Electrical energy sources and batteries are currently in great demand. The demand is growing, and their use is on the rise in a variety of applications. In contrast, there are limited both production/manufacturing options and an effort to ensure more environmentally friendly acquisition, operation and use. In this article, we study, test, and model the charging process of Li-ION batteries. We study a set of long-term stored Li-ION batteries and compare the data and results with a set of new Li-ION batteries. The charging data are obtained experimentally by long-term testing, and the volume (of the data) is very large and statistically very representative. Modelling of the Li-ION battery charging process is based on specific growth model forms. Furthermore, the charging process is simulated using special forms of the diffusion process, specifically the Geometric Ornstein-Uhlenbeck process, which seems to be the most suitable for this purpose. The research is carried out with the aim to obtain the first passage time (FPT), i.e. the charge time of the battery. The first passage time is further studied with respect to the suitability of its expression using parametric probability distributions. We also acquired the numerical statistics of the charging time FPT as well as the respective parametric distribution. The FPT results obtained for long-term stored and new Li-ION batteries were compared using well-known and lesser-known statistical tests, such as the Kullback-Leibler divergence.