Method for determining the capacity of a battery cell

摘要

The invention relates to a method for determining the capacity of a battery cell. A battery cell current I is measured during a measurement period, and an open terminal voltage UOCV1,UOCV2 of the battery cell is measured at the beginning and end of the measuring period. The method has the steps of ascertaining a total battery cell current Iges from the measured battery cell current I, ascertaining charge states SOC1, SOC2 at the beginning and end of the measurement period using the measured open terminal voltage UOCV1,UOCV2, ascertaining an estimated value of the capacity Qest using the total battery cell current Iges and a difference between the charge states SOC1, SOC2, ascertaining a total measurement error of the estimated value of the capacity Qest from measurement errors of the total battery cell current Iges and the charge states SOC1, SOC2, and ascertaining a new value of the capacity Qnew using a known value of the capacity Qact, the estimated value of the capacity Q, and the total measurement error. The new value of the capacity Qnew is in a monotonic relationship with the known value of the capacity Qact and the estimated value of the capacity Qest such that the new value of the capacity Qnew is determined more strongly from the estimated value of the capacity Qest in the case of at least one first value of the total measurement error than in the case of at least one second value of the total measurement error, said second value lying above the at least one first value, and the new value of the capacity Qnew is determined less strongly from the known value of the capacity Qest in the case of the first value of the value of the total measurement error than in the case of the second value of the total measurement error. The invention further relates to a computer program, a battery management system (2), and a motor vehicle which are designed to carry out the method.

主权项

1. A method for determining the capacity of a battery cell, wherein a battery cell current I is measured during a measurement time period and an open circuit voltage UOCV1, UOCV2 of the battery cell is measured at the beginning and end of the measurement time period, the method comprising:
a) determining, by a battery management system (2), a total battery cell current Itot from the measured battery cell current I, b) determining, by the battery management system (2), states of charge SOC1, SOC2 at the beginning and at the end of the measurement time period on the basis of the measured open circuit voltage UOCV1, UOCV2, c) determining, by the battery management system (2), an estimated value of the capacity Qest on the basis of the total battery cell current Itot and a difference between the states of charge SOC1, SOC2, d) determining, by the battery management system (2), a total measurement errorΔ⁢⁢QQof the estimated value of the capacity Qest from measurement errors of the total battery cell current Itot and the states of charge SOC1, SOC2,
e) determining, by the battery management system (2), a new value of the capacity Qnew on the basis of a known value of the capacity Qact, the estimated value of the capacity Qest and the total measurement errorΔ⁢⁢QQ, wherein the new value of the capacity Qnew is in a monotonic relationship with the known value of the capacity Qact and the estimated value of the capacity Qest such that
in the case of at least one first value of the total measurement errorΔ⁢⁢QQ the new value of the capacity Qnew is ascertained from the estimated value of the capacity Qest to a greater extent than in the case of at least one second value of the total measurement errorΔ⁢⁢QQ which lies above the at least one first value, andin the case of the first value of the total measurement errorΔ⁢⁢QQ the new value of the capacity Qnew is ascertained from the known value of the capacity Qact to a lesser extent than in the case of the second value of the total measurement errorΔ⁢⁢QQ; wherein the battery management system (2) uses the new value of the capacity Qnew to extend the life of the battery cell.