Well I do don't have solar panels so might not be much help. Your two 12 volt batteries are already in parallel. Meaning you already have a cable tied to both positive terminals and a cable tied to both negative terminals. With this being said, I do not think it would not make any difference. Just be sure you hook positive to positive and negative to negative AND you are connecting to 12 volts.
1997 Triple E Empress, Freightliner Chassis, CAT 3126 w/ 275 horse's.
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