To the OP. You might think about making a dock for the mini. Mine is in my project page here. 1995 240SX Mac Mini Lilliput 7"
I take mine in the house pretty often too and the little connector for the macpac power button wasn't gonna cut it. The little solenoid i used to press the power button has been working perfectly for about a year now. I also don't have the p1900 hooked up to the car ignition switch just cause i hate the carputer turning off when i stop at the gas station or the store. The Optima yellow top battery is awesome by the way.