Troubleshooting stray voltage tips...please

[Michael.redmon]

I bought a 1987 bass tracker TX-17 last summer. I am pulling my hair out with something. I got a mild shock when touching the side of the boat while barefoot the other day. I think in boats that is a bad thing. I have spent about 5 long hours trying to pinpoint where in the heck the problem is. It appears that the ground wire runs from the battery to the bow, back to the steering wheel area for all the accessories. I have pinpointed which battery it is coming from (I have 3 batteries...#1 for the starter, #2 for the trolling motor in series, and #3 for the trolling motor and accessories). When i disconnect the negative lead on #3 the stray voltage does not exist. I have taken all fuses out of the fuse box and i still get 12 volts of voltage when touching a battery positive lead and the hull with my voltmeter. I have tried, as best as possible, looked for chafing of any wires. I do not see anything grounding to the hull. I am about to just run a new negative wire but it is going be a pain getting in a few places. I am at the end of my rope. Would you guys have any advice on how to troubleshoot this damn thing! Thanks in advance for tips you can provide. Mike

 

[UncleWillie]

... I got a mild shock when touching the side of the boat while barefoot the other day. ...It appears that the ground wire runs from the battery to the bow, back to the steering wheel area for all the accessories.... When i disconnect the negative lead on #3 the stray voltage does not exist....I still get 12 volts of voltage when touching a battery positive lead and the hull with my voltmeter...

The Hull should be connected to the Battery NEG Lead. So 12v from Battery POS to the Hull should Always read 12v. Completely normal and expected.
You must be extremely sensitive to Voltage as most people can not detect 12v DC at all. Was it a DC or an AC shock? I can barely feel 48v DC.

Did you have ANYTHING connected to AC in the boat at the time? Battery charger? Trouble Light? Radio? Cooling Fan? Extension cord? ANYTHING?

Where was your OTHER Foot? On Shore? In the Boat?

Was the boat in the Water or on a trailer? If in the water, it is possible the leakage is from another boat near you.

 

[Michael.redmon]

The boat was on the trailer. I couldn't feel the voltage with my hands but I felt it with my forearms. It is a small aluminum boat so no ac just dc. I thought current running through the hull would cause electrolysis....I'm a totally clueless?

The Hull is not connected to the NEG battery side. I am under the impression that you cant hook boats up like cars or airplanes.....you can not use the hull to ground the electronics. It was a DC shock. No AC. Battery charger not hooked up. No radio, no cooling fan. Nothing. Both feet on the garage floor. Boat on trailer.

Thanks

 

[bruceb58]

You need to answer all of Uncle Willie's questions.

 

[UncleWillie]

Just to make sure we are perfectly clear....

The boat was in the garage and the only thing contacting the Boat/Trailer assembly were the two tires and the Jack wheel touching the floor. No car attached.
There was no extension cord or any other power source anywhere in or near the Boat/Trailer/Car assembly.
You approached the boat with bare feet and placed your hand on the boat and felt a DC shock. So far Correct?

Unless a special effort was made to isolate the battery NEG from the Hull is is nearly certain that they are connected somewhere.
Likely more that one somewhere. Again Perfectly Normal.
Just mounting the engine to the transom would be a major connection point.

There is a confusion between the terms GROUNDED and BONDED. Electrically the two process are the same.
The hull is Bonded to the Battery NEG. An Ohm meter will show the Hull and the Battery Neg terminal are connected.

That being said, you are correct the you should not GROUND anything to the Hull like is commonly done in a car.

Example: If you wanted to add a radio ....
In a Car, you would connect the radio to 12v power and attach the radio's ground to the body of the car for a grounded return path.
In a Boat, you would connect the radio to 12v power and attach the radio's ground to the Negative Power Bus of the boat, not to the Hull.
You do not want to carry actual current through the hull like you commonly do with a car.

The shock took place between the Boat and the Earth, not inside the boat.
Measure the Voltage, AC and DC, between the boats hull and a puddle of water on the garage floor.
Yes!, Stick the meter lead in the Water puddle.

What did it read? Both AC and DC.

 

[Splat]

This is a strange one. I'll be interested in what's causing this. I'll also add, or ask, the engine wasn't running correct? My bets at this point are a open neutral in the house somehow finding a difference in potential in the concrete slab, or the motor was running, and a leaky rectifier is to blame.

 

[UncleWillie]

This is a strange one. I'll be interested in what's causing this. I'll also add, or ask, the engine wasn't running correct? My bets at this point are a open neutral in the house somehow finding a difference in potential in the concrete slab, or the motor was running, and a leaky rectifier is to blame.

It IS a strange one! And it also makes no sense based on the information given. That is why I Really like this one! :joyous:

A leaky rectifier in a running boat in the Garage would also make no sense. Carbon Monoxide would be the bigger danger here.
The Alternator/Battery Current wants to return to its source, the Alternator/Battery on the boat. Not the garage floor.

The devil is in the details. And there is a detail of this picture that is still missing.

 

[bruceb58]

I am guessing there was a battery charger attached. Almost has to be. If that's the case, the fault is in the charger or the house wiring...not the boat.

 

[Michael.redmon]

OK, sorry for the incomplete information. Thank you for your help so far.

I need to clarify some things:

1. When I got the mild shock the onboard battery charger was plugged in and charging. I disconnected the charger and tested the voltage and got/still get 12 Volts DC.

2, I checked all my wiring today by disconnecting everything but the engine starter. 12 Volts DC still when using voltmeter between hull of aluminum boat and positive battery lead. Zero volts DC whenever the negative lead is disconnected.

3. I poured water and tested between the boat hull and water puddle: zero AC volts and minimal voltage DC (.03 on the 20 volt scale).

So, am I to gather this is normal and i am trying to fix a bonding issue that doesnt matter? I dont want my 1987 Bass Tracker to corrode away...it's old but it is all i have

Thanks in advance for your knowledge and patience

Mike

 

[Michael.redmon]

So to say it again: if i can read 12 volts between a hot battery lead and by touching the negative probe of the meter to the aluminum hull, does that mean i have a problem?

 

[UncleWillie]

So to say it again: if i can read 12 volts between a hot battery lead and by touching the negative probe of the meter to the aluminum hull, does that mean i have a problem?

So to answer it again, :joyous: You do Not have a DC Grounding/Bonding problem! It is Completely Normal!

Post #2
The Hull should be connected to the Battery NEG Lead. So 12v from Battery POS to the Hull should Always read 12v. Completely normal and expected.

Post #5
Unless a special effort was made to isolate the battery NEG from the Hull is is nearly certain that they are connected somewhere. Likely more that one somewhere. Again Perfectly Normal.

Your shock was AC when the charger was attached.
Hook it back up the same as it was and measure from the hull to the puddle again.

Are you using and extension cord with a missing ground pin?

 

[Michael.redmon]

Willie, Thank you. I got a lot of practice soldering, crimping, volt metering today. Stupid is my middle name!!!!!! At least I semi understand how jacked up my electrical accessories are...winter project I suppose The charger and the cord have 3 prongs.

 

[UncleWillie]

In re-reading this thread I found in post #3 a very critical statement from you....

... I thought current running through the hull would cause electrolysis...

That is a very key point about Bonding.
The Hull is connected to the Battery NEG Post but nothing else is. There is NO current running through the hull.
The Hull becomes an electrical Dead End. It is Bonded/Grounded but not used to power anything.

The Hull becomes the equivalent of the Bird on the High Voltage Power Line. It is connected but no power flows through it.

 

[bruceb58]

Next question is what kind and how old of a battery charger are you using?

 

[Michael.redmon]

i will have to look today after work...not that old really.

 

[midcarolina]

Before you go throwing what could be a perfectly good charger out the door.............. try and replicate the exact scenario again, plug the charger in the same receptacle , make sure charger is charging, pour water on floor...........but this time instead of using your body as the test light use your meter set to AC volts.

one meter lead to puddle and other to boat........If you read any voltage plug charger in a different recep. that is NOT fed by the same breaker and recheck puddle to boat..........If no reading that means you have a issue with shop wiring........

 

[bruceb58]

Adding to what Midcarolina is saying, I would take that same extension cord plugged into the charger and measure the voltage between the ground and neutral of the cord to the water puddle. Measure on AC. Should be close to zero.

 

[UncleWillie]

Before you go throwing what could be a perfectly good charger out the door.............. try and replicate the exact scenario again, plug the charger in the same receptacle , make sure charger is charging, pour water on floor...........but this time instead of using your body as the test light use your meter set to AC volts.
one meter lead to puddle and other to boat........If you read any voltage plug charger in a different recep. that is NOT fed by the same breaker and recheck puddle to boat..........If no reading that means you have a issue with shop wiring........

On the surface that sounds reasonable... Then, On second thought ...

Assuming the battery charger does NOT have a fault;
I can't think of any scenario where a fault in the house wiring would produce any currents in the secondary of the battery charger.

Floating Ground.... No.
Reverse Polarity... No.
Hot Ground .... Maybe! But that would have knocked him on his Butt if it didn't kill him outright. It would also have been noticed a long time ago.

 

[bruceb58]

That's why I want to know what battery charger he has too. Metal case sitting against the side of the boat with a ground that has some slight voltage on it. Depends on what it is plugged into, if its a secondary power panel, neutral not bonded to ground at the panel...list goes on.

Took until post #9 to find out there was a battery charger plugged in! This is a potentially dangerous condition here!

 

[midcarolina]

On the surface that sounds reasonable... Then, On second thought ...

Assuming the battery charger does NOT have a fault;
I can't think of any scenario where a fault in the house wiring would produce any currents in the secondary of the battery charger.

Floating Ground.... No.
Reverse Polarity... No.
Hot Ground .... Maybe! But that would have knocked him on his Butt if it didn't kill him outright. It would also have been noticed a long time ago.

The charger or the house power is the culprit.................It is not a 12 volt issue, one or the other needs to be ruled out. then by default it is the other.

That's called trouble shooting 101 process of elimination.....

Non of us are there......... I do not know the site conditions, for all I know the garage/shop is fed from the house by an extension cord buried by 2 inches of sand...........who knows......