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This paper describes the design of a modular battery management system for electric off-road vehicles, where lithiumion batteries are expected to be widely used. A massive electrification of off-road vehicles can be enabled by the availability of a standard battery module, provided with an effective management unit. The design and some preliminary experimental results of the module management unit are discussed in this paper. The unit contains a high current active equalizer that enables the dynamic charge equalization among cells and maximizes the usable capacity of the battery. Keywords-Battery Management System, Active balancing, Electric Off-Road Vehicles, Lithium-ion battery technologyI.

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The study, made by ENEA in cooperation with the University of Pisa as part of the activities supported by the Italian Ministry of Economic Development in the framework of the Program Agreement for the Research on the Electric System, is related to the situation of Italian market and demonstrates the feasibility of the electrification for off-road vehicles and the possibility to realize it by the means of standard modules.The preliminary dimensioning of the standard modules is also reported, defining the main electric characteristics (voltage and capacity) and the type of chemistry: LiFePO 4 is proved to be a very effective solution for this kind of application. The activity goes on towards the final design and the realization of demonstrator units.

In this paper, starting from the results of the campaign of laboratory tests, a probabilistic method for describing the distributions of battery lifetime is presented. The approach is based upon numerical solution of the Rakhmatov and Virudhula battery model. In the final part of the paper, numerical tests show that the battery expected lifetime can be well described by models, such as the Inverse Weibull or the Lognormal, with decreasing hazard rate for large mission times, a fact which has been sometimes observed in literature as a paradox. Some considerations with respect to parameter estimation of the reliability models close the paper