Battery Charger Leak AC

[deltafishing]

Good evening everyone,

I have a pretty interesting problem that hopefully has an easy solution =). About two months ago, I installed a MinnKota dual bank onboard charger for my 2 group 27 trolling motor batteries. The charger is located at the rear of my boat and batteries are located up front. While running the power cords for the batteries, I tried to keep them isolated from my transducer wires as it said in the manual that it may cause interference; which it did. When I turn on my bow mount trolling motor my fish finder showed a bunch of distorted vertical lines. So I read up on the issue (should have came here first!) and per the MinnKota website, if intereference is happening then a ground wire can be ran to the negative battery post on the cranking motor. In my case, I own a North River where everything is grounded to a negative bus bar then grounded to the hull. The ground wire is a 10 gauge wire fused to 1 amp. Anyhow, this immediately eliminated any further distortion and everything seemed to be going well. Fast forward to this past weekend. I decided to test my downrigger cables to see what the natural voltage of the line is and what I saw was pretty weird, it first started out at .7 volts then dropped for a minute or so to settle around .51 volts. I'm not sure if it would have kept dropping over time. Then today while my boat was hooked up to the charger (extension cord from my house to boat while on the trailer) I stuck the positive lead on my boat and negative on the trailer and my multimeter read .8 volts AC. Did I mess up hooking up the ground wire to my negative bus bar? Can or would this cause permanent damage? Any suggestions on what or how I can isolate the boat from AC current, or is this a concern? Sorry if it's all over the place, let me know if I need to clarify something. Thanks guys!

[deltafishing]

Forgot to add, I do have an aluminum anode on the boat and on both my main and kicker engines.

[MacGyver]

" I own a North River where everything is grounded to a negative bus bar then grounded to the hull. The ground wire is a 10 gauge wire fused to 1 amp"
****************
The ground going from the neg bus bar to the hull should be as large as the battery neg cable and DO NOT FUSED IT.

The charger should be grounded to the AC ground to remove any stray AC. Measure the resistance from the AC ground terminal to the charger neg wire... is it shorted? Next check the extension cord is it grounded to the charger?

[deltafishing]

Sorry for not being clear, the ground wire from the busbar to the hull is 4 ga non fused wire (same as batt cables). The 10 ga fused wire runs from the trolling motor battery negative post to the bus bar.

[Aluminum Clone Owner]

yes

[MacGyver]

I don't think it will help at this time. A galvanic isolator is design to STOP a DC voltage below 1.2v and pass any AC voltage.

Your measuring the AC voltage between the hull and the trailer. This may be normal because the trailer could be floating because it not grounded to the hull. Also 0.51v AC is not a lot of voltage when using a DVM (1 meg ohm input resistance).

Is the power cord going directly to the charger or does it go through the boat AC power panel first?

[Aluminum Clone Owner]

deleted

[Mtb55]

I own a North River where everything is grounded to a negative bus bar then grounded to the hull. The ground wire is a 10 gauge wire fused to 1 amp.

First off I need to say I am not an aluminum boat wiring expert by any means, I just lurk around here to learn best practices to help me keep my aluminum boat in good shape. Your above statement caught my attention, I have always read that the negative bus bar should be grounded to the negative battery terminal not the hull. Hopefully someone more knowledgeable than I will shed more light on this if I am wrong.

[kmorin]

Mtb55, the way I read delta's post is: there are two busses, one is common to DC + and the second common to DC- and the DCneg buss is bonded to the hull in one location? (that is my understanding of the wording?? subject to correction, of course.) That is the accepted practice to keep the hull from being at a different potential (voltage level) than the DC power system.

Note the two wire marine DC power systems' discussion is sure complicated by using the term "ground" since there isn't any involved - that is no ground. There are two legs of DC and AC and they both return to 'zero' potential to avoid stray current into the hull buttttt... however..... the chassis Should be bonded to avoid "leakage" or high resistance DC-Neg current flow in some electronics, some engines, and some deck hardware. When you include the term and connection of a bond and then use the term "ground" for DCnegative polarity- the discussion rapidly goes down hill into confusion on most boards.

This discussion is very similar to discussions of the three types of corrosion in aluminum- if accurate and unique terms are not correctly applied; the causes will not be understood and therefore discussions about helping/curing/repairing/stopping corrosion becomes somewhat chaotic or at least confusing.

So, I'm encouraging a close look at the terms and meanings we all use while discussing marine wiring. I believe the American Boat and Yacht Council's standards for DC electrical installations in metal boats describes just such a practice in the wiring system described above?

Cheers,
Kevin Morin
Kenai, AK

[Chaps]

The neg bus bar is connected to the neg terminal on your battery as well as the hull but don't use the hull as a random dc neg connection point for any 12v devices