State of charge

About: State of charge is a research topic. Over the lifetime, 12013 publications have been published within this topic receiving 201419 citations. The topic is also known as: SoC & SOC.

State-of-Charge and State-of-Health Lithium-Ion Batteries’ Diagnosis According to Surface Temperature Variation

Abstract: This paper presents a hybrid state-of-charge (SOC) and state-of-health (SOH) estimation technique for lithium-ion batteries according to surface temperature variation (STV). The hybrid approach uses an adaptive observer to estimate the SOH while an extended Kalman filter (EKF) is used to predict the SOC. Unlike other estimation methods, the closed-loop estimation strategy takes into account the STV and its stability is guaranteed by Lyapunov direct method. In order to validate the proposed method, experiments have been carried out under different operating temperature conditions and various discharge currents. Results highlight the effectiveness of the approach in estimating SOC and SOH for different aging conditions.

Driving force control system for automotive vehicle

Abstract: A driving force control system for an automotive vehicle using driving torque produced by at least one of an internal combustion engine and an electric motor for propulsion, and including a battery and a power-transmission mechanism having a continuously variable transmission, comprises sensors detecting vehicle speed, engine speed, an accelerator operating amount, a state of charge of the battery. An electronic control unit calculates a target engine speed needed to realize the vehicle speed, the target driving torque and the target generated electric energy at the lowest fuel consumption, considering an efficiency of each of the engine, the electric motor, and the power-transmission mechanism, so as to operate the engine, the electric motor, and/or the power-transmission mechanism always at their optimum operating points depending on the ratio of a first time rate of doing work for the driver's required driving torque to a second time rate of doing work for the required generated electric energy, as well as the sum of the first and second time rates.

Estimation of state of health of lithium-ion batteries based on charge transfer resistance considering different temperature and state of charge

Abstract: State of health diagnosis and estimation of lithium-ion batteries is a key feature of an advanced battery management system. Electrochemical impedance spectroscopy is frequently used for the state of health diagnosis and estimation. In the paper, the charge transfer resistance of the battery is obtained by fitting the impedance spectroscopy with an equivalent impedance model to estimate state of health. And an analytical calculation model with temperature and state of charge as inputs is derived and verified considering their effect on the charge transfer resistance. With the calculation model, the charge transfer resistance at randomly selected state of charge and temperature is converted to the standard state to be comparable for the state of health estimation. It is indicated that state of health estimated with the converted and the direct fitted charge transfer resistance agree well. The battery state of health estimation method with the converted charge transfer resistance eliminates the need to specifically control the temperature and state of charge during the impedance spectrum measurement. It benefits the practical application of the state of health estimation with electrochemical impedance spectroscopy.

Modeling Battery Behavior for Accurate State-of-Charge Indication

Abstract: Li-ion is the most commonly used battery chemistry in portable applications nowadays. Accurate state-of-charge (SOC) and remaining run-time indication for portable devices is important for the user's convenience and to prolong the lifetime of batteries. A new SOC indication system, combining the electromotive force (EMF) measurement during equilibrium and current measurement and integration during charge and discharge, has been developed and implemented in a laboratory setup. During discharge, apart from simple Coulomb counting, the effect of the overpotential is also considered. Mathematical models describing the EMF and the overpotential functions for a Li-ion battery have been developed. These models include a variety of parameters whose values depend on the determination method and experimental conditions. In this paper the battery measurement and modeling efforts are described. The method of implementing the battery model in an SOC indication system is also described. The aim is an SOC determination within 1% inaccuracy or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. The achieved results show the effectiveness of our novel approach for improving the accuracy of the SOC indication.