[kithmo]

I don't have a Soul EV yet but would guess that if the charger is off then it would use the main battery.
Can you check the charger status, separate from the car, to see if it's operating during the preheat process?

 

[kithmo]

Are you looking at getting the Soul EV?

Maybe about the middle of next next year. It looks a better prospect than the new MG ZS for my needs and not much of a price difference now the grant threshold has been lowered.
Being the third generation, I would guess most of the foibles are ironed out now and the 280 mile range seems quite realistic on the Soul according to reviewers.
ISTR reading that Kia quote the actual useable battery size, not the overall size like many manufacturers do and so it also looks quite efficient on mpkwh.