Experimental Assessments of Second-Hand Battery Degradation under V2G Operation for Electric Vessels

Vessel-to-Grid (V2G) technology offers
significant potential for supporting grid stability, boosting
renewable energy integration, and increasing the profitability
of electric vessels (EVs) through intelligent energy
management. However, concerns linger regarding the impact
of frequent charge-discharge cycles on battery health,
especially with the further inclusion of the V2G power cycles.
The impact of this approach has been well-studied for roadbased
electric vehicles, where the concluded outcomes are
particularly customised based on the road vehicle operational
duty cycles. However, this approach remains largely
unexplored for marine EV batteries, due to their unique duty
cycles and implementation of second-hand battery systems
for use in V2G technologies. This paper addresses that gap
by investigating the impact of V2G on commercial lithiumion
battery packs (6.8 kWh, 44V, 12 cells) used in smallpower
leisure and light-duty marine vessels. A dedicated
testbed was developed, incorporating a bidirectional DC
power supply and integrated battery management system.
Simulated operational cycles were applied to assess V2G use
cases such as peak shaving, renewable energy integration,
and energy trading. Accelerated cycling tests replicated realworld
V2G patterns over several weeks, allowing for
continuous monitoring of the battery state of health (SOH).
Results show that while V2G is technically viable and
economically beneficial for marine EVs, its effects on battery
SOH, especially for second-life batteries, must be carefully
managed to ensure long-term sustainability.