NOVELTY - The system (100) has a battery cell including a shell encasing a positive electrode, a negative electrode and a separator positioned between the positive electrode and the negative electrode. A wireless temperature sensor assembly is encased within the shell. The wireless temperature sensor assembly is provided with a negative electrode wireless temperature sensor and a positive electrode wireless temperature sensor, where the negative wireless temperature sensor is located within the negative electrode and the positive wireless temperature sensor is located within the positive electrode.    USE - Lithium-ion battery system for a vehicle.    ADVANTAGE - The sensor assembly includes a thin flexible electronic circuit that is self-contained and chemically isolated from battery materials by a thin polymer film encapsulation, that includes an antenna loop to receive and send radio signals and that powered by externally generated radio waves similar to RFID devices such that an outgoing signal is modulated by a solid-state thermal sensing element i.e. thermocouple, and contains information about the particular cell and internal temperature, so that no external leads are required for internal temperature measurement of the electrochemical cell. The flexible electronic circuit is self-contained without need to weld contacts to tabs of metallic current collectors, so that integration can be simply achieved by placing the sensor between electrode layers inside the battery cell without significant design changes to the cell.    DETAILED DESCRIPTION - The wireless temperature sensor assembly includes an RFID transponder. An INDEPENDENT CLAIM is also included for a method for controlling a battery system.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of a lithium-ion battery system including electrochemical cell packs that are independently controlled.    Lithium-ion battery system (100)    Load or voltage source (104)    Processor (110)    Memory (112)    RFID transponder (154)