Cold Weather Lithium Ion Battery Performance

Consistent discharge behavior with a distinct acceleration in rate-of-decline at the 70% charge mark.

The good news is a 4400mAh battery can power this outdoor module for three days if sunlight for solar recharge is limited during cloudy days.

4400mAh Battery voltage at 3.74V at end of graph

Over four days from a full charge

Lithium batteries do not like to be charged at temperatures below 32 degrees. A cold-weather function has been implemented with charging disabled when the enclosure interior temperature falls below 34 degrees. While initial data suggests this is working as intended, further testing is needed to verify charging current is not supplied to the battery.

Testing outdoors has demonstrated that solar heating of the enclosure is helpful in keeping the interior temperature above air temperature, extending the cold-weather charge window significantly. Good news for the winter, no doubt a sun shield will be needed during the summer.