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According to this site, you can store in -40°C/-40°F just never charge them below freezing.

I have a E-Bike in cold Canada and taking the battery out is a pain. The link says just make sure it's disconnected with a 50%-60% charge.

I cannot get answer on the internet. They just keep saying do not use in cold weather ONLY. I just want to store in cold, not use the battery.

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    \$\begingroup\$ check the manufacturer datasheet \$\endgroup\$
    – jsotola
    Nov 24, 2020 at 18:20
  • \$\begingroup\$ That is, the manufacturer of the cells, not the pack or bike. If you can't find a datasheet for those brand cells with the info you want, ask that cell manufacturer directly. \$\endgroup\$
    – rdtsc
    Nov 24, 2020 at 18:27
  • \$\begingroup\$ How cold is cold? There's a difference between just being cold and freezing (of the battery, not of water). \$\endgroup\$
    – DKNguyen
    Nov 24, 2020 at 19:39
  • \$\begingroup\$ For reference, the storage temp (not operational temp) for Trojan Trillium LFP batteries is -40 to 60C. The operational temp is -20, HOWEVER, there is a note in the datasheet that charging below 23C should not be done at the full rate. trojanbattery.com/pdf/datasheets/24_Lithium_12.8-92.pdf \$\endgroup\$
    – user57037
    Nov 24, 2020 at 21:29

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Lithium batteries are powered by chemical reactions (citation needed). As a rule of thumb, every +10C doubles the reaction rate -- which means that every -10C halves the reaction rate. Charging a lithium battery is taxing on them as-is, and it is damaging if the electrolyte is operating at 1/64th of its usual performance (20C -> -40C). The specific behavior is in your manufacturer's data sheet (if one exists), but it's fairly safe to say the batteries would prefer to be about room temperature.

According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351962.pdf, the freeze point of conventional LiPo electrolyte is about -30C. You run a very serious risk of internal mechanical damage in the cell below this point. I would add 10C to this to give myself headroom.

This gives you a storage temperature of -20C to +20C at roughly 50% SoC (~ 3.8v/cell). In this range, cooler will be better. But, you cannot use the cells until their internal temperature has hit operating temperature. This may be several minutes, or even hours, after the exterior of the cells has warmed.

TLDR: your choice is to not live in Hoth, or take your battery inside.

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    \$\begingroup\$ That paper seems to be rather old and also directed at lithium ion batteries which are not the same as LiFePO4 batteries. The datasheet for Trojan Trillium LiFePO4 batteries lists a storage temp of -40 to 60C. \$\endgroup\$
    – user57037
    Nov 24, 2020 at 21:32
  • \$\begingroup\$ That seem more like it , my question link site could not be that off the mark . There is no moisture in a LifePO4 so it makes sense "cold not in use storage" should not hurt anything. \$\endgroup\$ Nov 25, 2020 at 19:53

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