FAQ: Low temperature operation: What is the capacity of the LiFePO4 battery at different temperatures? (at 25°C, at 0°C, at -20°C ?)

1) Battery capacity

For 10*C to 40*C the battery nominal capacity is 100%. For temperatures bellow 10*C the internal resistance of the battery increases and as a result the total capacity decreases. The information is published here at GWL/Blog.

at 0°C: we estimate some 90% of available capacity.
at -20°C: we estimate some 60% of available capacity.

2) Low voltage disconnect (under load)

The discharge voltage level changes (from suggested 2.8V) with the change of temperature.

The information is published here at GWL/Blog:

at 0°C: the low voltage level changes from 2.8V to 2.4V
at -20°C: the low voltage level changes from 2.8V to 2.0V

3) Battery operating temperature

We do not recommend to leave the battery unattended to become frozen to low temperatures. In cold climates, we suggest to make sure the temperature of the battery pack will stay at least at +5*C (or more).

We do not recommend operating the battery in bellow zero temperatures.

4) Some tips to operate the battery in cold climate

a) Make proper insulation of the pack so that the pack does not lose temperature to outside cold environment

b) Arrange for the pack heating (during charge). Properly insulated pack may be preheated to quite high temperature (even to 30*C) to absorb the thermal energy. This way the properly insulated pack of large capacity may stay warm for several days.

c) Arrange for the pack “defrosting”. Properly insulated pack may use some part of its energy to warm itself before or at the beginning of the operation in cold climate. Usually about 5% to 8% od energy may be used to increase the temperature of the properly insulated battery pack.