16-032 Battery Paramenters/SOC Co-estimation Algorithm

January 10, 2016

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Authors

Abstract

This software is the implementation of the battery parameters/SOC co-estimation algorithm (Invention disclosure
13-099) in microcontroller-based platform. This algorithm uses the terminal voltage and current of the battery as input
signals. Considering a Resistor-Capacitor (RC) equivalent circuit to model the battery dynamics, the algorithm finds
the parameters of the battery model in real-time and updates the parameters when they change due to the changes in
temperature, C-rate and State of Charge (SOC). Moreover, the algorithm applies a piecewise linearization technique to
model the Open Circuit Voltage (OCV)-SOC curve in the battery which is inherently nonlinear. The piecewise
linearization uses linear system identification theory to estimate the battery model parameters without losing
accuracy.

Consequently, the program estimates the SOC of the battery based on the updating battery model with compensating
the initial estimate of the SOC. Also since the program takes the dynamics of the battery into account, it is not
sensitive to the voltage and current measurement noise. Moreover, since the full capacity of the battery degrades by
ageing effect, this algorithm is not based on the nominal full capacity assumption, and keeps the accuracy even when
the battery is aged.

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