A novel pressure compensated structure of lithium-ion battery pack for deep-sea autonomous underwater vehicle

The battery pack of deep-sea autonomous underwater vehicle (AUV) is placed in a heavy shell to protect the batteries from external pressure and moisture in a conventional manner. In recent years, the pressure compensated structure with thin film based on oil immersion has been gradually applied to the deep-sea AUV battery pack to achieve lightweight design. In this paper, the ratio of the structural parts of the pressure tolerated and pressure -compensated structures of the cabin to the total weight of the battery pack is systematically analyzed respectively in the depth range of 300- 6000 m, and a new pressure compensated structure with piston based on oil immersion is proposed. The mechanical properties and thermal characteristics of this structure are simulated and analyzed. Finally, the functionality of the compensated structure is verified by the established pressure test platform. The results show that the weight of conventional pressure tolerated structure increases nonlinearly with the increase of hydrostatic pressure to resist external hydrostatic pressure. The proposed pressure compensated structure with piston not only saves at least 18.3 % of the structural component weight at a hydrostatic pressure of 60 MPa, but also reduces the surface temperature of the battery pack due to the presence of dimethyl silicone oil as a pressure transfer medium.