Lithium-ion batteries play a crucial role in new electronic applications due to their high energy density, size, safety and efficiency, and they are considered a critical aspect of modern life. However, the increasing prevalence of fast-charging technology has raised user concerns about its impact on the immediate, daily performance of smartphone batteries. This paper investigates the hypothesis that fast charging diminishes a battery's duration throughout a single usage cycle compared to standard charging methods. We propose a comparative study analyzing the daily battery performance of modern smartphones under various charging regimens, including fast, normal, OEM (and third-party chargers). The methodology involves developing an experimental setup of three distinct electronics devices (a tablet, a laptop and a smartphone) to continuously measure parameters like voltage, current, temperature and state of charge, under different charging conditions to assess their direct effect on single-cycle discharge duration. Findings demonstrate that fast charging generates significantly more heat—a known factor in long-term degradation—and even with sophisticated thermal management they tend to last shorter through the day with increased cell aging. This research highlights the distinction between long-term battery health and immediate daily performance, aiming to clarify consumer misconceptions and underscore the importance of certified charging hardware.