Abstract
Battery-electric and hybrid ships combine battery energy storage systems with networked control, machine-learning state estimation, digital twins, high-capacity charging, and, in some applications, second-life cells. These configurations introduce risks for which maritime approval instruments may lack verifiable acceptance criteria. This paper defines a Regulatory Readiness Level (RRL) from 0 (unrecognised) to 4 (verifiable acceptance) and applies it to nine frontier risks in three families: cyber-physical, AI-driven, and second life/lifecycle. The assessment covers IMO, EMSA, IACS, IEC, UL, NFPA, and battery requirements of five classification societies, using instruments in force on 31 July 2026. No risk reaches RRL 4 under the study’s target. Median readiness is RRL 2: one risk is at RRL 0, two at RRL 1, four at RRL 2, and two at RRL 3. The two RRL 3 cases illustrate different limitations: state-of-health estimation is verified periodically without qualification between tests, whereas mixed-chemistry and mixed-state-of-health packs are addressed through prohibition rather than qualification. Baseline priority places AI3, auditability of AI safety functions, first, with AI2 and SL1 in the next band; SL1 is sensitive to aggregation. Ordinal dominance excludes CP2, CP3, and SL1 from the lead without assuming equal spacing. Sensitivity analysis shows that uncertainty in readiness classification has a larger effect on ranking than uncertainty in severity and exposure. Adjacent-sector assurance mechanisms provide templates for maritime incorporation, and the paper proposes an acceptance objective, verification method, and regulatory vehicle for each risk.