This paper presents a medium scale prototype of a system to store the excess energy present in a DC electrical system, based on Ultra-capacitors and driven by a DC-to-DC converter. The prototype is first intended for research and pedagogic proposes, and second as a voltage stabilization system in Medellin's Metropolitan Train System where it is being implemented. This allows students and researchers to perform experiments regarding regenerative braking, power line compensation and high-current DC-DC electronics. It is based in previous work with simulations and a small prototype developed for the student in the Electrical and Electronics Laboratory in the Universidad Pontificia Bolivariana.