Determination device relating to plurality of batteries, electricity storage system, determination method and non-transitory storage medium

1. A determination device relating to a plurality of batteries which are connected in series, comprising:

a processor configured to determine a deterioration variance among the batteries, based on first voltage data indicative of a maximum voltage which is greatest among voltages of the batteries in each of measurements in a plurality of periods in charge or discharge of the batteries, and second voltage data indicative of a minimum voltage which is least among the voltages of the batteries in each of the measurements in the periods,

wherein the processor is configured to:

estimate a first internal state parameter as an internal state of the battery as an elemental battery, the first internal state parameter being based on a variation of the maximum voltage in the first voltage data;

estimate a second internal state parameter as an internal state of the battery as the elemental battery, the second internal state parameter being based on a variation of the minimum voltage in the second voltage data;

determine the deterioration variance among the batteries, based on at least the first internal state parameter and the second internal state parameter;

estimate a third internal state parameter indicative of an internal state in an entirety of a series-connected part of the batteries, based on at least third voltage data indicative of a voltage of the series-connected part of the batteries in each of the measurements in the periods in the charge or the discharge of the batteries; and

determine the deterioration variance among the batteries by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.

2. The determination device of claim 1 , wherein the processor is configured to determine the deterioration variance among the batteries by comparing the first internal state parameter and the second internal state parameter.

3. The determination device of claim 2 , wherein the processor is configured to determine that the deterioration variance among the batteries is greater as a difference between the first internal state parameter and the second internal state parameter becomes greater.

4. The determination device of claim 1 , wherein the processor is configured to determine a deterioration degree in an entirety of a series-connected part of the batteries, based on third voltage data indicative of a voltage of the series-connected part of the batteries in each of the measurements in the periods in the charge or the discharge of the batteries.

5. The determination device of claim 4 , wherein the processor is configured to: determine the deterioration degree in the entirety of the series-connected part of the batteries, based on at least the third internal state parameter.

6. An electricity storage system comprising:

the determination device of claim 1 ; and

the plurality of batteries connected in series,

wherein the processor of the determination device being configured to determine the deterioration variance among the batteries.

7. The electricity storage system of claim 6 , further comprising a measuring circuit configured to periodically measure the voltage of each of the batteries in each of the measurements in the periods in the charge or the discharge of the batteries,

wherein the first voltage data and the second voltage data are generated based on at least a measurement result of the voltage of each of the batteries in the measuring circuit.

8. The electricity storage system of claim 6 , wherein

each of the batteries includes a plurality of unit cells, and

the unit cells are connected in parallel in each of the batteries.

9. A determination method relating to a plurality of batteries which are connected in series, comprising:

determining a deterioration variance among the batteries, based on first voltage data indicative of a maximum voltage which is greatest among voltages of the batteries in each of measurements in a plurality of periods in charge or discharge of the batteries, and second voltage data indicative of a minimum voltage which is least among the voltages of the batteries in each of the measurements in the periods,

wherein the determining the deterioration variance comprising:

estimating a first internal state parameter as an internal state of the battery as an elemental battery, the first internal state parameter being based on a variation of the maximum voltage in the first voltage data;

estimating a second internal state parameter as an internal state of the battery as the elemental battery, the second internal state parameter being based on a variation of the minimum voltage in the second voltage data;

determining the deterioration variance among the batteries, based on at least the first internal state parameter and the second internal state parameter;

estimating a third internal state parameter indicative of an internal state in an entirety of a series-connected part of the batteries, based on at least third voltage data indicative of a voltage of the series-connected part of the batteries in each of the measurements in the periods in the charge or the discharge of the batteries; and

determining the deterioration variance among the batteries by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.

10. A non-transitory storage medium storing a determination program relating to a plurality of batteries which are connected in series, the determination program causing a computer to implement:

determining a deterioration variance among the batteries, based on first voltage data indicative of a maximum voltage which is greatest among voltages of the batteries in each of measurements in a plurality of periods in charge or discharge of the batteries, and second voltage data indicative of a minimum voltage which is least among the voltages of the batteries in each of the measurements in the periods,

wherein the determining the deterioration variance comprising:

estimating a first internal state parameter as an internal state of the battery as an elemental battery, the first internal state parameter being based on a variation of the maximum voltage in the first voltage data;

estimating a second internal state parameter as an internal state of the battery as the elemental battery, the second internal state parameter being based on a variation of the minimum voltage in the second voltage data;

determining the deterioration variance among the batteries, based on at least the first internal state parameter and the second internal state parameter;

estimating a third internal state parameter indicative of an internal state in an entirety of a series-connected part of the batteries, based on at least third voltage data indicative of a voltage of the series-connected part of the batteries in each of the measurements in the periods in the charge or the discharge of the batteries; and

determining the deterioration variance among the batteries by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.