I had an issue at an overnight stop recently in a rest area. I'm already planning to replace the batteries in the trailer as they don't hold a charge as long as before, and after just one night of using the lights, fans, and fridge while sleeping they are low.
What I didn't think about is that my Ram has the 7-pin power plug always on, so the truck batteries were trying to keep the trailer batteries changed all night. I wasn't pleased when the truck wouldn't start the next morning.
Fortunately someone who was standing outside their car nearby just happened to have one of those boosters, and after hooking it up I was immediately able to turn over the diesel. New batteries already in the truck, two new 6V batteries in the trailer soon, and I'm pretty sure I won't forget to unplug the trailer from the truck any time I'm stopping for more than a few hours from now on. Even with the new batteries, I'm thinking about getting a booster just for peace of mind when on the road.