I have two options for powering in the car. One is a simple USB adapter for the no-longer-a-lighter 12v outlet and the other is powering the wall adapter from an inverter that is plugged into the outlet. On long road trips with the kids, I power an inverter and have a 120v AC power bar so they can charge their various handhelds without fighting over a single USB connection and/or use devices that don't use USB. It is a decent enough inverter to provide enough juice for several DC adapters. But I have heard stories about using a DC adapter on an inverter causing problems. But my experience with the direct USB from 12v adapter is that it tends to charge things quickly but poorly (it charges my phone much faster than a wall adapter, but it will drain much faster also). Anyway, I would like to hear others' experiences and am especially interested if you have good working knowledge of power and charging and can explain why various ways are good/bad and whether or not it has a long term effect. I am specifically interested in charging/powering the a2109, but the other devices in play are iPods, 3DSes/DSes, Samsung phone and a generic MP3 player. They are not all being used and/or charging at the same time.