Diagnostics and mitigation of battery cell failure with passive disconnect

1. A method of operating a battery pack of a vehicle, comprising:

obtaining a measured value of a battery parameter of the battery pack;

calculating an expected value of the battery parameter from a model of the battery pack;

calculating a first resistance ratio including the measured value, wherein the first resistance ratio is calculated based on a first drop voltage for a first cell group obtained during a rest period and a second drop voltage for a second cell group obtained during the rest period;

comparing the first resistance ratio to a second resistance ratio including the expected value to determine a blown fuse condition of the battery pack;

determining an available current from the battery pack based on the blown fuse condition; and

controlling an operational state of the vehicle based on the available current.

2. The method of claim 1 , wherein the expected value is indicative of a number of blown fuses in a cell group of the battery pack.

3. The method of claim 1 , further comprising calculating a capacity ratio and comparing the capacity ratio to an expected capacity ratio.

4. The method of claim 3 , further comprising calculating the capacity ratio using a first set of voltage measurements obtained from cell groups of the battery pack at a first time and a second set of voltage measurements obtained from the cell groups at a second time.

5. The method of claim 3 , further comprising outputting a capacity index based on the comparison of the capacity ratio to the expected capacity ratio.

6. The method of claim 5 , further comprising calculating a composite value from the resistance index and the capacity index and setting a current limit for the battery pack based on the composite value.

7. The method of claim 1 , further comprising outputting a resistance index value based on a result of comparing the measured value to the expected value.

8. A system for operating a battery pack of a vehicle, comprising:

one or more sensors for obtaining a measured value of a battery parameter of the battery pack; and

a processor configured to:

calculate an expected value of the battery parameter from a model of the battery pack;

calculate a first resistance ratio including the measured value, wherein the first resistance ratio is calculated based on a first drop voltage for a first cell group obtained during a rest period and a second drop voltage for a second cell group obtained during the rest period;

compare the first resistance ratio to a second resistance ratio including the expected value to determine a blown fuse condition of the battery pack;

determine an available current from the battery pack based on the blown fuse condition; and

control an operational state of the vehicle based on the available current.

9. The system of claim 8 , wherein the expected value is indicative of a number of blown fuses in a cell group of the battery pack.

10. The system of claim 8 , wherein the processor is further configured to calculate a capacity ratio and compare the capacity ratio to an expected capacity ratio.

11. The system of claim 10 , wherein the processor is further configured to calculate the capacity ratio using a first set of voltage measurements obtained from cell groups of the battery pack at a first time and a second set of voltage measurements obtained from the cell groups at a second time.

12. The system of claim 10 , wherein the processor is further configured to output a capacity index based on the comparison of the capacity ratio to the expected capacity ratio.

13. The system of claim 12 , wherein the processor is further configured to calculate a composite value from the resistance index and the capacity index and set a current limit for the battery pack based on the composite value.

14. The system of claim 8 , wherein the processor is further configured to output a resistance index value based on a result of comparing the measured value to the expected value.

15. A vehicle, comprising:

a battery pack;

one or more sensors for obtaining a measured value of a battery parameter of the battery pack; and

a processor configured to:

calculate an expected value of the battery parameter from a model of the battery pack;

calculate a first resistance ratio including the measured value, wherein the first resistance ratio is calculated based on a first drop voltage for a first cell group obtained during a rest period and a second drop voltage for a second cell group obtained during the rest period;

compare the first resistance ratio to a second resistance ration including the expected value to determine a blown fuse condition of the battery pack;

determine an available current from the battery pack based on the blown fuse condition; and

control an operational state of the vehicle based on the available current.

16. The vehicle of claim 15 , wherein the expected value is indicative of a number of blown fuses in a cell group of the battery pack.

17. The vehicle of claim 15 , wherein the processor is further configured to calculate a capacity ratio and compare the capacity ratio to an expected capacity ratio.

18. The vehicle of claim 17 , wherein the processor is further configured to calculate the capacity ratio using a first set of voltage measurements obtained from cell groups of the battery pack at a first time and a second set of voltage measurements obtained from the cell groups at a second time.

19. The vehicle of claim 17 , wherein the processor is further configured to output a capacity index based on the comparison of the capacity ratio to the expected capacity ratio.

20. The vehicle of claim 15 , wherein the processor is further configured to output a resistance index value based on a result of comparing the measured value to the expected value.