Study on a High-Accuracy Real-Time Algorithm to Estimate SOC of Multiple Battery Cells Simultaneously

Abstract

In traditional battery equalization strategy, open-circuit voltage (OCV) of battery cells was used to judge the difference of SOC between them. However, OCV is not only determined by SOC but also influenced by internal resistance, polarization voltage, capacity, and other nonlinear factors. As a result, OCV is not an ideal indicator of SOC differences, especially in transient conditions. In order to control battery consistency accurately, it is best to use SOC directly as standard for battery consistency judgment and control. To achieve this, an algorithm that can estimate SOC of multiple battery cells simultaneously with low computational complexity and high accuracy is needed. Limited by computing speed of Battery Control Unit (BCU), existing SOC estimation method is hard to estimate SOC of each battery cell simultaneously with high accuracy. In this research, a new SOC estimation strategy was proposed to estimate SOC of multiple battery cells simultaneously for battery equalization control. Battery model is established based on experimental data, and a processor-in-the-loop test system was established to verify the actual performance of the proposed algorithm. Results of simulation and test indicate that the proposed algorithm can estimate SOC of multiple battery cells simultaneously and achieved good real-time performance and high accuracy.

Parameter Identification and State Estimation of Lithium-Ion Batteries for Electric Vehicles with Vibration and Temperature Dynamics

“…However, the ECM is costly and time-consuming, and it is impractical to obtain all parameters as the ECM model parameters can only be parameterized accurately for a few batteries. However, if the model order increases, i.e., the first-order ECM is employed, it can improve the time precision [18] to some level due to its fewer matrix dimensions but with higher time efficiency, at the same time, if second-order ECM is employed, lower time efficiency [21] with higher accuracy of SOC estimation is yielded. A simple ECM, which guarantees high accuracy but less time efficiency, that is considered in this paper consists of the equivalent ohmic resistor Ro, the resistance-capacitance (RC) network with Rp as the equivalent polarization resistance, and Cp is the equivalent polarization capacitance, which is used to simulate transient responses of the LIB during the charge-discharge operation, and the open-circuit voltage Uocv.…”

Toward Group Applications of Zinc-Silver Battery: A Classification Strategy Based on PSO-LSSVM

“…will be amplified due to continuous charge and discharge cycle, which not only affects correctly judging the state of health(SOH) or the state of charge(SOC) of the battery pack, but also evoke the capacity attenuation and lifetime decay of the battery pack, and even leads to safety and reliability issues [4], [5]. Therefore, an optimal battery group strategy is particularly necessary [6].…”