Elcykel – Regenerering med BLDC-motor och DC/DC-omriktare

Abstract
The electric bicycles of today are usually not constructed for regeneration, instead the
batteries are only charged from the electric grid. Recharging the battery by reuse of kinetic
energy may increase the range or reduce the size of a suitable battery. Hence, in this project a
DC/DC-converter, that together with already existing parts of the bicycle, is constructed to
provide the reuse of the kinetic energy. The regenerating circuit is of buck-boost circuit type,
which is based on the integrated control circuit LM5118 from National Semiconductor. The
theories behind a BLDC-motor and a buck-boost circuit are briefly described. The analysis of
the circuit, which does not fully work, shows that efficiency above 90% can be reached with
the kind of DC/DC-converter that is constructed. In the end of the report, some suggestions
about further development of the circuit and some interesting studies that can be made, are
given.