SailNet Community - View Single Post - Ground leak?
Thread: Ground leak?
View Single Post
post #7 of Old 09-23-2008
Telstar 28
sailingdog's Avatar
Join Date: Mar 2006
Location: New England
Posts: 43,290
Thanks: 0
Thanked 18 Times in 14 Posts
Rep Power: 16
Originally Posted by patja View Post
Hi, me again. I've done some more troubleshooting and think you are right about the memory on the stereo. I saw this same effect on the battery charger and the inverter...they all show 20 - 50 mA current even when "off". Then I tried lifting the negative return cable from my negative bus for these individual circuits and the current stopped flowing, which I believe rules out a ground leak as the cause for their minor current draws.

I've got things cleared up now so that I am not getting any current flow more than a couple mA when measuring between the positive cables and the battery positive posts.
That's good to hear... that's what it sounded like from your description. Unfortunately, lots of equipment has parasitic current draws when off.

I picked up Charlie Wing's Boatowner's Illustrated Electrical Handbook which suggested an additional test for current leak: measure DC current between the green bonding conductor and the through-hull or other fitting it is protecting. I did this with the easiest item to measure: the springy grounding conductor that rides on the prop shaft. It is showing 30 mA of current. Wing's book (page 88) says even 1 mA is cause for concern on this. I am seeing this current even when I completely disconnect the batteries (remove all positive and negative cables from batter posts). Is this a real cause for concern? Where could it be getting its current? It looks like it is flowing from the bonding wire to the shaft (red/+ multimeter probe is on the bonding conductor, black/common probe is on the shaft).

How are the bonding wires for the boat connected, and to what? Without knowing more about how the boat is setup, it is hard to say what the problem is. It could be coming from outside your boat, from another boat at the marina or a fault in the marina's AC shore power system. Have you tried doing the same test when anchored out in a cove by yourself?? If it is the same there, it is likely due to something on the boat. If not, then it is likely due to something at the marina or on a nearby boat.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

sailingdog is offline  
Quote Share with Facebook
For the best viewing experience please update your browser to Google Chrome