An afterthought, but you should study up on lead-acid batteries and their properties. Not familiar with your rig, but your batteries should get 14+ volts with your rig engine running (not the generator).
If after pumping charge with at least 14 volts for a half hour - and you don't see any appreciable increase in battery voltage - you may have some dead cells in one or more of the batteries.
I would suggest at minimum investing in a small rooftop 100 watt solar panel setup. Unless you're stored indoors, that will keep the batteries topped off above 13 volts.
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