I have a Carrera Crossfuse with a 400 at Bosch battery. It's about 2.5 years old, I sometimes go out with friends on longer rides and, as my battery starts to degrade, I am thinking of replacing. Does anyone know If it is viable to move up to a 500wh with out any modification to the motor. Or would you recommend buying another 400 wh and just carry my old as back up on really long rides?