This presentation will focus on the conversion of the passenger vessel FGS Sissi from conventional propulsion to fully electric operation using Lehmann Marine’s LFP battery systems. The session will address the practical challenges of integrating batteries into an existing vessel not originally designed for electrification, including space and structural limitations. Using this real-life retrofit project as an example, the presentation highlights the importance of system support beyond hardware supply, from dimensioning and layout to FAT, commissioning, and service support.