Easily swapping input/output of dc2dc charger

[LifesBetterWhenYoureBeating]

I have a dc2dc charger that is normally used to charge my lifepo4 house battery from the starter, but sometimes I go for long periods without running the engine and may want to top up the starter, so I'm looking for an easy way to swap the input/output of the dc2dc charger. Is there some sort of switch that would take a couple inputs and connect them either directly or criss crossed to two outputs? Or any other way I could achieve the same

Thanks in advance

[Munoz]

Depends on whether your DC-DC charger has a common ground or isolated ground, if it's common ground you can use a DPDT switch, if it's isolated ground you will need a quad-pole, double throw switch as you need to reverse the negative wires as well...

[LifesBetterWhenYoureBeating]

Mine has a common ground so it looks like a dpdt would work, but so far I've only found them for up to 30A, which is my dc2dc's max current. I don't think it'd be a good idea to run 30A through those tiny things for an hour or more...

[Munoz]

Yes, they can be a bit harder to find for high current applications.
One option would be a "rotary change over switch," designed for generators and other electrical gear