Charging dual battery systems

[tassietriton]

Sorry to post a boat question but...
I have just bought a new (secondhand) boat.
It has a dual battery sytem controlled by a round dial which has the following settings;
0
1
2
1+2.
I have a good battery charger which can be set to "trickle" charge over the winter months.
If I connect 1 of the batteries to that charger on "trickle" should I set the dial to that battery or 1+2?
Any advice would be appreciated.

[Mikew]

Connect the battery charger to the positive and negative on your motor (disconnected) and put the dial on 1+2
If you only connect it to one battery it will only charge that battery as the earth is not shared.
Hope this helps