The invention discloses an SOC 
estimation method based on an adaptive double extended Kalman filtering method. The SOC 
estimation method comprises the following steps: firstly, establishing a second-order RC 
equivalent circuit model of a 
lithium battery; then, determining open-circuit 
voltage and battery 
equivalent model parameters at different SOC (
state of charge) positions of the 
lithium battery through a pulse charging and discharging experiment; obtaining a function relationship between the open-circuit 
voltage and the SOC and relationships between other 
model parameters and different SOCs, the other 
model parameters including ohmic 
internal resistance, electrochemical polarization resistance, electrochemical polarization 
capacitance, concentration difference polarization resistance and concentration difference polarization 
capacitance values; establishing a 
state space equation taking the SOC and 
polarization voltage as state variables and a 
state space equation taking the ohmicinternal resistance as a 
state variable; and finally, performing iterative computation to obtain the SOC value of the 
lithium battery in real time. According to the method, the problem of unknown 
noise statistical characteristics in the prior art is solved, and meanwhile, the ohmic 
internal resistance of the battery is estimated by using the 
Kalman filtering algorithm, so that the model precisionis improved.