Mechanical batteries have been drawing interest due to their longer life time and bigger depth-of-discharge ratings. Also, they do not have the adverse effects on the environment as the electro-chemical batteries. In mechanical batteries, an electric machinery is run in motor mode at a constant speed, storing kinetic energy in its inertia. When there is a need of energy, the machine is operated in the generator mode and the kinetic energy is returned to the system as electrical power again. These systems are also being considered for space systems for the future. In these systems, regenerated voltage needs to be regulated at the bus level of the space vehicle. Using the inverter that drives the motor as a controlled rectifier in the generator region is proposed in this paper. The system is explained and experimental results are given for a small system to demonstrate the concept.