Smaller motor and bigger battery. If I pin the throttle on my "big" bike the battery takes a hit. If I pin the throttle on my son's 500W bike the battery hardly notices. If you can get by with a 250W or 350W motor, it will last longer per charge. My son's bike uses a "silverfish" style battery incorporated into the frame behind the seat post. Would be really easy to add another battery to the water bottle mount on the diagonal bar at the bottom of the triangle and even a third cargo rack battery. Of course the bike would weigh about the same as a boat anchor and its value would be significant based only on the cost of the batteries. Still that would be a 48V ~50-60AH battery all together. Considering his 500W bike can last 40 miles with a 12AH battery he could potentially go 200 miles per charge on a 60AH battery.