High-power electric vehicle (EV) charging can create power peaks that exceed available distribution-grid capacity. This paper investigates retired Leclanché GL60 G/NMC cells from the 4.3 MWh Ellen e-ferry battery system as stationary buffers for grid- constrained DC fast-charging sites. A one-minute time-domain simulation combines a 500 kW grid connection, 300 kW double charging stations, stochastic daily demand, a Danish time-of-day arrival pattern derived from Campus Bornholm measurements, and a battery model with SOC, C-rate, efficiency, grid-recharging, and capacity-fade constraints. Sites with one to six stations and 6, 9, 12, or 20 sessions per day per station are evaluated. The minimum buffer is identified in 25 kWh increments subject to less than 0.5% annual unmet energy. Degradation is estimated using equivalent full cycles, manufacturer cycle-life data, and calendar-aging sensitivity. Required capacity ranges from zero to 1.025 MWh. For six stations at 20 sessions per day per station, the minimum buffer experiences approximately 236 EFC per year and reaches 70% SOH after approximately 7.2 years under the