Batteries & Typical 12V Amp Draw

Hi, Christina. Sorry to be blunt, but they're just outright wrong about 6v batteries being any more fragile than 12v. More like the opposite. 6v batteries (at least, real deep cycle ones) are made much more robust than the typical 12v batteries people buy (car batteries and so-called "marine" batteries), because they're made to be used in heavier-duty equipment like golf carts that need a lot of guts and have long, slow discharge and charge rates like we have in campers. If they've seen a lot of bad ones it's due to lack of maintenance/bad installation/faulty equipment/abuse. Normal, below-the-Arctic-Circle cold does not hurt a battery if it's kept charged. If you just let them sit there uncharged all winter, yeah it'll do 'em in eventually. But my four, cheap Duracell EGC2 6-volters from Sam's Club have been sitting in a mostly unused and unheated camper for three Maine winters (so far) without a hitch, because they're on constant, temperature-compensated solar charging. In my four batteries, I add a total of maybe three quarts of distilled water every four months or so. I don't check them that often, and they've never lost enough water to get close to the tops of the plates. Basically, they are maintenance-free.

Some other things to consider:

The more you bounce your batteries around, the more you need better batteries. It's how well the cells are connected internally. My friendly solar expert HandyBob ranks them, in descending order of quality, Crown, Trojan, Deka (who make my Duracells in PA), and lastly, Interstate. I'm rubber-mounting mine to help lessen the vibration. On top of a squishy-but-firm rubber mat-for-standin'-on-at-work from Lowes.

A single 12v battery has to weigh about the same as the two 6-volters to get the same capacity, sometimes more.  Which means you might have to move a 120lb battery around instead of two 60-pounders... And a sealed battery weighs more per amp-hour than a wet battery.

All batteries need to be vented. All lead-acid batteries gas when being charged, the chemistry is no different if it's sealed. They avoid gas reaching pressures that would burst the battery by lowering the charging voltage to make for less gassing, which means slower charging, a big disadvantage if you're depending on limited sunlight for charging, or you don't want to run the generator twice as long. It also means that you have to match the charger more carefully than you do for "wet" batteries. Most chargers and converters don't even work at high enough voltages or for long enough to properly charge a wet battery, so overcharging them with a converter or charger is hard to do (which admittedly has its own problems when using a converter). Sealed batteries are the finicky ones, though.

Sealed batteries are not "maintenance-free", they are "maintenance-prevented." You cannot test the state of charge by sticking a hydrometer in the acid, which is the only truly accurate way to test charge. A voltage check is a very rudimentary check and potentially very innaccurate, because the voltage of a battery fluctuates depending on whether it's being charged or not, or even how long it's been since it reached full charge. And you can't add any water when they need it, all you can do is use them until they fail.

The cost per amp-hour for sealed batteries is way higher, and they provide less capacity per-pound. The only time I could see them being a good choice in a camper is if you had to mount them sideways or something.