I've use my N800 (not an N810 of course) on 10+ hour trips, and the battery was completely full at the end, every time. I use a cable I got off ebay for almost nothing, plugged into a USB charger in my cig lighter outlet, and it charges far quicker than my bluetooth GPS and Maemo Mapper run it down. You should be able to run almost anything you want simultaneously for all day, as long as you have a proper power source connected.