What's the difference in these setups?

[Sinkoumn]

So I'm going with three batteries in the boat - two optima blues on the main side for all the goodies, and then a starting battery on the other side . They are separated by a hellroaring isolator/combiner.

The problem just started when I put the extra optima in the system (so the second blue-top in the main side), I had both main batteries 'almost' fully charged (around 12.1V on the voltmeter); the starting battery was a strong 12.4V). I left the boat sit on the lift overnight, came down to lower the boat and the winch on the lift wouldn't budge because my two optimas were dead...however, the starting battery was still fully charged.

NOTHING was turned on in the boat, so would this be a grounding problem? Do I need to run ground wire from the second optima directly to the block? Or can I just run it to the negative post on the first battery, then right to the block? see photo, too much of a pain to try and describe.

But aren't both setups below are the same in terms of grounding the system? Or not? I just don't know where the **** there is a drain in the system to drain both batteries overnight. :x (this never happened with one starting battery, and one main AUX battery)

[MHayes]

Re: What's the difference in these setups?

I left the boat sit on the lift overnight, came down to lower the boat and the winch on the lift wouldn't budge because my two optimas were dead...however, the starting battery was still fully charged.)

So your boat lift is connected to the batteries in your boat? First time I've heard of this.

But aren't both setups below are the same in terms of grounding the system? Or not?

Yes, the two diagrams that you posted are the same in terms of grounding. The ground should not be the issue for your batteries going dead. There is obviously a drain on your batteries somewhere, maybe the boat lift?

[Sinkoumn]

RE: Re: What

Yeah, the boat lift gets the power off of the batteries in the boat - I just connect the cables when we raise/lower the boat, once done I disconnect it and tuck the cable into the side compartment (it has worked great for the past three years).

But the winch is never connected to the boat overnight, so it can't be the culprit for what is draining the battery. I'm going to see if the battery is dead again when I go back up north, but this has never happened before I added the second battery to the main side...hmmm :x

[Laptom]

RE: Re: What

Check if there is no draining current from the 2 battery's with an amp meter.
It could be possible if 1 of the 2 battery's connected to eachother is not 100% it would drain itself and the other. This will go faster with 1 good and 1 bad battery in parallel then just the "bad" battery alone.

[Andrew]

RE: Re: What

definetly sounds like a slightly weaker battery is draining the stronger one

[TravelinTrav]

RE: Re: What

So the isolator is between the "Starting Battery, and the Blue Optima" and now you added another battery that ties directly to the blue optima. Now with the extra optima you find both of them drained over night. I agree with the other posters, your new battery is holding a charge longer than the older, and thus the older is pulling charge from the newer until it reaches higher charge, and they play a tug of war type battle for the charge, until there is none. I would get another isolator, and install it between the two optimas, so all three batteries are seperated from eachother when there is no charge.

[Andrew]

RE: Re: What

or just get an isolator designed for 3 batts