Abstract
Research/Objective
During driving the vehicle lithium ion battery pack voltage and current are constantly varied due to the charging and discharging repetitions which affect the available power of the battery pack to the electric motor. The use of previous method, there is limit to the error occurrence and system implementation. The objective of this study was to estimate SOC using battery power and internal resistance.
Methodology
In this study battery power and internal resistance considered SOC estimation method is investigated by applying the simplified impedance modeling, which draws battery actual available power from the calculation of power applied to the load and internal resistance during charging and discharging for the accurate SOC estimation. That is to say the consideration of battery hysteresis characteristic and energy loss by internal resistance. Battery pack SOC estimation algorithm is designed out by MATLAB SIMULINK. Simulation and battery system test condition were applied current mode (UDDS, HWFET) compatible with battery system. Vehicle test was also carried by driver’s actual situation.
Results
The novel SOC estimation method shows 3% error under UDDS and HEFET drive cycle at various temperatures. Vehicle test also showed the same results.
Limitations of this study
An important limitation of the current study is limited manganese-based lithium ion battery. The Lithium ion batteries including other active material are not yet verified. What does the paper offer that is new in the field including in comparison to other work by the authors? SOC estimation method applying power is different and new.
Conclusions
Power and simple resistance circuit were introduced resulting in reducing current sensor noise and reflecting relaxation effect of the battery for generating novel SOC estimation method.
Key Words - Lithium Ion Battery, State of Charge, Internal Resistance, Power Counting