Patent ID: 8859123

Claim:
A lithium-ion electrochemical battery system, comprising: a first electrode; a second electrode spaced apart from the first electrode; a separator positioned between the first electrode and the second electrode; an active material within the second electrode, wherein a volume of the active material increases as a state of charge of the battery system decreases, and the battery system is configured such that an increase in the volume of the active material causes an increase in a pressure within the second electrode; a pressure sensor in fluid connection with the second electrode; a memory in which command instructions are stored; and a processor which is operated to execute the command instructions programmed into the memory to obtain a pressure signal from the pressure sensor indicative of the pressure within the second electrode which is substantially isolated from a pressure within the first electrode, and to identify the state of charge of the battery system by correlating the pressure signal with stored date indicative of a relationship between a range of pressures within the second electrode and a range of states of charge of the battery system.