Dry camping batteries charging

So I'm going to install a 7 pin outlet on the fifth wheel and charge my four deka batteries from the trucks second plug in at the bumper. I have been told it will only put out 2 amps or 14.6 volts , but while traveling that's better than running the lp Onan . I a hoping for a significant improvement in this department.

Carl & Christine, 2012 Landmark Rushmore, 2005 Silverado crew cab lt 8 foot bed 6.6 lly /Allison -custom dual exhaust-198000 miles !