A gas-liquid dynamic model-based accurate
lithium-
ion battery SOC
estimation method, the gas-liquid dynamic model being a cylindrical closed container, a
pipe and a valve that can be opened or closed being mounted at the top of the container, a liquid having a volume of Vw being held in the cylindrical container, and the remaining volume, V, being the volume of a gas having a pressure of P. According to the accurate SOC
estimation method, a model, different from conventional RC
equivalent circuit model and electrochemical model, is established from the perspective of a gas-liquid coexistence
system. The method comprises the following steps: setting up an
ideal gas state equation, a gas continuous motion equation, a gas-liquid
dissolution equilibrium equation, etc. according to a gas-liquid coexistence
system model; deriving
steady state and
transient state recursion formula of the gas-liquid coexistence
system according to the model equations; performing intermittent charging and discharging stationary test on a certain model of battery; and fitting the expression of the relation between SOC and
open circuit voltage, and recognizing parameter values of the gas-liquid coexistence
system model, so as to achieve online
estimation of a battery SOC value. The
recursion formula is simple, has self-convergence characteristics, and can accurately describe the nonlinear characteristics of the battery.