This winter I was riding my bike at -6°C (21.2°F) with my phone mounted on the handlebar. After about half an hour of riding, I stopped to take a picture with it.
The picture alone made the battery drop by around 3%, and after a minute I turned the screen on again for a very short time, afterwards the battery dropped from 80% to 8% in less than 5 minutes.
I had this phone on my handlebar for a couple of times at down to -7°C (19.4°F), as well as another one (I have my daily driver mounted for podcasts and photos and another cheap one as a Garmin replacement for tracking) and had never seen this before nor afterwards.
The difference is that your phone does not have thermal management for its battery, other than passive cooling. EV batteries, on the other hand, do actively manage their temperature; even a parked EV might, if the environment is too cold, use up a bit of its stored power to heat up the battery to keep it in the correct temperature range.
The picture alone made the battery drop by around 3%, and after a minute I turned the screen on again for a very short time, afterwards the battery dropped from 80% to 8% in less than 5 minutes.
I had this phone on my handlebar for a couple of times at down to -7°C (19.4°F), as well as another one (I have my daily driver mounted for podcasts and photos and another cheap one as a Garmin replacement for tracking) and had never seen this before nor afterwards.