Winter came eventually

The temperature has been between -15..-22degC for a week now and I got the cold driving experiences I was waiting for. I installed a simple indoor/outdoor temperature sensor in the middle of my battery pack to see what happens there while driving. I learned that the temperature rise was about 15..20degC so the temperature would climb up just above 0 on a -15degC day.

With such low temperatures the battery pack was struggling to keep up the voltage during uphills and I had to be patient not to give too much throttle or the battery voltage would have dived below 50v and the BMS would have cutted off for sure. As there was less than normal power available from the batteries due to their temperature it was hard to keep up with the traffic at some points.

To improve the situation while the cold weather came here to stay, I decided to seal the engine room and insulate the battery pack as well as I could.

I used bubble wrap to insulate the battery pack. Then I blocked the airflow from the engine room using foamed plastic (the gray sheets in the pictures). I also covered the bottom of the engine room from all bigger holes.

This had a dramatic positive effect for winter driving! Today morning the outside temperature was -22degC and the battery temperature was +4degC when I started my every day work trip from garage. When I got there the battery pack temperature showed +22degC and the battery performance was close to what it was in summertime!

Another positive surprise was that when I went to lunch four hours later the pack's temperature showed still +15degC while the outside temperature was 30 degrees less!

I think the rest of the winter will be easy driving unless any super freezing days will be ahead.

Almost forgot; when I reached work the car's cabin temperature was -12degC.. To fix this I ordered a new warmer hat and a pair of gloves ;)