The 21st edition of the annual international “Symposium on Modeling and Experimental Validation of Electrochemical Energy Technologies” (ModVal) took place in Karlsruhe this year and was organized by Offenburg University of Applied Sciences and the Karlsruhe Institute of Technology. The event focuses on the modeling, simulation and experimental validation of rechargeable batteries, fuel cells and electrolysers. This year's program reflected the thematic diversity and research dynamics of the field: two plenary lectures, four keynotes, 36 technical presentations in two parallel sessions and more than 100 scientific posters - a new record - offered participants working in electrochemical energy technology comprehensive insights into current developments and future trends. With lively discussions, inspiring presentations and a wide range of exchanges, ModVal 2025 was a great success and an important contribution to research on sustainable energy technologies.