On 2006-10-24, Z Man <z1z@hotmail.com> wrote:
> I bought a car cord/charger at a computer show. It fits perfectly, but I get
> a message on the phone that reads "unauthorized charger". I have done some
> research and found that this occurs frequently with after-market chargers,
> and sometimes even with OEM charges. Usually, folks raise this question when
> they plug their phone into the USB port on their computer. I am only
> concerned with car use and charging. Regardless of the message, will the
> phone still drawer power from the car? Will it still charge?

Here's the problem. The USB specification limits the minimum power
available from the interface voltage pins to 500 mA at 5 volts, or 2.5W.
The GSM version of the RAZR, which first adopted the USB charger cable,
can apparently live with that, but the CDMA phone is more power hungry and
needs more than 2.5W to charge. The chargers supplied by Motorola will
deliver significantly more than 500 mA, and as a practical matter a lot
of other USB chargers and interfaces will too, but with the latter you
can't count on them to support more than the standard requires. While
the phone still uses a standard USB jack for the charger, the power
requirement is non-standard.

The "unauthorized charger" message is hence telling you that the power
output of your charger is significantly lower than a Motorola charger
would provide. It may or may not still charge the phone, you'll have
to try it to see. If it does charge the phone it will take longer to
do so than a higher power charger would. If you were sold this charger
explicitly for use with that phone you got shafted, but otherwise it
is just an unfortunate incompatibility caused by the non-standard
power draw those phones need from their USB interface.

Dennis Ferguson