Check my ride from last week, i went on a type of MTB marathon,
http://www.sportypal.com/Workouts/Details/6556
i had excellent time, we drove around 90 km. Took a nokia n78 with me, turned on the sportypal and leave it working in the background in my backpack. After 8 hours when came to the finish the battery was more than 50 % full,