This paper presents a comparative study on lithium-polymer battery performance and degradation at a discharge rate 20C during UAVs missions with FPV computer vision cameras with two discharged experiments. The first experiment was the initial usage up to cycle 6, and the baseline showed performance with minimal capacity loss, an average bending angle of 6°, and temperatures average 50 ℃. The second experiment, which focused on extended usage until battery swelling, revealed significant degradation. In this phase, amp-hour counting dropped to 86.98%, bending angles increased to 25°, and hotspots reached a temperature of 74 ℃. The study demonstrated that performance decline accelerated beyond cycle 10, with cycle 12 marking a critical failure point, preventing reuse. The advantage of flexible bending sensors was that they could detect swelling earlier than temperature methods. However, there are limitations to individual metrics. These findings emphasize the importance of integrating multi-parameter diagnostics to ensure UAVs battery reliability. Future work aims to explore real mission profiles and develop advanced monitoring tools and predictive algorithms for enhanced safety.