An experimental investigation is presented to validate endurance estimates for a battery powered flight vehicle. In this study a radio controlled model aircraft was ‘flown’ inside a wind tunnel. Various Lithium Ion batteries were used to power the model. Battery electrical characteristics were recorded during each run to assess battery discharge behaviour. Theoretical estimates based upon battery characteristics yielded endurance estimates within 3% of that measured experimentally. The discharge characteristics of the batteries were found to be the largest source of uncertainty for endurance estimates.