Mystery Potential

[Jim Ewing]

I just put in a new 12 volt outlet so while I was working on the wiring I disconnected all the batteries at the negative terminals and switched the battery selector to OFF, the shore power was disconnected. When I put my voltmeter between a hot lead and a (supposedly disconnected) ground I read 6 volts?????!!!! Obviously, I've got an electrical leak someplace but it seems strange (to me anyway) that the potential would be 6 volts. Has anybody run into anything like this in their boating adventures?Thanks,Jim"Prospect"

 

[Steve Dion]

Probably seeking it OWN ground!

Jim:I would guess that the system was seeking it's own ground. I doubt that this would happen if the POS. term was disconnected. You may just try it and see.

 

[R.W. Landau]

Solar panel?

Jim,Do you have a solor panel and is it connected. Mine use to put out 6 volts in the cabin before I would put it on deck. r.w.landau

 

[Jim Ewing]

Ah yes...

The solar panel may be the culprit. Although I thought it would be disconnected with the switch set to off, maybe not. It was cloudy day which would account for the constant low volt reading.Thanks for the suggestion, I'll check it out.Jim"Prospect"

 

[Rick]

Grounding thru prop

When you disconnect the neg your voltage still seeks ground thru the engine/shaft/prop to the water. A better test would be to hook your neg back up and disconnect the pos. With all equipment off check for current between the pos post on the battery and the disconnected pos cable. Any current flowing is caused by equipment still on or stray voltage leak to ground.Dont leave your neg disconnected for long. The current grounding thru your prop shaft is rapidly dissolving your zincs (if they are in good condition) or you are galvanizing your prop and shaft.I recommend Nigel Calders book "Boat Owners Electrical and Mechanical Systems".

 

[John Visser]

Really?

I find it hard to believe that current would flow out of the positive terminal of a battery that has its negative terminal connected to nothing, because the electricity was "seeking it's own ground." (This was asserted in the previous and the first replies to this topic). Can someone please explain this?Thanks,jv