Control strategy of an all-electric cruise ship based on cycle life mode of lithium battery pack

All-electric ships have become the main trend for the developments of touring ships; however, the frequent replacements of lithium battery packs still disturb the popularity of all-electric ships. This paper aimed at a class of pure electric sightseeing ships with the system of integrated electric propulsion. Based on the law of conservation of energy, a ship's mileage and remaining battery capacity model were established. The relationships between mileage, arrival time, and the cycle life of lithium battery packs were considered to establish the aging model of a lithium battery. In this study, we investigated an energy switching strategy of lithium battery packs based on logical threshold optimization algorithm to reduce their aging rates. The investigated strategy was verified by building Simulink simulation model and sample ship test. The simulation results showed that under the same environment, as compared with the general charge and discharge management system, the capacity attenuation of a lithium battery pack was greatly reduced, and the difference between the reduced attenuation amount and the original attenuation amount could reach 41%. The actual test showed that when the sample ship's voyage was at a uniform speed and straight line, the average aging serious factor of the lithium battery packs controlled by the proposed energy switching strategy was reduced by 0.1791 as compared with that of the general charge and discharge management system. This research validates that the proposed energy management strategy greatly can improve the cycle life of lithium battery packs.