To get a better understanding of the air circulation in the charger, here some pictures of my charger. I took it apart out of curiosity.
That’s how it looks from the outside when you remove it.
orange cable in front: connection to blue mains plug
connection next to it: snorkel (The charger is caspuled and can “breath” through that snorkel)
black cable at left rear: connection to 12-V-battery
orange cable at rear: connection to main battery
Behind a cover is the outer fan, that blows air through cooling fins. The rest of the charger is capsuled.