Using the "on board" converter it can take several days (up to a week) to fully charge a 2 battery bank. That is because as the battery recharges, the charging current is reduced to a trickle (less than 1/2 amp) to avoid overcharging and boiling your battery dry (multiple charging stages).
You can watch the process with a battery monitor like the TM-2025RV system. Initially the battery can take about 26 amps and by the end of the first hour it is at 9 amps. By the end of the day it is about 1 amp. It will stay about an amp or less for several days as it goes into trickle mode.
Lou, Laura, & Freya the wonder dog
2008 GMC Sierra 3000HD Crewcab SB Allison Duramax
2019 Flagstaff 8529FLS - Pullrite 3300
HAM CALLSIGN - KC3FFW