AC adaptor

I can only say I tried a motorola phone charger with my nuvi750 and it will charge very slowly but will not get you to the navigation mode. I spent 20 bucks for the Garmin AC adapter and I now can charge and work with it at the same time without a PC.

as long as it is 5volts with at least 500ma, you should be ok. That is what a normal usb port gives ya.

The one I have the output is 5 v 850 mA.

I believe as long as you only want to charge the unit you are fine. If you want to be able to charge and get to the navigation mode with out a PC at the same time you will probably need the Garmin AC adapter. I have it and feel it is well worth the $20 or so.

I was wondering the same thing because I have a Moto cell phone charger with a mini-USB connection.
The cell phone chager says 500 Mili Amps. I went online, found the specs for the "official" nuvi AC chager and it said 1.0 Amps. I am guessing I could use the cell phone chager, it would just take longer. However, if I mess up the battery, I can't replace it so I will more than likely by the official one.

I think you are smart to get the Garmin charger. We spend a lot of money for the GPS and then try to cheap out on getting a good charger or work around trying to make another work. To me it doesn't make sense.