I removed the shelf then put them side-by-side.
I installed an 2nd battery and then a 3rd battery because I learned they are only 30AH each... that resulted in total of 90AH - which I could only use 45AH before damaging them. The three were also very heavy and I needed to replace water monthly... no way I could get to the filler holes with that shelf there.
When we take our next trip, I'm replacing all three with a cheap
single LifePO4 100AH lithium and I can use the
entire 100AH plus it
weighs about 25 lbs and I can
reinstall the shelf. This is what I recommend.