An Improved Equivalent Circuit Parameter Representation of Lithium Ion Batteries Using Electrochemical Model Based Approach

Lithium ion batteries are the primary source of power for most of the consumer electronics today. Estimation of State-of-Charge (SOC), an indicator of available charge in a battery, is vital to determine available operational time of the device. SOC is crucial to estimate the available range in an electric vehicle. Most calculations involving batteries use an equivalent circuit lumped model for calculation purposes, these models are inaccurate as they do not capture the complete electrochemical dynamics of the cell. In this paper we employ Single Particle Model which considers electrolyte behaviour while estimating equivalent circuit parameters. The proposed approach improves SOC estimation accuracy while reducing computational complexity. The electrochemical model used in this approach takes into account two spherically symmetric diffusion equations: one within a representative negative particle ($\mathrm{k}=\mathrm{n}$) and one within a representative positive particle ($\mathrm{k}=\mathrm{p}$) including electrolyte equations.