This paper presents a non-invasive technical analysis of the degra-dation of four lithium-ion batteries (LIBs) used in extreme frigid weather. In contrast to other studies in which the batteries were tested in laboratory conditions, the LIBs studied in this paper were aged in a real application, more specifically in the WindSled project. In this project, an expedition was made using a zero-emission vehicle drawn by kites, covering more than 2500 kilometers on the East Antarctic Plateau. The study performed in this paper aims to quantify the degradation of the LIBs during the expedition. The results show a 5 % capacity fade, a 30 % increase in the internal resistance and no substantial increase in the impedance of the solid electrolyte interface (SEI). Moreover, no evidence of dendrite growth at the anode is inferred by the interpretation of the distri-bution of relaxation times (DRT), incremental capacity analysis (ICA) and differential voltage analysis (DV). Based on these re-sults, it can be claimed that the LIBs used in the WindSled Project can successfully operate under 50 C. Furthermore, since non-invasive techniques were used to characterize the batteries, they can still be used in upcoming expeditions, with subsequent financial and environmental benefits. This work was supported in part by the Spanish State Research Agency (AEI) under Grant PID2019-111262RB-I00/AEI/10.13039/501100011033, in part by the European Union under the H2020 Project STARDUST under Grant 774094, and in part by the Public University of Navarre through the research project ReBMS PJUPNA1904 and a Ph.D. Scholarship.