For underwater vehicles, the state of charge (SOC) of
battery is
often used to guide the optimal allocation of energy. An accurate
SOC estimation can improve work efficiency and reliability of underwater
vehicles. Model-based SOC estimation methods are still mainstream
routes used in practical applications. Hence, accurate battery models
are highly desirable, which depends not only on the circuit structure
but also on the circuit parameters. Four-parameter identification
algorithms, offline mechanism-based and least squared (LS) methods,
as well as online recursive least-squares with forget factor (FFRLS)
and extended Kalman filter (EKF) methods were analyzed in terms of
SOC estimation under three different conditions. The results revealed
that in the case without any disturbance, the predicted SOCs based
on four-parameter identification circuits fitted well with the reference.
Moreover, it is remarkable that the LS offline methods work better
than the FFRLS online routes. In addition, the robustness has also
been accessed through the other two conditions, i.e., measurement
data with disturbance and initial SOC value with deviation. The results
showed that maximum errors of SOC estimation based on the EKF approach
are significantly lower than those of the other methods, and the values
are 0.51% and 0.20%, respectively. Thus, the circuit model based on
the EKF parameter identification approach possessed a stronger anti-interference
performance during the SOC estimation process. This research can provide
corresponding theoretical support on ECM parameter identification
for lithium-ion batteries in underwater vehicles.