Please forgive my rant. I just think this is unbelievable overdesign/oversight by Garmin.
I had a Garmin 370 that went kaput after 3 years. I purchased a 1350 LMT as a replacement that had great features. Alas, I promptly returned it, and will never buy a Garmin again. Here is why: because the new Nuvis are too stupid to know whether or not they are plugged into a computer.
My main problem: my car has a single cigarette lighter.
Because of this, I use a dual USB power cigarette lighter adapter (available at Wal-Mart for $7.99), and charge my devices via USB cords. This has worked swimmingly for years with a Nuvi 370, iPods, smart phones, cell phones, etc.
Again: no problems, for YEARS.
My 370 finally conks out after 3 years of service. No problem, time to upgrade anyway. I get a 1350. Great unit, except it refuses to work via USB power. It thinks it's plugged into a computer. No way to bypass storage mode to go the main menu. Absolutely, positively brain-dead design flaw.
The new Garmin Nuvis are the only devices in existence AFAIK that think they're plugged into computers while actually plugged into simple USB power. It's absolutely ridiculous, and tech support has basically told me I'm SOL.
You need to work with USB power, Garmin. In the meantime I'm buying a dashboard mount for my Android phone and using the Google Maps GPS.