My model is the TomTom One. It took me a few tries to find the "Auto Off when power is removed" feature. The sequence is as follows: Touch the screen for Main Menu, Touch Change Preferences, Scroll right to Preferences 4 of 5, Select Brightness preferences. Touch Done. Touch Done again. The screen should now show a check box "Switch off when external power is lost" Checkmark the box if you want the automatic power down when the power from the car adapter is turned off. The TomTom will respond to power loss with a count down telling you that it will power off in X seconds unless you manually cancel the power down. Now my battery stays charged instead of running down every time I forget to power off. A nice feature!
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