dc/dc charger

HI CREW, got problems after fitting a dc/dc 20amp charger, I have got 240watts of panels up on canopy in front of roof top tent, the sun this time of year in north qld is more than enough, the panels charge 2 marine batteries, & run 2/40lt engels ,with one on freeze. I went away last year for 3 months to cape York with no use of generator or electricity. this year I put in a dc/dc 20amp charger and had trouble while camped up with solar only, its seems I was not getting enough power through it, I by passed it & hooray im back to normal with no more running of generator. the charger is very simple to wire in, & thought the thing would be great ? the panels have the usual regulator on the back. I havnt named the charger , because I don't know if im aloud to ? cheers