Smart and accurate state-of-charge indication in portable applications

Accurate state-of-charge (SoC) and remaining run-time indication for portable devices is important for the user-convenience and to prolong the lifetime of batteries. However, the known methods of SoC indication in portable applications are not accurate enough under all practical conditions. The method presented in this paper aims at designing and testing an SoC indication system capable of predicting the remaining capacity of the battery and the remaining run-time with an accuracy of 1 minute or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. At the moment Li-ion is the most commonly used battery chemistry in portable applications. Therefore, the focus is on SoC indication for Li-ion batteries. The basis of the proposed algorithm is current measurement and integration during charge and discharge state and voltage measurement during equilibrium state. Experimental results show the effectiveness of the presented novel approach for improving the accuracy of the SoC indication