High-power electric vehicle (EV) charging infrastructure is increasingly constrained by limited grid connection capacity, particularly in locations where reinforcement is costly or infeasible. Battery-buffered fast-charging stations based on second-life lithium-ion batteries offer a promising solution by decoupling charging power from grid availability while extending the useful lifetime of retired batteries. This paper investigates the technical feasibility and lifetime implications of deploying retired e-ferry battery cells as stationary buffer storage for grid-constrained DC fast-charging hubs. A time-domain simulation framework is developed that combines physics-informed EV charging profiles, stochastic arrival processes, grid power limitations, and a battery energy storage system (BESS) with C-rate constraints, SOC-aware derating, and grid recharging between sessions. A throughput-based state-of-health (SOH) degradation model calibrated from an estimated cycle-life range is integrated, and capacity fade is coupled directly to available pack energy. The framework is applied to a 4.3 MWh battery system assembled from retired maritime battery cells and evaluated for double fast-charging stations rated at 300~kW (2 x 150 kW) under a 500 kW grid connection. Results demonstrate that a properly controlled second-life BESS can support multiple high-power charging stations with minimal unmet energy while maintaining operation within defined SOC and C-rate limits. Furthermore, the simulated annual throughput leads to modest SOH degradation, indicating that second-life maritime batteries can provide substantial additional service life in buffer applications. The presented methodology enables systematic sizing and lifetime assessment of second-life battery-buffered fast-charging stations and supports informed design decisions for grid-constrained e-mobility infrastructure.