I just got back from a road trip with mine. Here is what I found. I have this USB adapter that I use in my truck to charge my devices.
Car charger
When I used my new POGO cable while using my N10 for navigation, I was losing charge faster than I thought I should. When I plugged in my old USB cable to the micro USB charging port on the N10, it was able to maintain the same percent. I then tried plugging in my POGO charger at the same time as the micro USB charger and it seemed to charge even faster. I am going to have to do some research on this to see if it really is charging faster. I would also like to know if this might be bad for it. It may be that one of the charging ports is disabled automatically when the other one is used. I have no idea, but it would be good to know this stuff.
As far as using your N10 for navigation, I found that if you keep the screen on and the nav up on the screen all the time, it drains REALLY fast! If you start the nav, hit the home key, let it run in the background and turn off the screen, it will still guide you via voice prompts and it will actually charge the device while it is plugged in. When I got to areas that I really wanted to see the map while navigating somewhere, I just asked my wife to bring it up on the screen.