Second life batteries are a promising option for increasing the economic value of photovoltaic generation while supporting more sustainable battery use. This work revisits the economic operation of a 4.3 MWh second life battery, motivated by the Danish E-Ferry Ellen case, coupled to a 2.1 MW Danish PV plant using measured plant generation data and a deterministic mixed integer linear programming framework. The baseline model follows our earlier case study, which used hourly PV data from May 2014 to April 2015 and compared direct PV sale, second life battery operation, and equivalent new battery alternatives under Danish electricity prices.

The main extension of this paper is twofold. First, the market assessment is updated using recent Danish electricity EL Spot prices for the period May 2024 to May 2025. Second, the optimization is extended with degradation aware economics using a battery wear cost derived from equivalent full cycles, enabling a more realistic comparison between second life and new battery systems. The study preserves the original operational setting, including PV only charging, hourly scheduling, and comparison against a new battery with varying capacity ratio, while adding a focused sensitivity analysis on second life battery state of health and round trip efficiency.

The results quantify how current Danish market conditions affect the revenue potential of second life battery operation and show how degradation cost changes the economic ranking between second life and new battery options. In particular, the analysis identifies the profitability change relative to the 2022 price case and determines whether the second life battery remains economically attractive once battery wear is included. Sensitivity results further show how the outcome depends on residual battery condition and efficiency assumptions.

The work is based on measured field data combined with original optimization based analysis. It is relevant for renewable integration, battery reuse, and market based scheduling of storage systems. The findings provide an updated and more decision relevant assessment of second life battery use for Danish PV plants under current electricity prices.