Framework for energy storage selection to design the next generation of electrified military vehicles

Abstract

Abstract Lithium-ion batteries (LIBs) are being used as the chemistry of choice across all the electrified vehicles. However, when vehicle load requirements, driving cycle missions and operating conditions vary across a wide range of opportunities, such a selection might not lead to satisfactory performance. This is the case of military vehicle (MV) applications. The objective of this paper is to develop a methodology aimed at determining the most suitable energy storage system (ESS) for a targeted vehicle/application. The proposed design framework is centered on the Enhanced-Ragone plot (ERp) as a tool to guide the selection strategy. The ERp is an experimentally-built tool that maps on the specific power and energy log-log plane the performance of three different LIB chemistry as a function of C-rate, temperature, and supercapacitors (SC). From the vehicle side, a backward simulator of an hybrid powertrain - composed with internal combustion engine (ICE), battery and SC - is developed and used to compute the power profile at the wheel. Then, a segmentation procedure is implement as energy management strategy to assign low, medium and high frequency contents to ICE, battery and SC from which the requested power-to-energy ratio for each ESS is then calculated. The matching algorithm ensures that the selected ESS (either in the battery standalone configuration or hybrid solution) satisfies both power and energy vehicle requirements. Moreover, sizing - in terms of pack weight, volume, number of cells and energy - is studied. We validate the matching design algorithm on three vehicles - Tesla model S, Tesla Semi truck and high mobility multipurpose wheeled vehicle - tested over energy consumption and power consumption tests (namely, range and acceleration tests), UDDS and US06 time-dependent driving cycles, and Harford distance dependent grade military drive cycle. Results point out that the aggressiveness of the cycle determines whether the SC is recommended or not, and which battery chemistry is the most suitable one.