you may just try an external 3 step charger and see if that solves the problem, and think about another converter. The Progressive Industries units are recommended by many and you can replace just the converter section of your existing unit, even if it is part of the main box by changing the wiring slightly.
In my C-cross the Converter is separate and behind the main box so it is easy to do, but in some units the converters are integral to the distribution panel. Either way it can be done fairly easily.
In the meantime you can use an external charger to keep the battery charged up.
2007 Chevy 2500HD Classic LBZ Duramax/Allison (Stock)
2005 Bigfoot 1500C8.2 AWESOME