The battery passport is proposed as a method to make the use and remaining value of batteries more transparent. The future EU Battery Directive requests this passport to contain the round-trip energy efficiency and its fade. In this paper, an algorithm is presented and demonstrated that estimates the round-trip energy efficiency of a battery pack. The algorithm identifies round trips based on battery current and SoC and characterizes these round trips based on certain conditions. 2D efficiency maps are created as a function of the conditions `temperature' and `RMS C-rate'. The maps are parameterized using multiple linear regression, which allows comparison of the efficiency under the same conditions. Analyzing data from three battery-electric buses over a period of 3.5 years reveals an efficiency fade of up to 0.86 percent point.
@article{arxiv.2308.15828,
title = {Round-Trip Energy Efficiency and Energy-Efficiency Fade Estimation for Battery Passport},
author = {Camiel Beckers and Erik Hoedemaekers and Arda Dagkilic and Henk Jan Bergveld},
journal= {arXiv preprint arXiv:2308.15828},
year = {2024}
}