Lithium-ion battery as an efficient, sustainable, and clean energy for electric vehicles (EVs) and smart devices becomes more popular with the worldwide demand for reduction of greenhouse gas emission. In all kinds of applications, an accurate real-time estimation for state of charge (SOC) of battery is necessary. Some conventional methods usually need to sample both battery currents and voltages. This article presents a novel SOC estimation algorithm without current detection. This algorithm just acquires the port voltages of cell to calculate the open-circuit voltage (OCV) which is related to SOC. By extracting a large number of battery voltages based on a step response, some important parameters that can track battery working process are determined. In order to verify the algorithm feasibility and accuracy, it has been tested on a commercial common field-programmable gate array (FPGA) in different application conditions. The algorithm accuracy is mainly limited by model accuracy and sampling sensor accuracy. The maximum error between ideal SOC and calculated SOC by this algorithm is within 4%, and the mean error is about 0.99%. So, this high-feasibility, accredited accuracy, easy integration, and low-cost solution has bright potential in smarter future.

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In order to cut the costs and overcome the leakage current of batteries caused in traditional method, this study introduces an improved voltage transfer method for lithium battery string management chip. This proposed circuit based on the improved voltage transfer method is fabricated in 180-nm Bipolar-CMOS-DMOS is correct technology, and has been successfully applied to a three lithium batteries string management chip. These measurements indicate that this circuit transfers each cell's voltage reliably and adopt protection against abnormal conditions. Furthermore, analysis of 50 samples shows that the improved method can greatly eliminate the battery leakage. The circuit reduces the leakage current to nanoampere scale and is integrated into the lithium battery string management chip, which is helpful for battery voltage balance and low cost.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.