I recently bought two Revolutionworks 24V pedal assist units. Went to Burning Man and bolted them on to our junky old playa bikes. Worked very well for a couple of aging hippies. Problem is that they claimed 12 mile range with the 100wh model, but we got barely half that. They will sell me extra batteries, but only the small one will fit this unit. The charger is a fairly standard 29v brick and the charging port looks pretty standard. I am thinking of trying to get a larger battery and piggy backing it into the charger port. Revo says that won't work.