Not sure what you mean but it is possible to connect two batteries together, positive to positive and negative to negative if that's what you mean. In practice though I would prefer to swap them over when one goes flat so that I have a better idea of my power usage and if I change a battery over I know I need to reduce my consumption. You can get the flat battery recharged while using the other one too rather than get two flat batteries.
Apparently, and I don't know how accurate this is, connecting a 110 ah battery and an 85 ah battery will not give 195 ah either, although technically it should.
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Do I assume you don't use EHU at all and reliant on the batteries?
Although it's possible, I'd avoid doing unless both batteries are the same capacity (as mentioned). You'll have an imbalanced discharge for one of the batteries and it may drop too deep to recover properly and fail early.
If you do need two seperate batteries, I'd continue using them as you are.