Lightweight polymer–carbon composites with high specific electrical conductivity at a carbon content below 40vol.% were developed. The electrical and mechanical properties and the hydrogen permeability of carbon fiber and particle reinforced liquid crystalline polymers were examined. Vectra® A 950, SIGRAFIL® carbon fibers and Vulcan® XC 72 R carbon black were employed. The composites are found to have sufficient mechanical properties and a hydrogen permeability low enough to be utilised as bipolar plate material in fuel cell applications. The density of the new composite is 20% lower than the density of commercial bipolar plates made from carbon reinforced polymeric composite materials, due to the lower carbon content. The current density at 0.5V in an operating fuel cell is only 20% lower compared to commercial materials with more than 80vol.% carbon content and meets the requirements for bipolar plate application.