

[Arlo1]

Weird. Ill send him a mesage!

 

[izeman]

i googled freezer and lipo and found that:

http://www.kongpower.com/faq_en/show.asp?MsgID=14&page=1&srhTxt01=&srhTxt02

they recommend storage in a freezer!

 

[BatteryMooch]

My understanding of the situation is that putting LiPo's (or any cell) in a freezer isn't a problem as long as the electrolyte doesn't freeze. If it does, it can form ice crystals that can distort the cell internally (causing any number of problems) and/or puncture the separator (increasing internal leakage or causing shorts that will damage the separator even more and perhaps induce thermal runaway).

Without knowing at what temp the electrolyte in your cell freezes at, I'm not sure anyone can say if it's safe or not?

 

[Arlo1]

I got a quick message back from luke. And he said "0degC should virtually stop the whole decay process. " So I guess cool is good im not sure if -10 deg C is good.

 

[jonescg]

On a similar note, is it OK to store LiPo at +45'C? Cause that's what my shed gets up to almost every single day of February. Hope it's OK...

 

[izeman]

On a similar note, is it OK to store LiPo at +45'C? Cause that's what my shed gets up to almost every single day of February. Hope it's OK...

oh man! you're on the WRONG SIDE OF THE EARTH. february is F*** COLD !!
but to be honest i can't say what i dislike more -20°C or +45°C. both is not good for biking *ggg*

 

[dogman dan]

45c is hotter than ambient I take it? At least try to ventilate the shed so you aren't parking your batts in a sweatbox.

Pesky real world. So hard to try to do all your storing at low temp, yet do all your discharging and charging at air conditioned room temperature. What are you going to do, watch the weather for the one day you can ride.

Whatever happens to the batts, not much you can do but live with it, or build an air conditioned garage.

 

[Ziggurat]

There's a great link that zombiess posted a few months back:

http://www.mpoweruk.com/lithium_failures.htm

Has lots of detailed technical information about temperature effects on the lithium battery family, during charge or discharge.

I just found this on the same site: http://www.mpoweruk.com/storage.htm

The possible storage temperature range for Lithium-Ion batteries is is -20°C to 60°C but for prolonged storage period -20°C to 25°C is recommended and 15°C is ideal. Cells should be stored with a partial charge of between 30% and 50%.

 

[grindz145]

-10 is no big deal. Even down to -20 or -30 isn't terrible. However, when you get much lower than that the separator can break down and you get into big trouble. I wouldn't be terrible concerned about -10. That comes from several years of testing 18650s, but the lipos will be similar.