Patent ID: 6166524
Filing Date: 2000-12-26
Classification: H01M,Y02E

Abstract:
In combination with an implantable medical device requiring a substantially constant discharge rate during a medical device monitoring function and at least one pulse discharge for a medical device operating function, the combination comprising:a) an electrochemical cell comprising an alkali metal anode and a solid cathode activated with a nonaqueous electrolyte, wherein the cell has a determinable stoichiometric capacity;b) electronic circuitry powered by the electrochemical cell for discharging the cell under a first load condition and at a second, lighter load or at an open circuit voltage condition, wherein the first load occurs during a medical device operating mode for charging a capacitor or delivering therapy and the second load occurs during a medical device monitoring mode;c) wherein the electronic circuitry provides for determining the remaining discharge capacity in the cell by having the first load condition removed from the cell at a first time so that the cell's discharge voltage relaxes from a first voltage at the first load to a second voltage at a second, lighter load or at an open circuit voltage condition and measuring the voltage change from the first voltage to the second voltage, wherein the time interval for the cell to relax from the first voltage at the first time to the second voltage at the second time is measurable and wherein the voltage change is divisible by the time interval to determine a .DELTA.V/.DELTA.T ratio and wherein the calculation of the .DELTA.V/.DELTA.T ratio is repeated for at least two additional times to obtain at least three .DELTA.V/.DELTA.T ratios; andd) wherein the .DELTA.V/.DELTA.T ratios are comparable to perform an analysis on the slope of the resulting curve to thereby determine the discharge capacity remaining in the cell.