@Turtlew
Depending on which device you have it may be possible to use a standard miniUSB data cable from one of your vehicle's USB sockets with the following kludge:
  • Hold the battery symbol of the main "Where To?/View Map" page for about 5 or 6 seconds until it shows a hidden page "SW Ver .....".
  • Plug in the data cable to the device
  • Exit the hidden menu
  • Let the device reboot and it should stay in navigation mode

Note that if the 5v source is delivering insufficient current to both power and charge the device the above trick won't work. Some devices need 2 Amps others only 1 Amp. Also it doesn't work successfully with all Garmin devices.

You can modify a standard 5V usb cable to act like Garmin's proprietary charger at the mini plug end. It's the pinout setup which tells the device to go to Mass Storage Mode or stay in navigation mode. More info here:
Code:
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Another solution might be to add an after-market ciggy socket directly to the vehicle wiring, with suitable fuse protection of course. They're inexpensive to buy in electronics or auto accessory stores and as cheap as a buck delivered from China, e.g.:
Code:
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