[JohnnieB]

The motor is mounted to differential, which is connected to axles, which are connected to the ground via the wheels and tires.
The cables are attached to things which are mounted to the body and frame, which are attached to the axles via springs.
The springs flex as the cart moves across bumps, so the cables flex.

The frame, body and battery tray also flex a bit, so even the cables between batteries are flexed a bit, especially when cart is driven across rough ground.