you've also gotta consider that the load on the alternator is a lot less than in a factory install - you're not running a lot of the electrical ancillaries like twin radiator fans, A/C fan etc.
the alternator fan should only be needed when the car is idling in traffic with the A/C going flat out - which is when the electrical system would be trying to draw the most current from it
If you're concerned, wait for a hot day and turn on your high beams, the A/C, radio, open the doors (interior lights) and turn on anything else that uses electricity in your daily driver and use a temperature gun to check the temperature of your alternator, then do the same with the mini with the alternator running backwards - I bet it doesn't come close
this may be a good read -
https://www.electronics-cooling.com/200 ... ectronics/
_________________
did I tell you that I won a
trophy?