I used to do that with my Garmins, but I now simply use the iPhone for Maps, "GPS", routes, MPH, weather, etc., etc.
Unfortunately, I need 6v-12v converter, or a 12v "power-pack" (like my DeWalt 2800 Peak Amp Jump Starter 1000-Watt Power Inverter with Digital Compressor, 120v power outlets, USBs, and, I think it can also whistle Dixie in 3-part harmony - part of my long-distance travel assurance/insurance).
Although, one of my 7"-screen Garmins also has back-up camera (that stays in/with my COE flatbed).
Not so fast Tim. iphone chargers and I trust all the others work just fine on 6 volts. The output of the automotive phone chargers is around 5 volts. 6v input has proven very OK in my experience. I tapped into the hot side of the ignition switch, added a fuse and installed an inexpensive auto charger (from Oriellys) in the capped off cigar lighter port in the dash. The black plastic snap in cover when the charger is removed looks pretty dang stock. I wired it so it was hot all the time allowing the phone to charge when not driving.
My smarter than me electrical engineer little brother is responsible for this idea.
