Electrical issue question

Retired tool maker here with only basic electrical knowledge so looking for expertise. Recently discovered a parasitic electrical draw on my house batter in my aluminum boat. Battery held charge all winter being disconnected and was new last early fall. Hooked everything back up getting ready for summer season and noticed the battery dropping charge within a week or two. Added a disconnect switch and batter holds as long as disconnected.. While booking things back up I noticed a small spark when my wrench on the neg post touched the hull. Used my meter and with neg lead in neg post and pos lead touching hull I am getting my battery voltage on the meter. If I put the red lead on pos post and neg lead on the hull...nothing... Tried unhooking accessory leads one at a time and recheck with no change until all accessory leads were disconnected then the 12.8 v reading went away ...started hooking up accessory leads back on one at a time, no change until all leads were back on and the 12.8 shows up again off the hull. Not sure where to check from here !
All accessories work fine, radio, SS radio, fish finder, lights, bilge pump etc, no issues. The switch will stop the battery from dropping, but why am I getting a 12.8v reading between neg post and hull ?? Or...am I looking for a problem that isn't there ? Any suggestion would be greatly appreciated, thanks.....

Was the last accessory you removed, also the last accessory you added back in? If so, that might be the culprit.

Positive voltage on the hull is odd. I'd disconnect the motor from the battery until you have it figured out. Don't want to smoke any expensive electronics in that.

Getting a current reading off the hull would worry me too electrolysis is no joke. Could there be a nick somewhere on a positive wire where it comes in contact with the hull? Is your bilge pump automatic? I've had float switches in the auto bilges kill batteries.

flatheadsteve said:

Getting a current reading off the hull would worry me too electrolysis is no joke. Could there be a nick somewhere on a positive wire where it comes in contact with the hull? Is your bilge pump automatic? I've had float switches in the auto bilges kill batteries.

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Thanks for your ideas, can't say if there is an auto float switch or not. The boat has never leaked a drop, I only test the pump on each outing. Going to try some additional testing that others have suggested, keeping figures crossed.

Did some additional testing, found that the hull is not charged when the battery switch is on ( battery connected) , but when the switch is off then I get the 12.8v reading from the hull. Tried pulling fuses but nothing until all are pulled .
Removing one at a time then reversing adding one at a time on the accessory wires did nothing until all were out or all were in. I am lost....apparently there is no current thru the hull when house battery is connected, but when disconnected the hull is charged. No sign of any corrosion anywhere in or on the hull, so this issue has just started. Open to any recomendations, thanks in advance !!

Is your disconnect in the positive lead, or the negative lead?

Roger

Pic of setup?

GTS225 said:

Is your disconnect in the positive lead, or the negative lead?

Roger

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Negative post on the battery

Lost But Happy said:

Pic of setup?

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I will get one tomorrow, group 29 deep cycle battery for my house battery. All accessories have wires with inline fuses attach d to the threaded post. Used the same disconnect switch , attached to the neg post that I used on my motor home to disconnect power when in storage.

GTS225 said:

Is your disconnect in the positive lead, or the negative lead?

Roger

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I also posted this issue on another forum and some claimed the shutoff should be on the positive post !!! Instructions on pkg and internet search stated negative post.....which one is correct ?

airshot said:

I also posted this issue on another forum and some claimed the shutoff should be on the positive post !!! Instructions on pkg and internet search stated negative post.....which one is correct ?

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I was thinking that when I read your post above. I don't have any dis-connects, but all circuit breakers and master panel power are on the positive.

I don't know how it would cause your problem though. Maybe some thought in the morning will help. Maybe feeding back through the motor ground?

airshot said:

I also posted this issue on another forum and some claimed the shutoff should be on the positive post !!! Instructions on pkg and internet search stated negative post.....which one is correct ?

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ABYC says +

Also (-) switch disconnect, in a few failure modes, would not disconnect anything.

airshot said:

I also posted this issue on another forum and some claimed the shutoff should be on the positive post !!! Instructions on pkg and internet search stated negative post.....which one is correct ?

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Mine is on the positive. I have a blue seas battery switch and the instructions had the pos wires running to the switch.

Rewire your switch to the positive but double check that your electronics are wired with the correct polarity before powering up.

So you have a house battery connected to all your accessories.

How is it connected to the starter battery or motor?

10" from house battery, there should be circuit protection, what size is it?

InSaneFisherMan said:

So you have a house battery connected to all your accessories.

How is it connected to the starter battery or motor?

10" from house battery, there should be circuit protection, what size is it?

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House battery is not connected to the motor in any way. Seperate starting battery. All accessories have inkine fused leads directly to the house battery.

This is really interesting now....does anyone realize how many videos, written articles and pkg instructions for disconnect switches have oposing statements about pos and neg wiring !!

I have never had this problem, but I believe the positive side should be switched so you're cutting the voltage rather than disconnecting the ground. All you're doing is moving the switch to the positive side so there should be no danger to the electronics. But that doesn't explain the meter reading between the battery and the hull.

Does your stereo have preset AM/FM stations? If so the memory pulls power 24/7.

airshot said:

I also posted this issue on another forum and some claimed the shutoff should be on the positive post !!! Instructions on pkg and internet search stated negative post.....which one is correct ?

Click to expand...

If memory serves me correctly, NHRA says drag cars shall have it in the positive lead. Take that for what it's worth. I was going to ask about the possibility of a starting circuit being on that battery, but that's been covered.
Bailey Boat may have hit the nail though, with his query about the stereo.
SOMEWHERE, you're seeing some kind of continuity bypassing that disconnect, or you wouldn't see a voltage reading.

Roger