[JRTJH]

You can certainly find "true deep cycle 12 VDC batteries" but they typically cost significantly more than "6 volt golf cart batteries".

Buying "marine/RV deep cycle batteries" is NOT buying a "true deep cycle battery". If the battery has "CCA" listed on the label, it's a "HYBRID" battery with thinner plates and is designed to deliver high amperage to start an engine (and also provides a sustained low level output for RV use)...

As always, no product can be "good at everything".....

A "Car battery" has very thin plates and is designed to provide a "HIGH BURST" to start an engine. But won't survive repeated deep discharge without failure.

A "marine/RV battery" has "slightly thicker plates with holes drilled in them (or a stamped mesh" surface) to increase the surface area" to obtain that "burst power" while having thicker plates that don't warp as easy as automotive batteries, but still can't survive repeated deep discharge without failure, but won't fail quite as fast...

True Deep Cycle batteries have fewer plates, but they are thicker and not as much surface area (they don't need to provide "BURSTS" of power) so the plates are less subject to warping and collecting hydrogen bubbles (which cause corrosion/sulfation which damages the plates rapidly. That means they can survive repeated deep discharges without failure. In other words, they are more "durable and reliable" in an RV environment.

While you can buy 12 volt deep cycle batteries, typically they'll cost much more than golf cart batteries. So essentially, if you're looking to increase the available storage capacity, you can equip your trailer with two "high priced 12 volt batteries or you can accomplish essentially the same thing with two golf cart batteries, usually for around half the price.

Don't get me wrong. You can certainly buy a single deep cycle 12 volt battery and improve your dry camping experience. You can buy two to further improve your dry camping time. Those batteries will usually cost around $175-200 each. With selective (wise) shopping, you can get almost the same energy storage capacity with two 6 VDC GC2 batteries, usually available at Sam's or COSTCO for less than $100 each.

If you're going to go to a "two battery system" the issue isn't "fighting a 6 volt system", it's having more than one battery on the tongue. Whether it's two 6 volt ones or two 12 volt ones, that hassle is exactly the same.