Secondary battery system
A secondary battery system includes a secondary battery having an electrode body impregnated with an electrolytic solution containing metal ions. The secondary battery system measures an impedance of the secondary battery. The secondary battery system detects high-rate deterioration caused by uneven concentration of the metal ions in the electrolytic solution impregnated into the electrode body.
1 . A secondary battery system comprising:
a secondary battery having an electrode body impregnated with an electrolytic solution containing metal ions; and
at least one processor with a memory storing computer program code executable by the processor configured to cause the secondary battery system to implement:
an impedance measurement unit configured to measure an impedance of the secondary battery; and
a diagnosis unit configured to detect high-rate deterioration, which is caused by uneven concentration of the metal ions in the electrolytic solution impregnated into the electrode body, in the secondary battery based on an absolute value of a difference between a direct current (DC) resistance component and a reaction resistance component of the impedance measured by the impedance measurement unit during DC charging or discharging and the impedance measured by the impedance measurement unit after DC charging or discharging has stopped,
wherein the diagnosis unit determines that high-rate deterioration has occurred in the secondary battery when the absolute value of the difference exceeds a predetermined reference value.
2 . The secondary battery system according to claim 1 , wherein
an average value of a direct current flowing through the secondary battery in a section of equal to or longer than 10 minutes is equal to or greater than 0.2 C of a battery capacity.
3 . The secondary battery system according to claim 1 , wherein
the diagnosis unit corrects the impedance measured by the impedance measurement unit to an impedance corresponding to a predetermined temperature and a predetermined state of charge (SOC).
4 . The secondary battery system according to claim 1 , wherein the at least one processor is further configured to cause the secondary battery system to implement:
a charge or discharge control unit configured to perform control for suppressing a charge or discharge current of the secondary battery when a difference between resistance during DC charge or discharge of the secondary battery and resistance during absence of energization of the secondary battery is larger than a predetermined value.
5 . The secondary battery system according to claim 1 , wherein
the impedance measurement unit uses, as a frequency for measuring the impedance during DC charging or discharging of the secondary battery, a frequency different from a frequency of an alternating current (AC) signal component included in a direct current for charging or discharging the secondary battery and a frequency of a harmonic component included in the AC signal component.
6 . The secondary battery system according to claim 1 , wherein
in measuring the impedance during DC charging or discharging of the secondary battery, the impedance measurement unit adjusts modulated current used for measuring the impedance such that a current ratio between the modulated current and an external current having a same frequency as a frequency of the modulated current or a frequency of a harmonic component included in the modulated current, or an external current having an alternating current (AC) signal component included in a direct current to be charged and discharged is equal to or less than a threshold.
7 . A secondary battery system comprising:
a secondary battery having an electrode body impregnated with an electrolytic solution containing metal ions; and
at least one processor configured to
measure an impedance of the secondary battery, and
detect high-rate deterioration, which is caused by uneven concentration of the metal ions in the electrolytic solution impregnated into the electrode body, in the secondary battery based on an absolute value of a difference between a direct current (DC) resistance component and a reaction resistance component of the impedance during DC charging or discharging and the impedance after DC charging or discharging has stopped,
wherein the at least one processor determines that high-rate deterioration has occurred in the secondary battery when the absolute value of the difference exceeds a predetermined reference value.