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Secondary battery degradation determination method and secondary battery degradation determination device

  • US 10,386,420 B2
  • Filed: 08/18/2015
  • Issued: 08/20/2019
  • Est. Priority Date: 02/19/2013
  • Status: Active Grant
First Claim
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1. A secondary battery degradation determination method comprising:

  • determining, with circuitry, a driving state of a vehicle provided with a secondary battery on the basis of a current value of the secondary battery;

    measuring, with the circuitry, an open-circuit voltage (OCV) of the secondary battery;

    detecting, with the circuitry, a current and a voltage between terminals while the secondary battery is being discharged and calculating internal resistance R of the secondary battery;

    when a predetermined load provided in the vehicle is operated with a discharge current equal to or greater than a predetermined value, detecting, with the circuitry, a maximum discharge current value Inew which is a maximum value of the discharge current;

    comparing, with the circuitry, the detected maximum discharge current value Inew with a stored maximum discharge current value Is, updating, with the circuitry, the maximum discharge current value Is to a larger of the two maximum discharge current values, and storing, with the circuitry, the updated maximum discharge current value;

    detecting, with the circuitry, a temperature of the secondary battery;

    estimating, with the circuitry, a state of charge of the secondary battery;

    correcting, with the circuitry, the internal resistance R1 to internal resistance R1c at a predetermined reference temperature, on the basis of the state of charge and the temperature of the secondary battery, 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;

    calculating, with the circuitry, a minimum voltage Vs of the secondary battery when the load is operated based on the following expression;


    Vs=OCV−

    R1

    Is
    using the open-circuit voltage OCV, the corrected internal resistance R1c, and the maximum discharge current value Is;

    determining, using the circuitry, 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; and

    outputting, by the circuitry, a notification to a user of the vehicle that the secondary battery has degraded based on the determination by the circuitry that the secondary battery has degraded.

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