Common Ground??

[flippin Dan]

Book that came with new trolling motor says I need a common ground to prevent corrosion and electrolysis and it would improve detail on sonar. I have the cranking battery and 2 more wired for 24 for trolling motor. To do this would I tie all 3 negative terminals together?

[flippin Dan]

Got it.

[slonezp]

Was it a buss bar located in the boat somewhere?

[Traveler2586]

Was it a buss bar located in the boat somewhere?

I guess we'll never know....

 

It would be interesting to see how many of us are using a common ground as opposed to independent systems.

 

Motorguide suggest a common ground.

 

Here's one source of info (but I think the diagram is confusing)  http://www.mikesreelrepair.com/schematics/albums/motorguide/battery_wiring/commomground.pdf

[Fishing Rhino]

I seem to recall many years ago that an auto electrical guy told me that some cars used a "common ground" which in the case of lights was the body and frame.  The lights only had a positive wire running to them.  Other cars used a two wire system with a positive and a negative line for each light.  Maybe it was the other way around, but that was the first time, and until now, the last time I heard that term used.

 

The engine, body and frame were connected by ground straps.  The ground straps, when they had a problem would cause a failure of many electric circuits.

[flippin Dan]

Motor guide said connect grounds to same terminal and I was thinking hook negs together with a jumper because someone did that in my old boat between crank and trolling. Why I have no idea. After thinking for a bit I figured it would be better to go to a ground bar. I have not checked but will call a dealer/mechanic next week to see if it is already that way.

[Traveler2586]

I seem to recall many years ago that an auto electrical guy told me that some cars used a "common ground" which in the case of lights was the body and frame.  The lights only had a positive wire running to them.  Other cars used a two wire system with a positive and a negative line for each light.  Maybe it was the other way around, but that was the first time, and until now, the last time I heard that term used.

 

The engine, body and frame were connected by ground straps.  The ground straps, when they had a problem would cause a failure of many electric circuits.

Your correct, back in the day of all metal cars the body and frame was used as the return path (Common Ground for the negative potential); but when they started coming out with composite body's they had to run twin lead to those areas that were insulated from the chassis ground.

 

We had a 30' wooded cabin cruiser that had the negative terminal of the batteries connected to the engine block, rudder shaft, through hull anode, fuel tank, electrical buss, etc.; it was a job going over that system every spring.

[Fishing Rhino]

Your correct, back in the day of all metal cars the body and frame was used as the return path (Common Ground for the negative potential); but when they started coming out with composite body's they had to run twin lead to those areas that were insulated from the chassis ground.

 

We had a 30' wooded cabin cruiser that had the negative terminal of the batteries connected to the engine block, rudder shaft, through hull anode, fuel tank, electrical buss, etc.; it was a job going over that system every spring.

 

I also seem to recall that we had a 55 Mercury that was positive ground.  I think it was also a six volt system.  I believe Ford changed to twelve volt in '56, maybe '57.  I think that was when they changed to negative ground.

[Wayne P.]

Attaching a wire between the trolling motor negative and the starting battery negative is one of the resolutions suggested to combat RFI with sonar units. That is called a Ground Loop.

 

Never, ever, connect ALL the battery negatives together if you have a 24V or 36V trolling motor. ONLY connect to the battery negative where the trolling motor negative (black wire) is connected.

[Traveler2586]

Attaching a wire between the trolling motor negative and the starting battery negative is one of the resolutions suggested to combat RFI with sonar units. That is called a Ground Loop.

 

Never, ever, connect ALL the battery negatives together if you have a 24V or 36V trolling motor. ONLY connect to the battery negative where the trolling motor negative (black wire) is connected.

 

X2,

 

Also a word of CAUTION IF YOU ARE USING AN ON-BOARD CHARGING SYSTEM.  Consult your charging system user manual BEFORE connecting a Common Ground (CG)

 

Since my post #4 I've realized I failed to consider that some of us have on-board charging systems that may not like the TM negative connected to the starting battery negative to form a CG.  If your systems user manual does not address the use of a CG, contact the manufacture for guidance BEFORE DOING ANYTHING.

 

I'll take this as an action item and will contact Pro Charging Systems for their input.

[BassnChris]

 

I'll take this as an action item and will contact Pro Charging Systems for their input.

If you don't mind, please let me know what they say?

Thanks

[Wayne P.]

Some on-board chargers will blow the ground fuse in a Minnkota bow motor.

 

Know your equipment before you randomly connect stuff togther based on a generic statement.

 

One more thing, is with some installations, that ground loop may be the cause of poor sonar performance.