Chargeable battery abnormality detection apparatus and chargeable battery abnormality detection method

1. A chargeable battery abnormality detection apparatus configured to detect an abnormality of a chargeable battery, the chargeable battery abnormality detection apparatus comprising:

a processor; and

a memory storing instructions executable by the processor,

wherein the processor performs the following when executing instructions:

calculating a value of an internal resistance of the chargeable battery;

determining whether the chargeable battery is being charged or being discharged;

determining that an abnormality has occurred in the chargeable battery if either one of the following occurs:

the calculated value of the internal resistance decreases while the chargeable battery is being discharged; and

the calculated value of the internal resistance increases while the chargeable battery is being charged; and

outputting a determination result of the abnormality,

wherein after determining that the abnormality has occurred, the processor determines that the abnormality has been resolved if a value obtained by dividing a value of the internal resistance at a certain time point at or after a point in time when the processor determined that the abnormality has occurred in the chargeable battery by a maximum value of the internal resistance at or after the point in time when the processor determined that the abnormality has occurred falls below a first predetermined threshold value.

2. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor obtains a voltage and a current at a load when the current flows in the load, and the processor calculates the internal resistance on the basis of the obtained voltage and the obtained current.

3. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor sets an equivalent circuit of the chargeable battery and causes a voltage and a current of the chargeable battery to be measured, and the processor calculates the equivalent circuit on the basis of the measured voltage and the measured current through a learning process.

4. The chargeable battery abnormality detection apparatus according to claim 1 ,

wherein the processor also determines that the abnormality has occurred in the chargeable battery when the calculated value of the internal resistance increases greater than a value in a normal state of the chargeable battery while the chargeable battery is being discharged,

wherein the processor determines that the calculated value of the internal resistance increases greater than the value in the normal state of the chargeable battery if a ratio or a difference between the value of the internal resistance at a present time and the internal resistance at a past predetermined time when the chargeable battery was in the normal state exceeds a second predetermined threshold value, and

wherein the processor refers to a prepared table that stores a discharge current and said second predetermined threshold value in association with each other, and acquires the second predetermined threshold value according to the discharge current from the table.

5. The chargeable battery abnormality detection apparatus according to claim 1 ,

wherein the processor also determines that the abnormality has occurred in the chargeable battery when the calculated value of the internal resistance increases greater than a value in a normal state of the chargeable battery while the chargeable battery is being discharged, and

wherein the processor determines that the calculated value of the internal resistance increases greater than the value in the normal state of the chargeable battery if a value ΔR/ΔSOC obtained by dividing ΔR by ΔSOC is less than a prescribed negative threshold value, where ΔR represents an amount of increase in the calculated internal resistance R per a predetermined time period, and ΔSOC is a negative value representing an amount of change in a state of charge SOC per a predetermined time period.

6. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor determines that the calculated value of the internal resistance increases while the chargeable battery is being charged when a difference between the calculated value of the internal resistance at a present time and the internal resistance at a past predetermined time when the chargeable battery was in the normal state exceeds a second predetermined threshold value.

7. The chargeable battery abnormality detection apparatus according to claim 1 ,

wherein the processor also determines that the abnormality has occurred in the chargeable battery when the calculated value of the internal resistance increases greater than a value in a normal state of the chargeable battery while the chargeable battery is being discharged, and

wherein the processor determines that the calculated value of the internal resistance increases greater than the value in the normal state of the chargeable battery if a difference between the value of the internal resistance at a present time and the internal resistance at a past predetermined time when the chargeable battery was in the normal state exceeds a second predetermined threshold value.

8. The chargeable battery abnormality detection apparatus according to claim 1 , wherein when the processor detects a short circuit as the abnormality, the processor causes the detection to an external processor, and stop charging the chargeable battery.

9. The chargeable battery abnormality detection apparatus according to claim 1 , wherein when the processor detects a polarity inversion as the abnormality, the processor controls an alternator to charge the chargeable battery.

10. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor estimates a temperature of an electrolytic solution in the chargeable battery and normalizes the calculated value of the internal resistance to a value in a standard state.

11. The chargeable battery abnormality detection apparatus according to claim 1 , wherein in determining whether the abnormality has occurred in the chargeable battery, the processor also refers to an open circuit voltage of the chargeable battery.

12. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor determines that the chargeable battery has been short-circuited when the calculated value of the internal resistance increases while the chargeable battery is being charged.

13. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor also determines that the abnormality has occurred in the chargeable battery when the calculated value of the internal resistance increases greater than a value in a normal state of the chargeable battery while the chargeable battery is being discharged.

14. The chargeable battery abnormality detection apparatus according to claim 1 , wherein the processor calculates the value of the internal resistance by dividing a fluctuating value of a voltage in a predetermined time period by a fluctuating value of a current in the predetermined time period.

15. The chargeable battery abnormality detection apparatus according to claim 1 , further comprising a voltage detector that detects a voltage of the chargeable battery,

wherein the processor further determines that the abnormality has occurred in the chargeable battery when the voltage detector detects a voltage drop corresponding to a voltage of one cell among a plurality of cells constituting the chargeable battery.

16. The chargeable battery abnormality detection apparatus according to claim 1 , wherein when the processor detects a polarity inversion as the abnormality, after determining that the polarity inversion has occurred, the processor determines that the abnormality of the polarity inversion has been resolved if the calculated value of the internal resistance increases again after the processor has determined that the polarity inversion has occurred and then decreases.

17. The chargeable battery abnormality detection apparatus according to claim 1 , wherein after determining that the abnormality has occurred, the processor determines that the abnormality has been resolved if a voltage of the chargeable battery increases to reach or exceed a second predetermined threshold value after the processor has determined that the abnormality has occurred in the chargeable battery.

18. A chargeable battery abnormality detection method of detecting an abnormality of a chargeable battery, the chargeable battery abnormality detection method comprising:

calculating a value of an internal resistance of the chargeable battery;

determining whether the chargeable battery is being charged or being discharged;

determining that an abnormality has occurred in the chargeable battery if either one of the following occurs:

the calculated value of the internal resistance decreases while the chargeable battery is being discharged; and

the calculated value of the internal resistance increases while the chargeable battery is being charged;

outputting a determination result of the abnormality; and

after determining that the abnormality has occurred, determining that the abnormality has been resolved if a value obtained by dividing a value of the internal resistance at a certain time point at or after a point in time when the abnormality has occurred in the chargeable battery by a maximum value of the internal resistance at or after the point in time when the abnormality has occurred falls below a predetermined threshold value.