Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-04-2013, 17:53   #1
Registered User

Join Date: Oct 2010
Location: Cooktown Queensland Australia
Boat: Herreshoff H36 12.8m
Posts: 46
Electrolysis

I have raised all of the negative cables above ground to the steel hull. I have a multi meter and a digital clamp meter. I have used the 2K and 20K ohms on the multi meter to check the grounding on the negative side. I rectified 4 problems and the multi meter on the two settings show no fault. On the 200K and the 2M settings it shows a fault.
How do I check the positive cables to see if I am getting any stray earth?
Advice would be appreciated.
__________________

__________________
Ray Perry is offline   Reply With Quote
Old 09-04-2013, 18:02   #2
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by Ray Perry View Post
I have raised all of the negative cables above ground to the steel hull. I have a multi meter and a digital clamp meter. I have used the 2K and 20K ohms on the multi meter to check the grounding on the negative side. I rectified 4 problems and the multi meter on the two settings show no fault. On the 200K and the 2M settings it shows a fault.
How do I check the positive cables to see if I am getting any stray earth?
Advice would be appreciated.
You can do the same with the positive side , just disconnect the battery

Note resistance tests are problematic in determining cause as at higher ohms settings you can be injecting tiny currents. Equally you could have insulation breakdown at 12v that you mightn't see

What are you trying to find and fix ?

Dave
__________________

__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 09-04-2013, 18:05   #3
Registered User

Join Date: Oct 2010
Location: Cooktown Queensland Australia
Boat: Herreshoff H36 12.8m
Posts: 46
Re: Electrolysis

Hi Dave,
My zinc blocks are not lasting and I am getting paint bubbles above and below waterline.
__________________
Ray Perry is offline   Reply With Quote
Old 09-04-2013, 18:10   #4
Registered User
 
surfmachine's Avatar

Join Date: Jul 2009
Location: Cruising the West coast of Sumatra and the offshore islands, surfing!!
Boat: Feltz Skorpion mark 11A, Aluminium 39' sloop, constructed Hamburg. http://photobucket.com/eloise_01
Posts: 674
Images: 9
Send a message via Skype™ to surfmachine
Re: Electrolysis

Hi Ray.
What I did was connect a 12v led, with resistor, from positive bus to the hull.
It glowed brightly, indicating a current leakage to the hull via the negative bus.

Then, disconnected each postive feed from the positive bus in turn until the led went out. Then checked the positive and negative wires to the item.. Found several faults.

Mainly on wiring to the sender units on the motor for temp guage. Also, vhf antenna braid was broken and touching inside of the mast. Tye this?

Cheers from Keith.
__________________
Keith, "But I was born very young and grew up knowing little of the world!" http://surfmachine-surfmachine.blogspot.com.au/
surfmachine is offline   Reply With Quote
Old 09-04-2013, 18:23   #5
Registered User

Join Date: Oct 2010
Location: Cooktown Queensland Australia
Boat: Herreshoff H36 12.8m
Posts: 46
Re: Electrolysis

Hi Keith,
Thanks very much for advice. Can you give me more info on the LED and size of resistor?
__________________
Ray Perry is offline   Reply With Quote
Old 09-04-2013, 23:35   #6
Registered User
 
surfmachine's Avatar

Join Date: Jul 2009
Location: Cruising the West coast of Sumatra and the offshore islands, surfing!!
Boat: Feltz Skorpion mark 11A, Aluminium 39' sloop, constructed Hamburg. http://photobucket.com/eloise_01
Posts: 674
Images: 9
Send a message via Skype™ to surfmachine
Re: Electrolysis

How to Wire LED Lights to 12-Volt Auto Wiring | eHow.com

Use a 470 ohm resistor in series on one leg of the led, drill a small hole in the fuse panel and leave the led poking through as a permanent fixture.

How to Wire LED Lights to 12-Volt Auto Wiring | eHow.com

Cheers from Keith.
__________________
Keith, "But I was born very young and grew up knowing little of the world!" http://surfmachine-surfmachine.blogspot.com.au/
surfmachine is offline   Reply With Quote
Old 10-04-2013, 10:42   #7
Marine Service Provider

Join Date: Dec 2003
Location: South Carolina
Boat: Philip Rhodes Custom
Posts: 395
Re: Electrolysis

It is extremely unlikely that your zinc problem is related in any way to the 12 volt system inside the boat. You are tilting at windmills, fixing the wrong problem.

Your first line of defense is a Galvanic Isolator in the ground lead of your shore power connection. It is only a $100 expense and can pay for itself in one year of zinc savings.

Once it is installed, measure the AC voltage across it. The paint bubbles you describe are a symptom of AC leakage that forms bubbles of sodium hypochlorite under the paint. If the AC voltage is greater than about 0.5 volts you need to troubleshoot problems in your AC wiring and add a Galvanic Capacitor across the Galvanic Isolator to bypass the AC current if needed.

Rather than trying to isolate the battery system, there is less chance of DC electrolysis from the battery causing problems if ALL the negative connections are solidly bonded to the hull. That way they have to be at the same voltage as the hull and minimize introducing extra problems.

I lived aboard a steel boat for nearly 15 years, send me an email to tech@yandina.com if you have any questions.
__________________

__________________
Andina Marie is offline   Reply With Quote
Reply

Tags
electrolysis

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:37.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.