SECONDARY BATTERY DEGRADATION DETERMINATION METHOD AND SECONDARY BATTERY DEGRADATION DETERMINATION DEVICE

摘要

Provided are a secondary battery degradation determination method and a secondary battery degradation determination device which can detect degradation of a secondary battery in advance even before an engine starts. When it is determined in Step S1 that a vehicle is in a stop state, a stable-state open-circuit voltage OCV is measured in Step S2 and internal resistance R1 is calculated in Steps S3 and S4. On the other hand, when it is determined in Step S1 that a starter 21 is operated, a maximum discharge current value Inew is measured in Step S5 and a maximum discharge current value Is is updated in Steps S6 and S7. In Step S14, a minimum voltage Vs is calculated. In Step S15, the stable-state open-circuit voltage OCV and the minimum voltage Vs are compared with predetermined threshold values to perform the degradation determination of a secondary battery 10.

主权项

1. A secondary battery degradation determination method comprising:
a driving state determination step of determining a driving state of a vehicle provided with a secondary battery on the basis of a current value of the secondary battery; an open-circuit voltage measurement step of measuring an open-circuit voltage OCV of the secondary battery; an internal resistance calculation step of detecting a current and a voltage between terminals while the secondary battery is being discharged and calculating internal resistance R1 of the secondary battery; a maximum current detection step of, when a predetermined load provided in the vehicle is operated with a discharge current equal to or greater than a predetermined value, detecting a maximum discharge current value Inew which is a maximum value of the discharge current; a maximum current update step of comparing the detected maximum discharge current value Inew with a stored maximum discharge current value Is, updating the maximum discharge current value Is to the larger of the two maximum discharge current values, and storing the updated maximum discharge current value; a temperature detection step of detecting a temperature of the secondary battery; a state-of-charge estimation step of estimating a state of charge of the secondary battery; an internal resistance correction step of correcting the internal resistance R1 to internal resistance R1c at a predetermined reference temperature, on the basis of the state of charge estimated in the state-of-charge estimation step and the temperature detected in the temperature detection step, using a table or a relational expression which is made in advance to indicate a relation between the internal resistance and the state of charge and temperature of the secondary battery; a minimum voltage calculation step of calculating a minimum voltage Vs of the secondary battery when the load is operated based on the following expression:
Vs=OCV−R1c×Is using the open-circuit voltage OCV, the corrected internal resistance R1c, and the maximum discharge current value Is; and
a degradation determination step of determining that the secondary battery has degraded when the open-circuit voltage OCV is equal to or greater than a first threshold value and the minimum voltage Vs is less than a second threshold value.