Abnormal battery depletion detection in an implantable device
Abnormal battery depletion can be detected in an implantable medical device. Battery capacity consumed can be measured using a coulometer and using a capacity-by-voltage device, and the measurements can be blended to determine battery status. A drop in battery voltage below a specified threshold can be detected to identify a high-current depletion fault, and an alarm can be provided to indicate the fault has been detected. The specified threshold can be determined as a function of battery capacity consumed. Other aspects and embodiments are provided herein.
1. A system, comprising:
a coulometer configured to measure battery capacity;
a capacity-by-voltage device configured to use a sensed battery voltage to measure battery capacity;
a controller, coupled to the coulometer and the capacity-by-voltage device, the controller configured to combine the measurements from the coulometer and the capacity-by-voltage device, using a weighted average of both of the measurements to determine battery capacity consumed, wherein a weight of each measurement in the weighted average is based on capacity remaining of the battery; and
wherein the controller is configured to detect a drop in the sensed battery voltage below one or more specified thresholds to identify a high-current depletion fault, the one or more specified thresholds determined as a function of battery capacity consumed as computed using the weighted average.
2. The system of claim 1 , wherein the controller is further configured to provide an alarm to indicate the fault has been detected.
3. The system of claim 1 , wherein the one or more specified thresholds include different thresholds corresponding to different portions of battery life.
4. The system of claim 3 , wherein the controller is configured to calculate the different thresholds using a substantially continuous function.
5. The system of claim 4 , wherein the battery capacity consumed is provided as an input to the substantially continuous function.
6. The system of claim 3 , wherein the one or more specified thresholds decrease in voltage over the battery life.
7. The system of claim 3 , wherein the different thresholds include at least seven separate threshold values.
8. A method for detecting abnormal depletion for a battery in an implantable medical device, the method comprising:
measuring battery capacity consumed by measuring an amount of charge provided by the battery;
measuring battery capacity consumed using a capacity-by-voltage measurement;
blending, using a weighted average, measurements from the measured amount of charge provided by the battery and the capacity-by-voltage measurement, wherein a weight of each measurement in the weighted average is based on capacity remaining of the battery;
detecting a drop in battery voltage below one or more programmable thresholds to identify a high-current depletion fault, the specified threshold determined as a function of battery capacity consumed as computed using the weighted average; and
providing an alarm to indicate the fault has been detected.
9. The method of claim 8 , wherein providing an alarm includes providing the alarm locally to a patient.
10. The method of claim 8 , wherein providing an alarm includes providing the alarm remotely over a communication network.
11. The method of claim 8 , wherein providing the alarm remotely over a communication network includes providing the alarm over an at least partially wireless network.
12. The method of claim 8 , wherein detecting a drop in voltage includes measuring battery voltage daily.
13. The method of claim 8 , wherein detecting a drop in voltage includes measuring battery voltage more than once daily.
14. The method of claim 13 , wherein providing an alarm includes providing an alarm when at least two battery voltage measurements are below the one or more programmable thresholds.
15. The method of claim 8 , wherein detecting a drop in voltage includes detecting and suppressing low voltage measurements that are due to voltage recovery from a non-fault high current draw condition.
16. The method of claim 8 , further comprising:
switching from using one threshold to another using one or more blended battery capacity consumed measurements.
17. The method of claim 8 , wherein detecting a drop in battery voltage below one or more programmable thresholds includes calculating at least one of the thresholds using a substantially continuous function.
18. The method of claim 17 , wherein calculating the thresholds includes setting at least one of the thresholds below a minimum voltage.
19. The method of claim 8 , wherein measuring battery capacity consumed using a coulometer includes measuring battery capacity substantially continuously.
20. The method of claim 8 , wherein measuring battery capacity consumed using a coulometer includes reporting battery capacity daily.
21. The method of claim 8 , wherein measuring battery capacity consumed includes measuring battery capacity in units of Ampere-hours (Ahr).