A conventional vehicle can be turned into a semi-hybrid vehicle using an ultra capacitor, a self-charging motor, and a number of different other components configured to maximize usage of vehicle waste kinetic energy. In one implementation, detected deceleration of the semi-hybrid vehicle causes the self-charging motor to pass electrical power to the ultra capacitor. In one implementation, the self-charging motor can also be used to further decelerate, or brake, the vehicle. After deceleration, such as upon accelerating the vehicle, the self-charging motor initially draws power from the ultra capacitor to add torque to the drive shaft, which can significantly reduce required fuel consumption. In another implementation, the semi-hybrid vehicle is configured to differentially engage refrigerant compressor power sources so that the refrigerant compressor can be synchronized with a mechanical power source before engaging. This can minimize or eliminate jerking of the vehicle during air conditioner compressor engagement.