Powering a camper from a Bluetti

Last year we purchased a Bluetti EB150 just before leaving on a camping trip. We ended up at a campsite that did not have power available, so we plugged the entire camper into the Bluetti to power a CPAP and the recharge the coach batteries. We woke up to a temperature of 9°F with the 12V coach batteries very low and the Bluetti almost drained. The furnace had run much of the night, draining the coach batteries. The next night we ran the CPAP directly from the EB150 and only plugged in the camper as needed.

Here is my question. Is anyone aware of a way to use the 12V outlet of the Bluetti to recharge the 12V coach batteries. In my experience powering 120 volts is only half as efficient as powering 12 volts. Would it be as simple as clipping something like jumper cables to the correct posts on the coach batteries powered by the Bluetti 12 Volt outlet? I believe the outlet from the Bluetti is as high as 14 Volts.