Cycling degradation testing and analysis of a LiFePO₄ battery at actual conditions

Abstract

Summary This paper presents a degradation testing of a lithium‐ion battery developed using real world drive cycles obtained from an electric vehicle (EV). For this, a data logger was installed in the EV, and real world drive cycle data were collected. The EV battery system consists of 3 lithium‐ion battery packs with a total of 20 battery modules in series. Each module contains 6 series by 49 parallel lithium‐ion cells. The vehicle was driven in the province of Ontario, Canada, and several drive cycles were recorded over a 3‐month period. However, only 4 drive cycles with statistical analysis are reported in this paper. The reported drive cycles consist of different modes: acceleration, constant speed, and deceleration in both highway and city driving at −6°C, 2°C, 10°C, and 23°C ambient temperatures with all accessories on. Additionally, individual cell characterization was conducted using a C/25 (0.8A) charge‐discharge cycle and hybrid pulse power characterization (HPPC). The Thevenin battery model was constructed in MATLAB along with an empirical degradation model and validated in terms of voltage and SOC for all drive cycles reported. The presented model closely estimated the profiles observed in the experimental data. Data collected from the drive cycles showed that a 4.6% capacity fade occurred over the 3 months of driving. The empirical degradation model was fitted to these data, and an extrapolation estimated that 20% capacity fade would occur after 900 daily drive cycles.

Detection Method for Soft Internal Short Circuit in Lithium-Ion Battery Pack by Extracting Open Circuit Voltage of Faulted Cell

“…Although in this study the proposed method focused on detecting the soft ISCr at constant temperature, depending on real applications the ambient temperature can be changed [58]. Therefore, detection of ISCr in the battery under varing ambient temperature is a maningful and interesting subject of reaserch as a future work.…”

Exploring the Effect of Increased Energy Density on the Environmental Impacts of Traction Batteries: A Comparison of Energy Optimized Lithium-Ion and Lithium-Sulfur Batteries for Mobility Applications

“…LIBs have been widely adopted and currently dominate both portable electronic devices and the electric vehicle market [8]. Among the different LIB technologies available, NMC-type layered oxides (LiNi 1−x−y Mn y Co x O 2 ) are one of the most established positive electrode material in EVs as is evaluated in [12][13][14][15][16]. Research towards the improvement of NMC cathode materials have focused on the optimization of its specific energy by both increasing the amount of nickel and lithium within the cathode slurry [9].…”

Online Parameter Identification and State of Charge Estimation of Lithium-Ion Batteries Based on Forgetting Factor Recursive Least Squares and Nonlinear Kalman Filter

“…The Thevenin model, which is also called first-order resistor-capacitor (RC) equivalent circuit model, is often used for lithium-ion battery modeling and analysis [38,39]. In this article, the Thevenin model is used as battery model.…”