Got a used 2014 i3 rex this week. Loving it so far, but I've noticed a peculiar thing about the battery.
When I first charged it, I took a screenshot in the app for each hour of charging, and noticed a consistent 5% per hour, except an immediate jump from about 68-75 percent, shaving an hour off of the expected charge time. I then noticed an almost immediate drop when driving. Went from 75-65 in two kilometers driving at 65km/h.
Charging again now, and same immediate jump from 68-75%.