Battery Retirement for Electric Flight Based on Mission Voltage Capability

Battery retirement in electric flight is commonly determined from fixed state-of-health thresholds, although these thresholds do not directly represent the voltage capability required to complete a mission. This paper investigates how battery health states should be translated into mission-referenced retirement decisions using complementary evidence from laboratory-collected UAV battery-aging data and 197 real maneuver flights, 22 eVTOL cells with measured landing-window voltage, and a separate 24S1P LiPo-module cycling dataset. We first show that the relationship between capacity retention and mission capability is reference dependent: the leave-one-cell-out capacity state associated with the measured eVTOL voltage reference shifts from a median of 0.831 at 2.7 V to 0.916 at 3.0 V, such that the same fixed capacity rule can retire a battery either before or after the corresponding mission-voltage reference. Simply adding an independent resistance threshold does not resolve this mismatch, with 75 of 76 evaluable fixed-grid selections reproducing the capacity-only trigger. We therefore translate health state into mission capability through a current-conditioned voltage replay that combines strictly prior capacity, a depth-dependent C/5 loaded-voltage curve, pulse resistance, and premission voltage initialization. Across 18,864 missions from 21 cells, the replay reconstructs the measured landing-window minimum with a median residual of −0.015 V and an RMSE of 0.096 V. Its retirement trigger is substantially closer to the measured reference than fixed capacity rules at the registered 2.7- and 3.0-V rows. The in-house UAV analysis shows, however, that this health-to-mission translation does not automatically transfer across battery types and high-load operating regimes, while the LiPo-module trajectory provides a complementary module-level illustration of reference-dependent retirement timing. Finally, retirement timing is shown to alter pack-equivalent replacement intensity and replacement-associated burden. These results indicate that battery retirement for electric flight should be conditioned on the mission-voltage capability to be preserved rather than interpreted through a universal health threshold.