Going 500 miles should not need an electric motor for assistance to compensate for a bike that is 10 lbs heavier before and travel kit or food or water is added to it. Better to have lower gears available so you can make your way however slowly up any grade of any length. What I appreciated as I got older and had more money was that I could leave the sleeping bag and camp stove and fuel bottle and ground cloth at home and eat in restaurants and stay at hotels along the route. The last thing I would want is to need to worry about how much juice was left in the battery or where I could plug in to recharge it each night. It misses the point much like using a motorcycle on the Pacific Crest Trail.