In the modern world, the rapid advancement of new technologies is accompanied by an increasing energetic demand. Following today`s trend, energy consumption will undoubtedly increase in the following years. Over the last 50 years, lithium-metal batteries have been considered as potential candidates for long-term high-performance electrochemical storage. (1) Although their operation is effective, they still present limitations mainly due to lithium dendrite growth associated with electrodeposited Li+ from the electrolyte on the anode material. This phenomenon causes internal short-circuits resulting in premature battery failure. (2) Various solid-state battery systems are being developed in hope to resolve the said issue. Amongst others, solid polymer electrolytes (SPE) have been investigated since Armand`s work in the 80`. (3) Even though these systems have non-flammable properties and successfully suppress dendrite growth, most SPEs do not reach ionic conductivities values higher than 10-3 S/cm at room temperature and offer lower energy densities and cycle number compared to the standard liquid electrolyte counterpart. (4) As a result of that, an increasing number of published literature shows off new engaging SPE systems. However, oftentimes, the presented performances are hardly reproducible due to the lack of precise and detailed experimental conditions. It is believed that some overlooked factors during processing may affect the aforementioned performances. (5-7) Certain parameters that affect ionic conductivities of SPEs have been investigated by techniques including but not limited to electrochemical impedance spectroscopy (EIS) and solid-state 7Li-NMR. It will be demonstrated that these parameters must be precisely controlled to ensure the reproducibility and the validity of measurements. Finally, it will be shown that this study can be applied to several types of polymers.1: Hall P. J., Bain E. J., Energy Policy, 36, 4352 (2008).2: Lisbona D., Snee T., Process. Saf. Environ., 89, 434 (2011). 3: Armand M. B., Ann. Rev. Mater. Sci. 16, 245 (1986).4: Penghui Y., Haobin Y., Zhiyu D., Yanchen L., Juan L., Marino L., Junwei W., Xingjun L., Front. Chem., 7, 522 (2019).5: Fullerton-Shirey S. K., Maranas J.K, Macromolecules, 42, 2142 (2009).6: Devaux D., Bouchet R., Glé D., Denoyel R., Solid State Ion., 227, 119 (2012).7: Wang X., Zhang L., Li G., Zhang G., Shao Z.G., Yi B., Electrochim. Acta, 158, 253 (2015)