Technicians now close up the fully assembled battery with protective covers and run it through a function test. The test simulates the discharge of the battery that happens when you ride the bike. Then the recharge that occurs when you plug in. All the cell voltages must balance in the process. The motorcycle frame is made of high strength, lightweight, aircraft grade aluminum. At the tail end, they install the controller; the link between the battery and the throttle, which controls the electricity flow to the motor. They mount a suspension system … an aluminum swing arm that attached to the rear wheel on one end, and to the frame on the other, via a spring shaped shock absorber, which expands and contracts to dampen bounce as the wheel moves up and down over bumps in the road.