I live in the polar vortex and so walking outside I’ve had a full phone battery go dead in under twenty minutes. We’re talking idk ≈ -40F. When it’s warmed up again there it is suddenly at 60%. I don’t expect to understand well because I know little about batteries, but what’s the deal? And how is it that once it’s warmed it is not only fully functional but has retained charge? At what temperature does this effect begin to take hold?
In: Technology
The battery is not empty, but the capacity cannot be fully utilized because the cold increases the resistance of the cells which decreases the current up to a point where the phone can no longer be used.
The capacity you see is calculated by means of software or dedicated chips and these contain algorithms to decrease the displayed capacity value at lower temperatures to be aligned with this behavior. When the temperature rises this so called state of charge gets calculated higher again.
The temperature limits depend on the cell chemistry. But for LiPo cells, this effect can already be noticed above the freezing point and things start getting really bad below -20 °C. Charging is worse, charging a battery below freezing point is often considered to be damaging.
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