@mikpetter @DoomsdaysCW @Brad_Rosenheim Supercapacitors have very high discharge/recharge rates and can be cycled many times, but don't hold a lot of juice. Some sort of hybrid system seems like a good idea to me. Dump regenerative braking energy into the capacitor instead of the battery (reducing wear and tear on the battery), but have the battery there to ensure a constant supply of electric assist.