I will warn you that with 12 volt batteries even pictures are not always the do all end all, You MUST mark clearly the POSITIVE and NEGETAVE in the photo,, Make a sign and lay it atop the battery before you click the pic.
Here is why
As I said before.. you can get a Group xx in, usually, 3 (or more) Configurations
|=====|
|A . .|
| . .B|
|=====|
|=====|
| . . |
|A . B|
|=====|
Now Depending on the battery group SUFFEX, A may be Positive or Negative,, This is why the passing RVer said "Mine are hooked up the other way" His battery is hte reverse of teh O/P's. so at a glance, it appeared to the other person the O/P's battery was backwards.
Happned to me when I bought a new battery for my car.. The specified battery was a different suffex, so they put it in backwards. Was kind of impressive, Still have not figured out what smoked.