Well I'm not sure. You are probably thinking of just smoothly riding down a hill, but every time I push on flat or up, the plunger would fly forward, and if I footbraked or slided to stop it would move the other direction. And if one was perpendicular to the board when I turned, G-Force would push it to the outside of the turn until it dropped down enough which would cause gravity to pull it back, because the tube would be at an angle.
Really it comes down to how complex is a charging circuit for varied amperage and voltage like that?