Dual Battery Pack System for Multi-Voltage Electric Vehicle Operation

Electric Vehicles (EV) have become a major focus in the automotive industry. This paper introduces a propulsion system design, which supports the Wide Torque Band (WTB) concept to boost the power density of PM (permanent magnet) motors in EV Trucks resulting in performance, efficiency, and cost benefits. The WTB drive requires an 800V battery for vehicle operation. The chosen solution combines two 400V battery packs to create a selectable 400V/800V DC bus. The electrical hardware and controls to manage the dual battery packs in either series (800V) or parallel (400V) mode are presented in this paper. A prototype battery management system (BMS) along with existing production Voltage, Current, Temperature Monitoring (VITM) hardware are applied to perform mode switching, safety, and cell balancing. The success of this dual pack hardware enables high voltage dynamometer testing of a new 800V DU (Drive Unit) and inverters for EVs. The flexibility of switching between two voltage levels (400/800V) from the battery packs enables testing of both current 400V and future 800V drive systems in the same test cell. The control concepts developed for managing the dual packs were applied to convert a truck to operate at 800V using the native 24-module battery with modifications. Vehicle tests validated the BMS with this new feature.