Introduction For mid- to long-distance FPV drone flights, the primary concern is preventing an unexpected battery drop-out. In addition to reliability, optimizing battery selection is crucial for maximizing flight range while balancing weight and performance. Calculating the optimal capacity The maximum distance a drone can travel can be estimated using the formula: $$\mathrm{distance} = k_{drone} \cdot \frac{\eta \cdot Q}{m_e + \rho \cdot Q}$$ where: $\mathrm{distance}$: Maximum travel distance in kilometers (km). $k_{drone}$ (Drone Constant): An empirically determined constant reflecting the drone’s aerodynamics and efficiency. $Q$ (Battery Capacity): Battery capacity in amp-hours (Ah). $\eta$ (Usable Battery Factor): The fraction of the battery’s capacity that can be safely utilized. For example, $\eta = 0.95$ for Li-ion batteries and $\eta = 0.8$ for LiPo batteries. $m_e$ (Empty Mass): The drone’s mass without the battery (including payloads like a camera), in kilograms. $\rho$ (Battery Mass per Ah): The battery’s weight per amp-hour, which reflects its energy density. For example, $\rho = 1$ for Li-ion and $\rho = 1.4$ for LiPo batteries. This formula allows you to predict the impact of different battery capacities on your drone’s flight range once you have determined its drone constant, $k_{drone}$. ...