With an e-bike and two batteries, I rode 33 km (20.5 miles one way) to Lake Moulin, climbing 4546 feet in elevation. Just in case, I was given two batteries, which I needed. The second died 100 meters from lake. Didn’t need them, just coasted the whole way down. With lunch and breaks, 9 hours (9 to 18). Be sure to stop at Lake Lexert too, beautiful. Stupendous routes to two gorgeous lakes, all while following the Buthier river or torrente as they say here.