Hybrid electric vehicle and propulsion system

A hybrid electric vehicle drive system comprising a combustion engine (79), an electric motor (76) and at least one nickel-metal hybride battery module (75) forming a power source for providing electric power to the electric motor (76), the at least one nickel-metal hybride battery module having a peak power density in relation to energy density as defined by : P > 1,420 -16E where P is the peak power density as measured in Watts/kilogram and E is the energy density as measured in Watt-hours/kilogram.