US 11,714,135 B2
Method for determining the capacity of Li-ion cells with the aid of distinct points
Dorothea Kalin, Munich (DE); and Christian Röttinger, Ingolstadt (DE)
Assigned to AUDI AG, Ingolstadt (DE)
Filed by AUDI AG, Ingolstadt (DE)
Filed on Aug. 23, 2021, as Appl. No. 17/409,603.
Claims priority of application No. 102020122111.8 (DE), filed on Aug. 25, 2020.
Prior Publication US 2022/0065938 A1, Mar. 3, 2022
Int. Cl. G01R 31/388 (2019.01); H02J 7/00 (2006.01)
CPC G01R 31/388 (2019.01) [H02J 7/0048 (2020.01)] 12 Claims
OG exemplary drawing
 
1. A method for determining a capacity of at least one lithium-ion cell, during open circuit voltage aging with the aid of at least one distinct point in at least one voltage curve during a charging process or in at least one open circuit voltage of the lithium-ion cell, comprising:
measuring the at least one open circuit voltage of the lithium-ion cell or measuring the at least one voltage curve of the lithium-ion cell during the charging process of the lithium-ion cell;
detecting the at least one distinct point of the at least one open circuit voltage of the lithium-ion cell or of the at least one voltage curve of the lithium-ion cell during the charging process when a second derivative of the at least one open circuit voltage or of the at least one voltage curve of the lithium-ion cell changes with respect to time;
checking a shift of the at least one distinct point in at least one of the at least one open circuit voltage of the lithium-ion cell and the at least one voltage curve of the lithium-ion cell due to open circuit voltage aging;
ascertaining the at least one distinct point in the open circuit voltage of the lithium-ion cell or in the voltage curve of the lithium-ion cell when a non-shift of the distinct point has been checked; and
using the at least one distinct point as a state of charge reference point.