You must not be pushing the gas down at all getting that sort of range on a e35 model, did you do a 280 miles trip on 1 single charge from 100%?
I’ve been averaging 2.8kw (201 miles at 100%) unfortunately enjoying the rapid power of the car, I’m trying to get to 3-3.5kw maybe cruising on a motorway trip will help, have yet to go on it.