If the size of hte battery bank is not what you are questioning is it by chance to voltage? Check all cable connections to be sure they are clean and tight at battery, frame (for ground), converter and any circuit breakers inbetween.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7