I have several USB-MicroUSB cables (some OEM Motorola, some other brands), several 12 volt-USB converters, several cars, and several devices that accept MicroUSB connection for power. With everything other than my Droid (including a Blackberry and a GPS unit) every combination of cable and 12volt converter works. With the Droid, all of the combinations will turn on the screen (indicating the Droid knows a cable has been connected), but only a few combinations will actually charge the Droid. The only possible explanation I have come up with for this is that the Droid has some sort of minimum current requirement, and that some converter/car/cable combinations are unable to meet this requirement. So, what is the minimum voltage and current that will allow the Droid to charge? And, does anyone have any other ideas about this?