I had an Atrix 4G, but returned it a couple weeks ago. While I had it I bought a car charger on eBay for cheap. It worked fine with the Atrix. However, now I have moved to T-Mobile and have a used MyTouch 3G. Since I bought it used, not from T-Mobile, I have no insurance or warranty. Therefore, I am a bit cautious about plugging it into the car charger. My thinking is that the car charger must be providing the same current as a standard USB port on a computer. I can charge the MyTouch 3G off the USB port on my computer just fine, so I assume the voltage would be the same. But I thought I'd ask here before frying my new (used) phone.