Driven　by　growing　environmental　awareness　and　supportive　regulatory　frameworks,　electric　vehicles　(EVs)　are　witnessing　accelerating　market　penetration.　However,　a　key　consumer　concern　remains:　the　economic　impact　of　battery　degradation,　manifesting　as　vehicle　depreciation　and　diminished　driving　range.　To　alleviate　this　concern,　EV　manufacturers　commonly　offer　performance-guaranteed　free-replacement　warranties,　under　which　batteries　are　replaced　at　no　cost　if　capacity　falls　below　a　specified　threshold　within　the　warranty　period.　This　paper　develops　a　symmetry-informed　analytical　framework　to　forecast　time-varying　aggregate　warranty　replacement　demand　(AWRD)　and　to　design　optimal　battery　inventory　strategies.　By　coupling　stochastic　EV　sales　dynamics　with　battery　performance　degradation　thresholds,　we　construct　a　demand　forecasting　model　that　presents　structural　symmetry　over　time.　Based　on　this,　two　inventory　optimization　models　are　proposed:　the　Service-Level　Symmetry　Model　(SLSM),　which　prioritizes　reliability　and　customer　satisfaction,　and　the　Cost-Efficiency　Symmetry　Model　(CESM),　which　focuses　on　economic　balance　and　inventory　cost　minimization.　Comparative　analysis　demonstrates　that　CESM　achieves　superior　cost　performance,　reducing　total　cost　by　20.3%　while　maintaining　operational　stability.　Moreover,　incorporating　CESM-derived　strategies　into　SLSM　yields　a　hybrid　solution　that　preserves　service-level　guarantees　and　achieves　a　3.9%　cost　reduction.　Finally,　the　applicability　and　robustness　of　the　AWRD　forecasting　framework　and　both　symmetry-based　inventory　models　are　validated　using　real-world　numerical　data　and　Monte　Carlo　simulations.　This　research　offers　a　structured　and　symmetrical　perspective　on　EV　battery　warranty　management　and　inventory　control,　aligning　with　the　core　principles　of　symmetry　in　complex　system　optimization.