Do I need to buy a new car charger for this phone, or can I use the one from my Motorola since it has the micro usb plug? Are they all the same? One thing I noticed though, when I had my Razr connected to the car charger and was using navigation or even Pandora sometimes, it seemed like it never charged. It would just stay at whatever percentage it was at and never went up. Do different car chargers have different output?