[WJQ]

If your batteries are lead acid batteries, they are 6 volts batteries if they have three battery caps. If they have 6 caps, they are 12 volts. If they are six-volt batteries, they are connected in series to give you 12 volts for your RV. One of the responses above told you to connect the charger to the + on the battery that connects to the RV power center and the - on the other battery. If they are 12-volt batteries, they are connected in parallel. Then you can connect to the + and the - on either battery.

If you have 6-volt batteries you are fortunate as that arrangement is arguably better but I won't go into why. Try Googling 6-volt versus 12-volt RV batteries and I bet you get a lot of hits. I am sure this forum has addressed that question many times.

Note, some batteries do not have caps so measure the battery voltage. If you have lithium batteries, they will be wired in parallel and you are most fortunate.