When we are doing service on chargers or batteries the negative wire is the first off last on. This seems to be the way most techs do it.
This is actually a cross over from Automotive. The Neg OFF and ON first is because should you slip with the spanner on the positive terminal and short to the chassis, the isolated earth will of course mean no sparks will fly or worse, such as welding the spanner to the chassis.
Patrick, I will assume you have a portable charger and want to keep the batteries trickle charged. Is that correct?? Trickle is not the best way to go, but seeing it is just the winter, you will get by. If the charger does not have trickle charge ability, DO NOT leave the charger permanently switched on. It will boil the batteries.
I also assume you are using the battery selector switch so as you can charge both the house and start bank. Also not the best practice, but once again, it wil get you buy over winter.
So how did you do this when in the water
??? I would have thought the same scenario would have sufficed.
And finaly, connect all your cables
, then as chuck described,with everything firstly off, turn on the main breaker and follow with the required breakers through to the circuit controlling the charger.
Oh and ALWAYS make sure you connect and disconnect charger leads with charger turned off.