Patent ID: 8692507

Claim:
A multiple stage traction battery system, comprising: a primary traction battery module coupled to an electric motor; a secondary traction battery module coupled to said electric motor and said primary traction battery module; a DC/DC converter and controller, coupled to said primary traction battery module and said secondary traction battery module, that adjusts an output power limit and that moves energy from said secondary traction battery module to said primary traction battery module, and maintains preset state of charge ranges in said primary traction battery module and said secondary traction battery module; wherein said DC/DC converter and controller maintains a narrower state of charge range in said primary traction battery module than said secondary traction battery module, thereby allowing for higher charge/discharge rate and lower utilization rate in said primary traction battery than said secondary traction battery; and a charger, that charges said secondary traction battery module from an external power source based on a state of charge of said secondary traction battery module.