Citation: Földesi, P.; Kóczy, L.T.; Szauter, F.; Csikor, D.; Kocsis Szürke, S. Hierarchical Diagnostics and Risk Assessment for Energy Supply in Military Vehicles. Energies 2022, 15, 4791. https://doi.org/10.3390/ en15134791 Academic Editors: Amir Mosavi and Annamária R. Várkonyi-Kóczy Received: 24 May 2022 Accepted: 24 June 2022 Published: 29 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Hierarchical Diagnostics and Risk Assessment for Energy Supply in Military Vehicles Péter Földesi *, László T. Kóczy , Ferenc Szauter, Dániel Csikor and Szabolcs Kocsis Szürke Department of Logistics and Forwarding, Széchenyi István University, 9026 Gy˝ or, Hungary; koczy@sze.hu (L.T.K.); szauter@sze.hu (F.S.); csikor.daniel@ga.sze.hu (D.C.); kocsis.szabolcs@ga.sze.hu (S.K.S.) * Correspondence: foldesi@sze.hu Abstract: Hybrid vehicles are gaining increasing global prominence, especially in the military, where unexpected breakdowns or even power deficits are not only associated with greater expense but can also cost the lives of military personnel. In some cases, it is extremely important that all battery cells and modules deliver the specified amount of capacity. Therefore, it is recommended to introduce a new measurement line of rapid diagnostics before deployment, in addition to the usual procedures. Using the results of rapid testing, we recommend the introduction of a hierarchical three-step diagnostics and assessment procedure. In this procedure, the key factor is the building up of a hierarchical tree-structured fuzzy signature that expresses the partial interdependence or redundancy of the uncertain descriptors obtained from the rapid tests. The fuzzy signature structure has two main important components: the tree structure itself, and the aggregations assigned to the internal nodes. The fuzzy signatures that are thus determined synthesize the results from the regular maintenance data, as well as the effects of the previous operating conditions and the actual state of the battery under examination; a signature that is established this way can be evaluated by “executing the instructions” coded into the aggregations. Based on the single fuzzy membership degree calculated for the root of the signature, an overall decision can be made concerning the general condition of the batteries. Keywords: risk assessment; military vehicles; battery; energy supply 1. Introduction Lithium-based batteries are gaining ground with the proliferation of electric vehicles [1,2]. Today, Li-ion batteries can be found everywhere due to their reliability and high energy density, ranging from the automotive, water, and aviation industries to the military [3,4]. Due to their widespread use and different manufacturing methods, not all batteries should be used for the same purpose. They act as an energy store in all cases, but there are different temperature and performance requirements in entertainment or industrial devices, and others still in automotive applications. Batteries used when in traffic must also comply with special safety conditions; therefore, many aspects need to be considered when designing the system [5–7]. Furthermore, during their use, various risk analyses are performed on them [8,9]. The use of batteries in the military has long been of interest, with several publications addressing the topic [10,11]. Due to recent changes in requirements, battery diagnostic and testing procedures have lately undergone significant development [12,13]. Several old and new diagnostic proce- dures can be observed in the literature for both system disassembly and non-disassembly methods. The most accurate condition estimates are obtained by disassembly tests, which examine the structure of the battery. Such procedures include CT [14,15], ultrasonic [16], or surface digitization (DIC) [17–19] methods. The disadvantage of these solutions is that they require the disassembly of the battery system, which is a slow and complicated procedure. It may also void the warranty of the vehicle. Therefore, in the case of non-self-developed Energies 2022, 15, 4791. https://doi.org/10.3390/en15134791 https://www.mdpi.com/journal/energies