NF - Boat Wiring - common ground for 12 volt systems

[John Bacon]

The manual for my trolling motor recommends that 12 volt systems share a common ground between the starting and trolling motor batteries. I.e. the negative terminals of the two batteries should be connected by a wire. But there should not be any connection between the positive terminals.

 

This is supposed to improve sonar display, reduces corrosion & electrolysis, and reduces interference with other electronic equipment.

 

Has anybody heard of this? Does anyone here have the technical expertise to confirm the effectiveness of doing this?

Edited August 30, 2015 by JohnBacon

[aplumma]

The short answer is yes it does. I have a 28ft all aluminum boat that lives in a marina and it is very susceptible to electrolysis. It has an electronic galvanic isolation on the boat. It allows any stray current from the boat or water to pass thru the electrical system and out the ground wire connected to shore power. I also have a meter that measures the current passing thru the water and boat hull to monitor if the anodes need to be changed or the EGI is working correctly.

 

 

 

 

Art

[2 tone z71]

What size wire do they want you to run back to the - ?

[aplumma]

The grounding wire between should be the same size as the main feed to the trolling motor. Just pick up a ground wire from the auto store that is the correct length to go between the 2 batteries. You can use a smaller one but it is not as effective.

 

 

 

Art

[Sinker]

My TM and all other electronics are on two different circuits. TM has nothing else running off it. I don't have my batteries connected at the negative, they are at different ends of the boat......No interference at all.

 

S.

[ecmilley]

Guess it all depends if u have interference dont do it on my boat keep 2 trolling motor batteries on one side and cranking and electronics run other side no issues here.

Do it if you like probably makes bigger difference on tin boats than glass

[DRIFTER_016]

The short answer is yes it does. I have a 28ft all aluminum boat that lives in a marina and it is very susceptible to electrolysis. It has an electronic galvanic isolation on the boat. It allows any stray current from the boat or water to pass thru the electrical system and out the ground wire connected to shore power. I also have a meter that measures the current passing thru the water and boat hull to monitor if the anodes need to be changed or the EGI is working correctly.

 

 

 

 

Art

 

 

 

Not an issue for fresh water boats Art.

A huge issue with saltwater boats though.

 

As long as you have no TM interference with your sonar there is no need to worry about a ground bus in fresh water. IMHO

[John Bacon]

Guess it all depends if u have interference dont do it on my boat keep 2 trolling motor batteries on one side and cranking and electronics run other side no issues here.

Do it if you like probably makes bigger difference on tin boats than glass

 

If you have two trolling motor batteries then I assume that you are probably running a 24 volt trolling motor. If so, you cannot use a common ground. It only applies to to 12 volt systems.

[Spiel]

 

If you have two trolling motor batteries then I assume that you are probably running a 24 volt trolling motor. If so, you cannot use a common ground. It only applies to to 12 volt systems.

 

Not necessarily John, I have 2 12 volt batteries up front (in parallel) for the bow mount electric producing of course 12 volts.

 

Wishing however that I had bought a 24 volt.