I call converters that utterly fail to recharge a battery boondocking a "Zsa Zsa Gabor Backpacker". Some converters are better than others. But an hour at max output is sort of ridiculous for a top 20% charger. That would be 36 amp hours and still nowhere near full charge. If the power and cables check good. Yank the scrap and hurl it at a howling dog. Putting in a divider switch to halve 12 volts could allow a second power supply to be used. The switch would be in the positive circuit. Nothing wrong about doing that as it would not be a series tap. Think about that. Apples & Hand Grenades.
Many hours working with Cheapos Meanwells & Megawatts have convinced me the toroid chokes are overwhelmingly the majority heat producers. Capacitors, bi polar transistors and Schottky rectifiers absorb radiated and convected heat. I am ready to do a roof reinforce and mount a serious 120mm fan with appropriate grilles. External. Right atop the chokes. And the circuit board versus case openings is a real Larry, Curly, and Moe design. What has happened to intelligent thermodynamics designing? One single 1/2" vent hole adjacent to those neighboring chpkes would improve cooling dramatically. The entire starboard side has nothing on it. Oh by the way, this isn't theory - dumping from 113 F internal to 91 F ain't chicken feed. The 120 mm fan is a plan the hole is a reality.
