NiMH-Batteries in Modular and Bipolar Design for Application in Advanced Board Net Structures and HEV

摘要

The number of electrical components of modern road vehicles and their power demand leads to new requirements for the electrochemical storage device in the new board-net structures. Especially fast cycling ability including comparatively high electric currents are expected. Taking into account the life time requirements of the car components alkaline batteries are taken into consideration. From alkaline systems the nickel metal hydride battery is displaying the most appropriate properties for such an application. During the last years nickel metal hydride batteries for high power demands are under investigation. The cells make use of the advantages of the fiber structure electrode technology and a AB5 hydrogen storage alloy. This technology has been applied before for various Ni/Cd industrial and vehicle applications. The Ni/MH batteries are build in single cell and modular design. 12 V and 36 V units have been operated under board-net conditions. The experiments demonstrate the high charging efficiency of the nickel metal hydride system. Pulse discharge experiments have been carried out at various temperatures. Pulse discharge with currents up to 10 C have been carried out at low temperatures (-30°C). In bench tests the high stability of operation have been proved. Due to the special properties of the Ni/MH-system the batteries require some modification of the charger management. Another design based on a bipolar cell concept is offering even higher power abilities. Bipolar Stacks of 12, 36 and 110 V have been built and operated in bench tests. The expected advantage of a bipolar stack for an application in HEV consists in minimising the size of the battery for a given power demand and the expanded cycle-life of alkaline batteries. In addition the application of small high power batteries will contribute to reduce the costs of the battery in HEV.