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Old 25-02-2021, 20:11   #1
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Battery charger produce hight DC current derivation to the aluminum hull when connect

Right now I am in a marina in Panama on the ground with my recently brought aluminum boat. I had spend days controlling the derivations of currents DC to the hull. When I though I have all under control, I start to measure a 60-70 mA of negative DC current to the aluminum hull. I have disconnected and search for the dam leak and found that when I disconnect the battery charger the reading goes back to the all ready hight 9 mA.
may anybody have the same experience.
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Old 25-02-2021, 20:46   #2
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

Where are you measuring this?
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Old 26-02-2021, 05:34   #3
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

I take the readings from the positive bus bar to the hull.
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Old 26-02-2021, 06:59   #4
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

You have probably already checked and cleaned all of your ground (-) connections. There could also be a break in a ground cable or connector, may be worth testing continuity of all the ground wires?

Problems like this are no fun! Good luck!
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Old 26-02-2021, 09:35   #5
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

I would check out Attainable Adventure Cruising's website. Articles on aluminum boats, very knowledgeable and clear articles about such issues as yours. A membership may be worth it. I've made good use of mine.
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Old 26-02-2021, 12:31   #6
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

You may also have some dissimilar metals in contact with each other and the water such as bronze thru hulls or stainless steel plates creating small currents that you measure. I have not owned an aluminum boat but I would make certain that the quantity and quality of the zinc anodes is sufficient to protect your hull.
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Old 26-02-2021, 21:32   #7
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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Originally Posted by Perolito View Post
I take the readings from the positive bus bar to the hull.
That does not make sense. You mean from the neg?
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Old 26-02-2021, 22:07   #8
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

You may be on the current scale but you are not reading current between the Positive buss bar and ground. You are actually reading a voltage difference. Put your meter on volts, plug the probe into the voltage reading input. Read the voltage and report back here what it is.

To read current the meter must be in series with the load.

If your ground is totally isolated from the hull you should read zero. Somewere you have a connection between the hull and an electrical circuit.
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Old 27-02-2021, 04:51   #9
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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Originally Posted by SV_Sweet_Ruca View Post
You have probably already checked and cleaned all of your ground (-) connections. There could also be a break in a ground cable or connector, may be worth testing continuity of all the ground wires?



Problems like this are no fun! Good luck!


Thank you for your replay. Yes I have check all connections and ground cables. This is way a Think is more a problem of the marina installation.
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Old 27-02-2021, 04:54   #10
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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I would check out Attainable Adventure Cruising's website. Articles on aluminum boats, very knowledgeable and clear articles about such issues as yours. A membership may be worth it. I've made good use of mine.


Thanks for the suggestion, I will look at their page. I think is a very good advise, specially for me, with small knowledge of the aluminum.
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Old 27-02-2021, 04:58   #11
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Battery charger produce hight DC current derivation to the aluminum hull when connect

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That does not make sense. You mean from the neg?


Is very simply, I measure connecting the positive terminal of the multimeter to the positive of the battery and the negative to the hull, using the scale of mA a have a hight readings when using the charger, around 60 or 70 mA.
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Old 27-02-2021, 05:11   #12
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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You may be on the current scale but you are not reading current between the Positive buss bar and ground. You are actually reading a voltage difference. Put your meter on volts, plug the probe into the voltage reading input. Read the voltage and report back here what it is.

To read current the meter must be in series with the load.

If your ground is totally isolated from the hull you should read zero. Somewere you have a connection between the hull and an electrical circuit.


I have done this, and I read 7-8 volts on the voltage DC scale.
And yes I have look in all connections but don't find enything wrong. What I think is the marina have a problems with their grounds?
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Old 27-02-2021, 05:16   #13
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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Originally Posted by Perolito View Post
I have done this, and I read 7-8 volts on the voltage DC scale.
And yes I have look in all connections but don't find enything wrong. What I think is the marina have a problems with their grounds?
I can not be the marina because with an aluminum boat, you must have an isolation transformer. Also, you need to have a silver chloride reference to measure accurately: Corrosion Reference Electrode Product Specifications
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Old 27-02-2021, 06:35   #14
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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I can not be the marina because with an aluminum boat, you must have an isolation transformer. Also, you need to have a silver chloride reference to measure accurately: Corrosion Reference Electrode Product Specifications
That is the correct way to test however that must be done in water.

The OP suggests he is on the hard ?

"Right now I am in a marina in Panama on the ground"
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Old 27-02-2021, 10:19   #15
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Re: Battery charger produce hight DC current derivation to the aluminum hull when con

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Originally Posted by Perolito View Post
Is very simply, I measure connecting the positive terminal of the multimeter to the positive of the battery and the negative to the hull, using the scale of mA a have a hight readings when using the charger, around 60 or 70 mA.

So you have created a new path that did not exist without the meter. And measured current in that non existent path. Which means nothing. This only works if you remove an existing wire (path) and measure what was going through the existing path.

If you put your amp meter between the battery pos and battery neg you will also get 1000ísof amps. And blow up the meter. That does not mean you have a problem. It means you created a new path with the meter that was not there before.
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