Last year the alternator died on my truck. Of course at night in the middle of no where.
If you don't know on a modern diesel truck you have about 15-20 minutes of runtime after that your truck will die.
I pulled over and checked it, no output.
I started my RV generator and let it back feed to my truck. I towed to a rest area spent the night and continued the next day for another 200 miles.
It won't last long when your electric brakes are in use.
You can have all the portables you want, I love my built in onan.