Quality decision for overcharged li-ion battery from reliability and safety perspective

During charging of Lithium-ion battery (LiB), the charging cutoff voltage (COV) may exceed the manufacturers' specification because of incorrect monitoring of the charging control circuit, either due to the aging of the control circuit or the design/manufacturing errors of the control circuit. In fact, it is found that overcharging LiB cell is a common abuse. This work shows the effect of excessive COV on cell's discharging ability, and the use of a novel nondestructive method to evaluate if the damage made in the cell by the excessive COV is rendering the cell from further safe usage or it is still acceptable with minor degradation in reliability and safety, thus providing a basis for quality consideration of the cell. The method also enables battery manufacturers to identify the internal components for their cells that are most vulnerable to the excessive COV so that quality improvement of their batteries can be designed and produced. This method also alerts electric vehicles user on the hidden safety issues of their battery pack, and enables battery management system to perform reliability balancing, a new patented technique to ensure the safe and reliable operation of battery pack.