Lithium battery charge state estimation method, battery management system and battery system

A lithium battery charge state estimation method includes the following steps that an initial electric quantity value of a lithium battery is acquired; based on the initial electric quantity value, the current electric quantity of the lithium battery is preliminarily estimated according to the ampere-hour method; battery circuit model parameters of the lithium battery are corrected according to the recursive least-squares method; based on the preliminarily-corrected battery circuit model parameters, the estimated current electric quantity of the lithium battery is further corrected according to the extended Kalman filtering method. The invention further provides a battery management system and a battery system which adopt the lithium battery charge state estimation method.