I think there is some time you have to allow when you shut off the car then turn it back on again. If you cycled too quickly, the P1900 might still be in lockout and power off mode.

As for blowing 3 fuses, well, that obviously wasn't right! It sounds like you've damaged the Mini. When you say you brought it back inside, did you hook it up to the wall outlet using the Mac power brick, or did you use the P1900?