Until they’re connected to the frame of the RV it really doesn’t matter. However, terminal to terminal contact with a metallic object is to be avoided. I now use an insulated ratchet wrench from Harbor Freight when hooking up RV batteries. https://www.harborfreight.com/14-in-drive-teardrop-composite-ratchet-62619.html
It is also possible to put batteries in backwards in battery powered flashlights and other portable electronics. Usually there are markings indicating the polarity of the batteries to be installed but as I get older, I find it increasingly difficult to see the markings and I really like Mikes suggestion of taking a quick pic before removing the batteries to make reinstalling them easier and safer.
Should not wear metal (jewelry) working around anything electrical (not just batteries). or even around a lot of machinery
True that!
I wear my dressy watch and gold wedding ring only on date nights. The rest of the time I wear a very nice silicone ring and no other jewelry.
Oh the stories I could tell about gold wedding rings.
When connecting batteries in parallel. Which polarity should be connected first
Until they’re connected to the frame of the RV it really doesn’t matter. However, terminal to terminal contact with a metallic object is to be avoided. I now use an insulated ratchet wrench from Harbor Freight when hooking up RV batteries. https://www.harborfreight.com/14-in-drive-teardrop-composite-ratchet-62619.html
It is also possible to put batteries in backwards in battery powered flashlights and other portable electronics. Usually there are markings indicating the polarity of the batteries to be installed but as I get older, I find it increasingly difficult to see the markings and I really like Mikes suggestion of taking a quick pic before removing the batteries to make reinstalling them easier and safer.