maximizing battery capacity

When I upgraded my Grp 24 to a Costco Grp 27 Marine/RV battery, I went from 75AH to 115AH. And I think there are Grp 29 and 31 above that.

29, 30, 31

Same battery, different posts.

The common 12 volt battery group sizes do differ in physical size and capacity.

For instance, here's a Group 27 deep cycle 12 volt battery:

http://www.fullriverbattery.com/product/batteries/DC105-12

And here's a Group 31 deep cycle 12 volt battery of the same series by the same manufacturer. Note that it has larger physical dimensions and greater capacity:

http://www.fullriverbattery.com/product/batteries/DC115-12

Both of the above two diffferent group size batteries have the same type of terminals.

I have to say for myself anyway I find it a bit overwhelming how much there is to learn about an rv electrical system when solar is involved. Thank you Almot for dumbing it down for me a bit. I now have a better understanding and see that I do have some options for more battery capacity given the limitations of room I need to endure. The Torklift battery cradle thing is an idea but might be a hinderance when going off-road. I like the idea of AGM because the can be mounted on their side making the best use of space in my battery house. Too bad lithium batteries cost so much. Ton of amp hours in a smaller lighter package but cha-ching$$$

Lithiums and AGM are 2 different things.

If you can squeeze 2 AGM on its side for a total 200-220 AH, with moderate energy use and 200W solar you'll be OK. Can present technical difficulties though. The battery sides are not always perfectly flat.

Don't cheap out on AGM, get some reputable brand. Lifeline may not be the best choice for the reasons that people noted. Deka is a decent brand too, and costs less.