FISITA World Congress 2023 – Abstract Self Reconfigurable Battery for automotive application: simulation and testing Nicolas Léto1*, Sylvain Bacquet2*, Rémy Thomas2, Yan Lopez2, Jérôme Lachaize1, Paul Boucharel1, Lionel Guichard1, Leandro Cassarino2 1 Vitesco Technologies, 40, Avenue du Général de Croutte, 31100 Toulouse – France 2 Commissariat à l'énergie atomique et aux énergies alternatives, 17 rues des martyrs, 38054 Grenoble - France KEYWORDS – Battery Electrical Vehicle, Self Reconfigurable Battery, lifetime extension, energy optimization, optimized battery management system ABSTRACT - Research and/or Engineering Questions/Objective A Self Reconfigurable Battery (SRB) allows to individually control each cell of the pack to carry out a dynamic balancing whatever the phases of use of the vehicle. Other features such as control of the DC Link voltage, improved AC and fast DC charging are also feasible. This article presents the design and production work carried out jointly by Vitesco Technologies and the CEA to build a demonstrator representative of an electric vehicle pack. The idea is to compare by simulation and testing, a SRB to a conventional battery pack (CBP) to highlights the benefits and weaknesses of both solutions. - Methodology Different configurations of batteries in a representative electrical vehicle environment have been simulated. The comparison is relevant at an energetic point of view only. Comparatively to a CBP for a given segment, the equivalent SRB to be considered has more cells in series and smaller cells. The two batteries have been dimensioned to provide the same energy at the wheel at the beginning of life, considering internal resistance and capacity including representative energetic cells with their actual parameters and representative cell dispersion within the pack. To correlate this comparison, tests have been conducted on two configurations (one for CBP, the other for SRB) using the same battery pack for a discharge imposed by several WLTC driving cycles and for a fast DC charge. - Results By simulation, an aged SRB has been compared to the aged CBP with a capacity of 70% and a capacity uniform distribution of ±4.8% with accurate losses repartition. Thanks to the Control DC link Voltage capability, a better global powertrain efficiency is achieved resulting in an autonomy increased by 6% (+24km) with WLTC driving profiles and a DC charge from 20% to 80% of SOC faster by 20% (30 minutes vs 42). Tests conducted on the demonstrator to correlate these gains showed similar results on WLTC driving cycles (SRB saves 6% more energy than CBP) and on the charging time, faster by 22%. - Limitations of this study Some assumptions on the simulation have been made regarding the losses and thermal behavior. The tests conducted on this demonstrator on test bench provided useful results regarding expected performances of this technology. However, the representativity of this demonstrator is partial since it is not a fully integrated battery for electrical vehicle mechanical and electrical design. - What does the paper offer that is new in the field including in comparison to other work by the authors? Other simulations have been conducted on several driving and charging cycles in different conditions with a more representative pack model regarding thermal and losses aspects, thanks to new hypothesis from a new design to cost conception. - Conclusions: This paper presents the experimental results of the advanced functions that a SRB allows (Control DC Link voltage ; power balancing in operation ; Charge on AC network without inverter ; Fast DC charge). The comparison by simulations correlated by tests with a conventional battery pack highlights performance improvements in terms of efficiency in driving as well as in terms of fast charging rate. The results obtained also show, from the battery life extension, the capability of the SRB to correctly operate heterogenous cells reproducing the ageing observed on real automotive battery packs.

Mr. Nicolas LETO, Innovation project manager, Vitesco Technologies