This paper introduces a simplified active battery balancing technique using a CLLC resonant converter functioning as a fixed-ratio DC transformer. Operating at its resonant frequency, the system enables automatic, bidirectional energy transfer between cells based on voltage differences, without complex control, sensing, or frequency modulation. This approach enhances efficiency, supports both cell-to-cell and module-level balancing, and is suitable for batteries, supercapacitors, and hybrid systems. Simulations using LT-Spice confirm the method’s effectiveness in equalizing voltages. A hardware prototype validated these results, demonstrating real-world feasibility and autonomous balancing performance. The design is a promising solution for energy storage in electric vehicles and grid applications. Future work aims to expand multiport capability and explore detailed power distribution analysis.
