Non-intrusive diagnosis and prognosis methods are increasingly adopted to track Li-ion batteries ageing without additional cost due to destructive processes for post-mortem analyses. To qualify and quantify internal degradation mechanisms of a cell, Incremental Capacity Analysis (ICA) and Differential Voltage Analysis (DVA) have proven themselves to provide precise outputs on the battery state of health. These differential methods require close-to-equilibrium Open Circuit Voltage (cte-OCV) measurements to decipher ageing paths depending on the utilization.This poster presents an ageing campaign preliminary study on some Graphite//LiMn1-xFexPO4 and Li4Ti5O12/Ni1-x-yMnxCoyO2 based cells. It focuses on the reference performance tests chosen to be the most complete on both cell and electrode levels. As the battery cte-OCV measurement is a lengthy process of at least 25h, the reference tests should be well-defined to acquire as many data as possible in a single shot. A comparison is carried between constant current measurements and incremental charges with relaxation (GITT) to approach thermodynamic equilibrium, as well as the conditions and sampling rates to leverage differential method curves without further smoothing.