One of the fun things about being on a rover team is it gives me an opportunity to play with hardware far out of what I’d normally encounter. Much of that falls in the category of power, as we design for about a kW of draw running on 12V (for now).
A feature of our emergency stop system is a pair of 260A automotive relays, which I recently fried. While disappointed to have ruined a rather expensive relay, I was excited to take it apart. Pictures below, and after that an explanation of what went wrong.
So, what went wrong? Well, see those reverse protection diodes? Wired power up backwards. Rover batteries were happy to pump some 200A through them. The fix? A couple new diodes.