Lithium Iron Phosphate (LiFePO4) Battery Power System for Deepwater Emergency Operation

Abstract Unmanned underwater vehicles (UUV) are widely used for survey and mining of natural resources in the region of underwater and seabed in the last two decades. In underwater, vision and depth perception will be poor, thus navigating and maneuvering a remotely operated vehicles (ROVs) will not be an easy task. The umbilical cable might get entangled. In the event that the ROV loses power from its umbilical cord or an autonomous underwater vehicle (AUV) power failure, an emergency power system will be needed to power the critical equipment on the ROV or AUV to facilitate its recovery and to limit the loss of data. In this paper, a large format 2 KWh lithium iron phosphate (LiFePO 4 ) battery stack power system is proposed for the emergency power system of the UUV. The LiFePO 4 stacks are chosen due to their high energy density, modularity and ready availability. The proposed LiFePO 4 battery system includes the design and development of a smart battery management system (BMS) with high efficiency active cell balancing technology and intelligent self-learning battery state of charge (SOC) estimation for the LiFePO 4 battery. The proposed BMS will lead to better utilization of battery’s potential capacity and maximize the cycle life of the battery. The battery system has a pressure-resistance enclosure to eliminate extra battery pressure chamber and associated risks, therefore increase the reliability of the power system amidst high pressures down to 3km of deep-water.