They are almost certainly 12V which are wired + to + and - to -, ie parallel. If they are 6V they would be wired +, -, +, -, ie in series but 6V are unlikely, particularly for OEM/dealer installed batteries.
I see that the post above made it crystal clear. BTW some batteries, SLA (AKA starting batteries) and AGMs have no watering holes. But they are still wired the same way.
David
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