I got that warning 2 or 3 times, in sport mode, on the first 2 or 3 flights, but over the last 6 weeks I haven't had that 'battery over-current' warning. And I spent a couple of weeks at over 6000' elevation flying in sport mode in 85-90 degree temperaturesThe Mini 3 batteries will also last up to 3 times longer than the Nano's. You just can't push them as hard without getting that 'overdraw' red-flag warning on the top of the telemetry screen.
so I'm wondering if that over-current warning is just a symptom of a brand new battery on it's first or second flight