Performance and aging diagnostic on lithium iron phosphate batteries for electric vehicles and vehicle-to-grid strategies : from the cell to the system level

Marongiu, Andrea; Sauer, Dirk Uwe (Thesis advisor); Damiano, Alfonso (Thesis advisor)

Aachen : Institut für Stromrichtertechnik und Elektrische Antriebe (ISEA) (2017, 2018)
Book, Dissertation / PhD Thesis, Report

In: Aachener Beiträge des ISEA 100
Page(s)/Article-Nr.: 1 Online-Ressource (ix, 222 Seiten) : IllustrationenReport number: ISEA RWTH-100

Dissertation, RWTH Aachen University, 2017


In this work all aspects of a lithium iron phosphate battery are explored, going from its working principle until its correct use and integration in the electric system. The work investigates firstly the battery’s electric performance and its changing during aging, demonstrating that the characteristics of the plateaus present in the open circuit voltage curve change differently based on the battery degradation. According to these findings, a novel on-board algorithm approach for the estimation of the actual battery capacity is introduced. Through the determination of the single degradation modes, the actual battery’s state of health can be assessed with an error within 2%. The proposed algorithm is part of a newly developed Battery Management System (BMS) concept designed for vehicle-to-grid (V2G) operation. Thus, a simulation tool is presented, with the aim of analyzing the behavior of the vehicle battery packs of a car fleet when additional cycle operations due to grid services are requested. The results of the simulations demonstrate that the adoption of adequate strategies allows a more uniform aging of the entire fleet, with an increase of the average battery lifetime of approx. one year.