I'd research on how the car regains energy via braking. Friction from braking in turn turns the electric motor and enables it to charge the battery. Not sure if it's drawn from front or rear. No idea if changing out the brakes will affect the system either. Couldn't find an answer on wiki either.
CleanMPG, An authoritative source on fuel economy and hypermiling
I'd head over there ask pose the question in general forums. Pretty knowledgeable folk.