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US 2003/0149455 A1Published application
Method and apparatus for determining depleted capacity of a battery
AssigneeSt. Jude Medical, Inc.
InventorsMartin Obel, Jan Lindberg
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AssigneeSt. Jude Medical, Inc.
InventorsMartin Obel, Jan Lindberg
Estimating the term…
A method of detecting the status of the battery of an implantable heart stimulator comprises the steps of measuring the impedance of the battery, detecting an increased value of the measured impedance, determining an impedance based value of the remaining capacity of the battery from the detected impedance increase, combined with the steps of measuring the total charge depleted from the battery, and determining a charge depletion based value of the remaining capacity of the battery. A battery status detecting circuit for an implantable heart stimulator includes a first measurement means (12) for measuring the impedance of the battery (6), a detection means (14) for detecting an increased value of the measured impedance, a first determination means (16) for determining an impedance based value of the remaining capacity of the battery from the detected impedance increase. A second measurement means (22) is provided for measuring the total charge depleted from the battery, and a second determination means (24) is provided for determimng a charge depletion based value of the remainig battery capacity.
A method for determining depleted capacity of a battery of CFx type used in an implantable medical device, characterized in that average values of battery voltage and current drawn from the battery (2) are measured during a measurement time, the length of which exceeds a battery voltage recovery time after a load change, and in that predetermined relations between, on one hand, combinations of average values of voltage and current and, on the other, depleted battery capacity are used for determining depleted capacity of the battery from said measured average voltage and current.
The method according to any one of the preceding claims, characterized in that said battery recovery time equals a time within the range 3-50 h.
The method according to any one of the preceding claims, characterized in that said measurement time exceeds 24 h.
The method according to any one of the preceding claims, characterized in that said average values of voltage and current are entered into a predetermined look-up table providing depleted battery capacity for different average voltage and current combinations.
The method according to any one of the preceding claims, characterized in that depleted battery capacity is also determined by time integrating the total current drawn from the battery.
An apparatus for determining depleted capacity of a battery of CFx type used in an implantable medical device, characterized in that averaging means (10,12) are provided to determine average values of battery voltage and current drawn from the battery during a measurement time, the length of which exceeds a battery voltage recovery time after a load change, and in that a determining means is provided for determining actual depleted battery capacity from predetermined relations between, on one hand, combinations of average values of voltage and current and, on the other, depleted battery capacity.
Dependencies are inferred from the claim text.