Relaxation model of the open‐circuit voltage for state‐of‐charge estimation in lithium‐ion batteries

Abstract

The open-circuit voltage (OCV) of batteries is a crucial characteristic parameter that reflects many aspects of a battery's performance, such as capacity, state-of-charge (SOC) and state-of-health. OCV is most widely used to determine the SOC when the battery works in a charge-depleting state. However, the application of the OCV to SOC estimation can be difficult because of the need for a long rest time for full relaxation. In this study, based on the analysis on the curve shape of battery voltage relaxation, a new adaptive model for simulating the voltage relaxation process is developed to predict the final static OCV in a few minutes instead of via the traditional long-term rest method. Avoiding this disadvantage, the SOC can be deduced from the predicted OCV via the corresponding relationship obtained in a short amount of time. A working condition experiment is performed to validate the new methods and the results are very accurate.

Kalman filter Observer for SoC prediction of Lithium cells

“…It is applied in science fields like bioengeneering [29], electronics [30,31] and control theory [32]. In addition, almost engineer applications have focused on FOC startegies which are based generally on describing the aspects of dynamic systems by condensed expressions and considering non local characteristics such as thermal diffusion phenomenon [33] and botanical electrical impedances [34].…”

State of Charge Estimation for Electric Vehicle Battery Based on Amended Ah Metrology

“…In [3], an adaptive model for simulating the voltage relaxation process is developed to predict the final static open-circuit voltage in a few minutes. Other model-based method with filter algorithm, such as extend Kalman filter, is introduced in this field to improve the accuracy of SOC estimationsby removing measurement noise [4].…”

An integrated approach for real-time model-based state-of-charge estimation of lithium-ion batteries

“…OCV in real-time [19]. Another problem is that the LiFePo4 battery used in this experiment shows a very flat OCV-SOC curve during two SOC segments, one from 70% to 90% SOC and another from 30% to 50% SOC, as shown in However, Electrochemical models are very complex and involve partial differential equations which are difficult to solve and analyse for real-time purposes.…”