Lithium-ion batteries are getting larger due to the expansion of transportation and mass storage markets and they can now contain up to thousands of cells. However, a sole damaged cell can significantly impact the whole battery pack efficiency. Thus, the diagnosis of a single cell remains critical for those systems. Many methods exist in which the cell is considered homogeneous. We recently developed a heterogeneous equivalent circuit model that considers an internal resistance distribution to better represent a real single cell behaviour. This internal resistance distribution (IRD) may bring valuable information about a single cell internal quality, but only if it is determined with a sufficient accuracy. In this paper, we propose an algorithm that allows a responsive determination of the IRD. The results are compared to previous determination methods. This IRD, which is determined thanks to the preliminary construction of a homogenous model and a single discharge, is also valid for other operating conditions. The determination of a cell IRD can be used as a non-invasive diagnosis tool to track the internal degradations of a cell. The IRD of two different cell, one aged and one new are then compared, the IRD of the aged one being on average larger. This proves the relevance of the determination method and its use to get an insight into a cell. Differences in shape between the aged and the new cell IRD are discussed, as well as criteria that seems interesting. Although this work is developed for a single cell, its initial goal is to be used to detect a damaged cell inside a battery pack and may thus be applied to several cells connected in parallel.