If you have room a second battery it is a really a good idea.
If you are using the refer in 12v (on the road), as soon as the engine is turned off so should the ref. just a huge draw on battery. Even refueling I would 1st turn it off. Should also turn off refer at least an hour before you arrive at destination. Give your battery a chance to to recharge, refer should stay cold for several hours.
Most trucks struggle if successful keeping up camper loads.
So I agree there, you likely arrived with battery already a bit low, shut off truck, switched refer mode/lowered the jacks further draining, then retired. Furnace is also a huge draw. After starting low, running furnace thru night, then you use the jacks again, 3rd largest consumer...especailly if trying all 4 at once.
We also raise and lower jacks (and slide) while truck is running, every little bit helps when your relying on battery.