After two separate 6+ hour trips (one Sunday, one Monday), it charges with the charger I was using, but very slowly. I estimate that I was probably around 50% charge when I began my trip on Sunday, and after 6+ hours of navigating, it was only around 80% charged.
Same thing with Monday's, although the percentages were different.
I will note, I'm using the car charger that I got with my Droid 2 Global with the window mount for the DINC2.
EDIT: Also, when making this similar trip in the past with the Droid 2 Global, I never had any issues with it not charging up to 100% while navigating...and this was probably from a low of 30-40%.