Abstract

International audience; This paper addresses the challenge of monitoring battery in fleets of electric vehicles (EV). The goal is to identify the different EV utilization modes, during real use, and to highlight the constraining conditions to manage battery health evolution. The other part of this study aims to build a battery capacity estimation model, permitting to estimate the remaining capacity of an EV during its real use. Finally, is explained a strategy to improve capacity estimates, based on the identified EV utilization modes.

Abstract

International audience; This study deals with the dynamic and thermal behaviors of supercapacitors. Characterization is performed using the Electrochemical Impedance Spectroscopy (EIS) method to determine by experiment the supercapacitor's series resistance (ESR) and capacitance according to the frequency. The study deals also the particular case of the supercapacitor's spectra and the thermal shock. Finally, life test at constant temperature and the impact of the vibration on the supercapacitor's parameters are illustrated.

Abstract

Electric vehicle battery performance near end-of-life is limited by mismatched cell degradation, leading to an estimated 5-10% cell capacity variation across the pack. Active cell balancing hardware architectures incorporating a Low-Voltage (LV) bus supply have been introduced to unlock lost capacity due to cell imbalance at reduced cost, through elimination of the vehicle's 400-to-12V dc-dc converter. In this work, a hierarchical model-predictive control scheme is applied to a time-shared isolated converter active balancing architecture that incorporates LV bus supply. The proposed controller efficiently divides computation among the battery management system hardware components. The energy-buffering capability of the lead-acid battery, which is connected to the LV bus, is used to trade-off balancing and bus regulation objectives, reducing peak power and improving the system cost-effectiveness. Simultaneous state-of-charge balancing and LV bus regulation is verified in simulation and experiment using real-world drive and LV load data collected from a GM Bolt electric vehicle. Similar controller performance compared to a central scheme is achieved in simulation. The experimental setup includes a custom 12S2P, 3.9kWh, liquid-cooled Lithium Nickel Manganese Cobalt battery module with embedded battery management system. The controller performance is evaluated with an initial maximum state-of-charge imbalance of 6.8%.

Abstract

In this paper, we demonstrate high spatial (≈3 cm) and spectral (≈30 MHz) resolution Brillouin sensing by use of Brillouin optical frequency-domain analysis (BOFDA) and signal processing. An iterative method is employed to correct the acquired data from spurious effects associated to acoustic wave modulation and relevant in the high spatial resolution regime. Experimental tests demonstrate that the proposed algorithm allows to reconstruct the Brillouin shift profile with the full spatial resolution allowed by the system bandwidth.