In article <slrnek27l8.91.dcferguson@dennispc.local>,
Dennis Ferguson <dcferguson@pacbell.net> wrote:
>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.

I'm not sure that's all there is. My wife has a V3c, and I tried a
Zip-Linq USB power supply rated 5V @ 1000 mA and got the same error
message.