2020 F350 6.7 weak start

So took it to the auto parts store up the street. He unhooked one of the batts so each would be isolated when testing the cranking amps. Driver's side was good and had a full 750. Passenger side wouldn't even read, just came back with a code that said "replace battery". He emailed me the results. So I call the dealership. They are happy to look at it today but they said it's not an easy process. Apparently they have to put it on a Ford specific battery machine to try and fully charge it and then test to see if it holds the charge. Said it could take up to 2 hours unless it comes back with a bad battery code quickly. The guy at the auto parts store said I may be ok getting just one battery as I may have caught it in time and the driver's side has the full 750 CA's. Not crazy about the idea but I would bet dollars to donuts that Ford won't replace the one good one.

I did ask the dealership what sort of test they did when I brought it in the other day and they kept it for 2 days. He stammered and said wasn't sure. Translation: they never tested it - or at least they never isolated them. This is why I hate dealing with dealerships. Spend all that money on a truck and can't bother to even try to diagnose an easy thing like a battery. So I have to waste more of my time and take it to get it tested somewhere else and back to the dealership again and wait til it's fixed.