Uncertainty analysis in a real-time state-of-charge evaluation system for lithium-ion batteries

Lithium-ion (Li-ion) is the most commonly used battery chemistry in portable applications nowadays. Accurate State-of-Charge (SoC) and remaining run-time (tr) calculation for portable devices is important for the user convenience and to prolong the lifetime of batteries. A new SoC algorithm for Li-ion batteries that combines adaptivity with direct measurement and book-keeping systems has been developed and implemented in a real-time evaluation system. In this paper the error sources in the real-time SoC evaluation system with possible calibration solutions are described. The goal of the SoC system is to predict the remaining run-time of a Li-ion battery with an uncertainty of 1 minute or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range.