Haven't managed to log a pre-heat yet (mainly because I haven't wanted to sit in a car while it's preconditioning), but I have some data on battery temperature during driving.
I did a run from Coventry to West London a week or so back, and logged a few things. External temp was about 7C, and I'd done a small run in the morning which had lifted things a couple of degrees from that.
Pretty much the only thing that raised the battery temperature at all, was charging. During general driving (most of this was 65-70 mph motorway). Don't read anything into the very linear rise on the second charging stop, I didn't log that one because I went and ate dinner. It's just drawing a line between before and after values.
One thing that's quite interesting is if I zoom in on the first charging stop, and add the charging current.
Reminder: 50kW is 125A at 400V. The red envolope is the min/max temps reported by cells, with the average in bright red.
At the start is ramped straight up to 125A (50kW), but then settled back down to about 70A (28kW). I wasn't best pleased with this at the time, but looking at the graph it seems like every time the battery pack reported a 1 degree rise, the power went up a little. By the end it was sending 100A (40kW). Each degree seems to allow another 5A (2kW) of charging speed. At that rate I'd expect to get full speed around 22 degrees C.
Other things I've found:
- The relationship between the SoC displayed on the dash and the true internal SoC is linear. It's just capped at top and bottom, but there's no funny curve to account for. So if you want to do calcs where 1%=xxxWh to calculate range and things, there's no gotchas.
- SoC seems to be strongly related to pack voltage, but it's more complex than that.
- I've seen the pack deliver a peak a little over 400A under hard acceleration. That was about 130kW given the pack voltage at the time (325V). Given it's a 125kW motor, that makes sense.
- Under regen I quite commonly see 125-140A flowing back into the battery. That seems to be 50kW, adjusted for the pack voltage. So you can accelerate at 2.5x the power that you can regen brake.
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