Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-22-2021, 12:04 PM   #1
Guru
 
Mischief Managed's Avatar
 
City: Hampton Beach, NH
Vessel Name: Mischief Managed II
Vessel Model: 1992 Tollycraft 44 CPMY
Join Date: Oct 2018
Posts: 675
Negative 12V bus

I'm helping out a fellow boater in my marina with some electrical issues on his 36 foot open sportfish style boat. The boat has 4 battery banks:


Starboard engine/house
Port engine
Genset starting
Bow thruster


The boat had horrible galvanic corrosion in the past. The owner installed a galvanic isolator and is hoping that fixed the problem.


Other people have found and fixed starting and dim light problems with the starboard engine/house +12V wiring. AFAIK, they did nothing to the -12V connections


I checked continuity of the bonding bus and -12V bus to the battery banks. Only the starbard engine/house bank -12V has good continuity to the bonding a -12V buses. The other three banks have 55 to 75 ohms of resistance from the -12V battery posts to the bonding and -12V buses.



I don't see any deliberate connection made between the -12V battery posts to the bonding and -12V buses on the other three banks. It seems like any "continuity" (55 to 75 ohms) is purely by chance.



I plan to recommend adding a bus bar and 5 wires, one to each battery bank -12V post, and one to the existing -12V bus (it's too small to connect properly-sized battery cables to). This will tie everything together at the batteries. Any reason not to do this?
Mischief Managed is offline   Reply With Quote
Old 09-22-2021, 01:32 PM   #2
Guru
 
twistedtree's Avatar
 
City: Vermont
Join Date: Jan 2013
Posts: 10,095
I think your approach to creating a common negative bus is a good one.


BTW, galvanic corrosion comes from stray DC current, not stray AC. So your focus on the DC is the right place to be looking. A positive DC wire exposed to bilge water is a classic source of corrosion, so check wiring to bilge pumps, bilge pump switches, etc.
__________________
MVTanglewood.com
twistedtree is online now   Reply With Quote
Old 09-22-2021, 04:06 PM   #3
Guru
 
kchace's Avatar
 
City: Brookline, NH
Vessel Name: Shalloway
Vessel Model: Defever 44, twin Perkins
Join Date: Sep 2013
Posts: 2,260
There should be one central ground bus where all - connections can be traced to. All batteries, all engine blocks, etc. A sub-bus that traces back to the central neg bus with one cable is good. for the purposes of bonding 55-75 ohms is practically open.

Ken
kchace is offline   Reply With Quote
Old 09-22-2021, 06:26 PM   #4
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,191
For bonding it should be 1 ohm or less. I would also pull every connection off and make sure they are both clean and tight.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 09-23-2021, 12:10 AM   #5
Guru
 
SteveK's Avatar
 
City: Gulf Islands, BC Canada
Vessel Name: Sea Sanctuary
Vessel Model: Bayliner 4588
Join Date: Jul 2019
Posts: 5,017
Quote:
Originally Posted by twistedtree View Post
I think your approach to creating a common negative bus is a good one.


BTW, galvanic corrosion comes from stray DC current, not stray AC. So your focus on the DC is the right place to be looking. A positive DC wire exposed to bilge water is a classic source of corrosion, so check wiring to bilge pumps, bilge pump switches, etc.
this LINK
Quote:
GALVANIC CORROSION on the other hand is an electrochemical reaction that causes electrons to flow from one metal to another metal.
STRAY CURRENT CORROSION is simply corrosion caused by stray (leaking) current from a bilge pump or a battery charger among other things.
Stray current might be either AC or DC through the bonded ground wire > shore power > another boat > water. IMO (This is a tough subject)
Quote:
Recent tests have shown that AC current from shorepower in the water can also cause corrosion to underwater parts although at a much slower rate than DC
__________________
SteveK
You only need one working engine. That is why I have two.
Sea Sanctuary-new to me 1992 Bayliner 4588
SteveK is online now   Reply With Quote
Old 09-23-2021, 06:15 AM   #6
Guru
 
Mischief Managed's Avatar
 
City: Hampton Beach, NH
Vessel Name: Mischief Managed II
Vessel Model: 1992 Tollycraft 44 CPMY
Join Date: Oct 2018
Posts: 675
So the boat owner in question does not pussyfoot around (he's a retired merchant marine captain). After sharing my advice, he offered to pay me really well to do the work right away, went to Hamilton Marine and got all the stuff necessary to make a good ground bus, and a couple of hours later I had the work complete. I have decided to start accepting work like this when I have free time, it's easy money for me and there's a huge demand for this kind of work in my marina. I don't "need" the money, but it's nice.
Mischief Managed is offline   Reply With Quote
Old 10-11-2021, 08:09 PM   #7
Guru
 
foggysail's Avatar
 
City: Ashland, MA
Vessel Model: 1990 Silverton 40 aftcabin
Join Date: Jul 2016
Posts: 1,208
Quote:
Originally Posted by Mischief Managed View Post
So the boat owner in question does not pussyfoot around (he's a retired merchant marine captain). After sharing my advice, he offered to pay me really well to do the work right away, went to Hamilton Marine and got all the stuff necessary to make a good ground bus, and a couple of hours later I had the work complete. I have decided to start accepting work like this when I have free time, it's easy money for me and there's a huge demand for this kind of work in my marina. I don't "need" the money, but it's nice.
I highly recommend you research using a half bridge such as a silver-silver chloride and actually MEASURE the voltages between it and EVERY bonded ground on the boat.

I use a single divers plate style aluminum anode mounted onto my boat's transom. All of my exposed metals are bonded to the boat's grounding system. If metals are deteriorating at a slow pace, most likely the problems are galvanic; if at a rapid pace the problems are usually the result of unwanted currents in the water.
foggysail is offline   Reply With Quote
Old 10-13-2021, 07:48 AM   #8
Guru
 
Mischief Managed's Avatar
 
City: Hampton Beach, NH
Vessel Name: Mischief Managed II
Vessel Model: 1992 Tollycraft 44 CPMY
Join Date: Oct 2018
Posts: 675
Quote:
Originally Posted by foggysail View Post
I highly recommend you research using a half bridge such as a silver-silver chloride and actually MEASURE the voltages between it and EVERY bonded ground on the boat.

I use a single divers plate style aluminum anode mounted onto my boat's transom. All of my exposed metals are bonded to the boat's grounding system. If metals are deteriorating at a slow pace, most likely the problems are galvanic; if at a rapid pace the problems are usually the result of unwanted currents in the water.

I may eventually do that, but only if I need to. At this point everything is working (read below), so I won't waste his money looking for problems he's not having.


The owner had the boat hauled last week and the anodes were about 20% to 30% depleted after a full season in the water, so it seems the galvanic isolator solved his original corrosion issues. Ironically, I learned that I was the person, via a middle-man, that suggested that he put the galvanic isolator in. One of the professional boat repair people at the marina had asked my advice about a boat that had bad corrosion issues last year and I recommended firstly making sure there was a galvanic isolator installed. Turns out this is the same boat he was working on...



I did some electrical installation work for him yesterday and the owner reported to me that all of his electrical stuff is working better than ever, so I am guessing the ground bus I installed solved some other issues too. Sadly, I found quite a lot of random non-boat-wire installed by the factory in his boat and lots of poorly made crimp connections. I fixed what I could, but I suspect he will eventually discover more electrical problems. The boat is headed to the Bahamas for the Winter soon, so he will have ample opportunity to uncover new electrical problems. At least his battery, starting, charger, ground, nav lights, horn, and helm electronics wiring is all checked out and good.
Mischief Managed is offline   Reply With Quote
Old 10-13-2021, 07:59 AM   #9
Guru
 
Seevee's Avatar
 
City: st pete
Vessel Model: 430 Mainship
Join Date: Sep 2016
Posts: 3,502
Excellent thread about checking grounding, which is often the problem in DC circuits.
__________________
Seevee
Seevee is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 09:23 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012