The subject of this article was a comprehensive analysis of battery behavior in UAVs in terms of its key parameters (current, voltage, SOC, depth of discharge, etc.), including temperature and the “heat of temperature” value generated in the cells. The main objective of the work was to identify key phenomena occurring during intensive phases of operation of the tested lithium-ion battery (e.g., start-up, maneuvers), including, among others, a rapid increase in current consumption associated with a rapid drop in voltage and a significant decrease in SOC, as well as a simultaneous increase in temperature and “heat” values. Furthermore, in their research, the authors paid particular attention to the fact that during steady-state or reduced load phases, key parameters (current, voltage, SOC) stabilize, while in the next cycle of intensive battery operation, similar thermal spikes occur again. The analysis showed that cyclic loads and thermal shocks affect battery life and capacity, which translates into operational safety. In this context, the article points to the need to use advanced BMS, temperature monitoring, depth of discharge limitation, and cell cooling integration to extend the life of the UAV power system. In the final part of the paper, based on the conducted research (analysis, models, controllers), as well as the UAV simulation tests carried out in the MATLAB/Simulink environment and the results obtained, final practical conclusions were formulated.