BMW 2025 EWS CAS Keys Rechargeable Battery

This is a replacement rechargeable battery for BMW EWS and CAS key modules, used to maintain the internal memory-retention circuit that keeps the transponder synced to the vehicle's immobilizer. A weak or depleted cell in these modules is a common cause of intermittent no-start or key-not-recognized faults; replacing it restores normal EWS/CAS function without requiring a full key module replacement. This part is specific to BMW EWS/CAS key housings - confirm the exact module variant before ordering, as EWS and CAS generations use different housings.