For designing a high performance electric vehicle capable to run a quarter of a mile in 10 seconds, it is necessary to use ultracapacitors because they have high power density and their shelf life is longer than other conventional storage elements. These elements will feed four PM motor with a higher voltage requirement, so it is important to increase the power density of the DC-DC converter which interfaces the ultracapacitors with the motor drivers. In these conditions, a novel high power DC-DC converter is studied looking for a high efficiency with a small size. This work shows the design of a high power density interleaved DC-DC converter using closed-coupled inductors and the development of a prototype.