An in-situ thermal characterization theoretical model and method specifically designed for this battery type was proposed aiming at the characterization of heat-generating behaviors in aluminum-air fuel cells for automotive power applications. The influence mechanisms of operating temperature, electrolyte concentration, and current density on the battery's temperature rise during discharge, heat loss, heat generation rate, and discharge efficiency were analyzed. Results show that the aluminum-air battery's temperature-rise amplitude, heat loss, and heat generation rate increase with decreasing operating temperature and increasing electrolyte concentration. The battery’s heat generation rate gradually decreases over the discharge duration, while the discharge efficiency improves with increasing operating temperature and current density. Electrolyte concentration significantly impacts the battery’s discharge efficiency. The operational efficiency approaches 78% at a concentration of 3.0 mol/L. Efficiencies fall below 60% at concentrations of both 1.0 mol/L and 6.0 mol/L, indicating that excessively high or low concentrations detrimentally affect discharge efficiency.