Abstract
In electric vehicle (EV) and hybrid electric vehicle (HEV) application, accurate information of state-ofcharge (SOC) and capacity of each cell are required for elaborate SOC/capacity estimation algorithm of the battery pack. However, the measurement of the states of all cells using sophisticated algorithms increases the computation time beyond practicality, because the computation time required for the SOC/capacity estimation of the battery pack is directly affected by the number of unit cells. In this work, a simple SOC and capacity estimation algorithm for Li-ion battery pack is newly proposed by using filtered terminal voltage. The SOC estimation algorithm using filtered terminal voltage extracts an estimated current information from the terminal voltage of the battery pack through equivalent-circuit model (ECM)-based filters without sensing the current. Consequently, it drastically reduces computational steps for the SOC estimation algorithm. With the fact that all the current flowing through the series-connected cells in pack are identical, the estimated current value of each cell should be identical. As a result, it can be known that this algorithm enables us to obtain the relative proportion of SOC/capacity information of each cells and battery pack with minimal complexity increase. To validate the performance of the proposed approach, a scaled-down HEV profile is used for a pack consists of twelve 18650 series-connected Li-ion batteries (12S1P). The experimental results verify the performance of the proposed battery pack SOC estimation algorithm.
Highlights
In order to achieve the state-of-charge (SOC) and capacity estimation of a series-cell configured battery pack, information on average value of cell voltages and pack current is widely used
Numerous works have been studied in order to achieve correct SOC/capacity estimation of battery pack using each cell’s voltage and capacity information [1]
These works have an inevitable drawback of increased computation time required for SOC/capacity estimation due to constructing sophisticated algorithms that can measure all cell’s states
Summary
In order to achieve the state-of-charge (SOC) and capacity estimation of a series-cell configured battery pack, information on average value of cell voltages and pack current is widely used. It assumes that electrochemical characteristics of all cells are approximately identical. Numerous works have been studied in order to achieve correct SOC/capacity estimation of battery pack using each cell’s voltage and capacity information [1]. This work present a new method that uses information on filtered terminal voltage for SOC/capacity estimation without using cell current information [2] This drastically reduces the computation time and robustness against difference among cell’s parameter. Experimental results for SOC/capacity estimation of cells and a series-cell configured battery pack are shown for verification of this work
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