Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 10-05-2013, 17:47   #1
Registered User

Join Date: Jul 2009
Location: Ontario, Canada
Boat: Niagara 31
Posts: 252
2/0 wire being burnt from Alternator

I have an Alternator that on it's associated gauge can say it is putting out 90 amps. The alternator output, via a thick wire, is connected to a shunt which provides, via thin wires, the input to the gauge and also, via thick wires, passes back the current to the battery.

The short piece of wire, about 6" long, from the Alternator to the front of the shunt is 2/0 (or 00) gauge. Over two years it has gone solid, black, corroded and burnt off the cover !

The wire from the other side of the shunt, also 2/0 gauge, going to the battery, is perfectly OK. So are the thin wires going to the ammeter.

I have not yet determined whether 3/0 (or 000) gauge wire and associated connectors are available, or whether this is the right approach to replace the 6" long piece of 2/0 wire.

I thought I would like to get some comments from the experts on this forum first !!

Thank you.
__________________

__________________
macbeth is offline   Reply With Quote
Old 10-05-2013, 17:51   #2
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Re: 2/0 wire being burnt from Alternator

High resistance connections. Corroded terminals or bad crimps or whatever. 90A cannot heat the conductor of a 2/0 wire, which is overkill already.
__________________

__________________
daddle is offline   Reply With Quote
Old 10-05-2013, 18:03   #3
Registered User

Join Date: Jul 2009
Location: Ontario, Canada
Boat: Niagara 31
Posts: 252
Re: 2/0 wire being burnt from Alternator

Quote:
Originally Posted by daddle View Post
High resistance connections. Corroded terminals or bad crimps or whatever. 90A cannot heat the conductor of a 2/0 wire, which is overkill already.
High resistance connectors: These are heavy metal connectors, similar to

5 Big Bare Copper Ring Lug Terminal Connectors 2 0 Wire AWG 1 2" Stud Molex | eBay
made of grey metal.

Corroded terminals: Certainly not !

Bad crimps: Whacked with a hammer in a special crimping device which indents some of the metal into the wire.

I'm sorry, I don't think it's that straight forward !
__________________
macbeth is offline   Reply With Quote
Old 10-05-2013, 18:09   #4
Registered User

Join Date: Dec 2010
Location: Wilmington, N.C.
Boat: Marine Trader, Sedan, 40', Donnchaidh
Posts: 21
Re: 2/0 wire being burnt from Alternator

Daddle is correct, there is a bad connection on one or both ends of your 6 inch 2/0 wire. A bad connection will get hot which will increase the resistance making it hotter and so on. 2/0 copper would be good for around 150 amps. J.T.
__________________
awpptdt is offline   Reply With Quote
Old 10-05-2013, 18:35   #5
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: 2/0 wire being burnt from Alternator

6" of 2/0 will be good for well over 150A. I agree, there is a connector issue. If the current wire is now without cover, etc., why not make a new 6" piece and see if it also gets hot? You shouldn't be using it now anyway.

The only other thing I can think of is that somehow the shunt is grounded and you effectively have a short on that side of it.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 10-05-2013, 18:47   #6
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Re: 2/0 wire being burnt from Alternator

Quote:
Originally Posted by macbeth View Post
Bad crimps:[/COLOR] Whacked with a hammer in a special crimping device which indents some of the metal into the wire.
There's the prime suspect.

Trival diagnostic: Using an accurate voltmeter, with the alternator working hard, measure the voltage across the various interfaces.

Burning a big wire implies significant watts being dissipated. 20, 50, 200? So the voltage drop in one of the parts is going to be obvious:

50W / 90A = 0.6V

Measure each of the four interfaces: stud to crimp terminal, terminal to wire, etc.
__________________
daddle is offline   Reply With Quote
Old 10-05-2013, 18:48   #7
Registered User
 
nitpik's Avatar

Join Date: Feb 2010
Location: Canada, North Channel of Lake Huron
Boat: 41' Colvin Gaff-rigged Schooner
Posts: 222
Send a message via Yahoo to nitpik Send a message via Skype™ to nitpik
Re: 2/0 wire being burnt from Alternator

Are you telling us that your shunt is in the Positive alternator feed to the battery? (unusual?)
Daddle suggested the possibility of corroded connections, not connector. The connectors you referenced from eBay should suffice, 'though if in salt water it would be better if they were tinned, and they don't appear to be over-spec'd in terms of wall thickness.
Without laying eyes on the situation, I would tend to agree with Daddle - suspect the connections first.
I hope you are not holding up a hammer-crimped connection as the epitome of fine electrical workmanship? If no Deox or adhesive-lined heat shrink was used, corrosion could most certainly have got in there, and it was not likely a 100% connection in the first place.
__________________
Some days you step in it ............... some days you don't.
nitpik is offline   Reply With Quote
Old 10-05-2013, 18:56   #8
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: 2/0 wire being burnt from Alternator

150 amps is close for 2/0 if you don't account for the run or temperature. You can put a shunt on the hot side if the meter is analog or if digital you add a special type of converter which 'fools" the meter into thinking it is on the negative side. All a current meter does is measure the voltage across the shunt which converts directly into current. I did this with my two alternators so I would know if they are close to being overloaded and to give me an idea of what the load is on my DC system.

You have to make sure you shunt is rated for or greater than the amount of current that is going to be run through it.

There is one way the insulation of your 2/0 wire could have melted and that is if the hot side of your alternator shorts out.

You only need 2/0 wire for your alternator if it capable of producing near 150 amps, and this is dependent on the run where the greater the run the more below a 150 amp alternatior you can justify using 2/0 cable.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 10-05-2013, 19:32   #9
Registered User

Join Date: Jul 2006
Posts: 3,949
Re: 2/0 wire being burnt from Alternator

He said the alternator is putting out 90 amps.
__________________
Kettlewell Cruising
Kettlewell is offline   Reply With Quote
Old 10-05-2013, 19:34   #10
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: 2/0 wire being burnt from Alternator

He didn't say if 90 amps is it rating. I am underway right now with two alternators rated at 110 amps where one is producing 28 amps and the other 24 amps.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 10-05-2013, 21:40   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: 2/0 wire being burnt from Alternator

AWG 2/0 is plenty big enough.

There's definitely a connector problem....loose, bad crimp, or surface corrosion most likely. Could also be dissimilar metals, defective shunt, etc.

The return wire (negative) should be same size as the positive wire, and should go directly to the alternator ground, not the engine.

FWIW,

Bill
__________________
btrayfors is offline   Reply With Quote
Old 11-05-2013, 01:45   #12
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
Quote:
Originally Posted by btrayfors View Post
AWG 2/0 is plenty big enough.

There's definitely a connector problem....loose, bad crimp, or surface corrosion most likely. Could also be dissimilar metals, defective shunt, etc.

The return wire (negative) should be same size as the positive wire, and should go directly to the alternator ground, not the engine.

FWIW,

Bill
+1 high resistance connection between altermator and shunt or a short from shunt to negative. Measure voltage drop, i.e. positive meter-lead to alternator and negative lead to shunt. Voltage should be at or very near 0V.
__________________
s/v Jedi is offline   Reply With Quote
Old 11-05-2013, 05:47   #13
Registered User

Join Date: Nov 2012
Posts: 40
Re: 2/0 wire being burnt from Alternator

Which shunt? Do you have a picture of the installation?

If high resistance was the problem, you'd likely see fretting on one of the terminals. 2/0 wire is PLENTY big. You have another problem.
__________________
dannobee is offline   Reply With Quote
Old 11-05-2013, 06:26   #14
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: 2/0 wire being burnt from Alternator

Quote:
Originally Posted by macbeth View Post
The short piece of wire, about 6" long, from the Alternator to the front of the shunt is 2/0 (or 00) gauge. Over two years it has gone solid, black, corroded and burnt off the cover !
.
If the wire has developed black wire corrosion this may be the problem rather than the connections, but the wire obviously needs replacing so its a bit academic.

A wire connected to the engine with a shunt mounted on a rigid part of the boat needs some thought about vibration protection.
Six inches sounds a bit short to allow for sufficient movement to prevent strain on the joints.
You may consider making it a little longer.
__________________
noelex 77 is offline   Reply With Quote
Old 11-05-2013, 06:54   #15
Registered User

Join Date: Jul 2009
Location: Ontario, Canada
Boat: Niagara 31
Posts: 252
Re: 2/0 wire being burnt from Alternator

Quote:
Originally Posted by noelex 77 View Post
If the wire has developed black wire corrosion this may be the problem rather than the connections, but the wire obviously needs replacing so its a bit academic.

A wire connected to the engine with a shunt mounted on a rigid part of the boat needs some thought about vibration protection.
Six inches sounds a bit short to allow for sufficient movement to prevent strain on the joints.
You may consider making it a little longer.

A. Obviously I'm going to replace it - today ! BTW, it was initially sealed with shrink tube. I'm going to do better this time. And it addition to crimping, I'll solder it, and use copper terminals.

B. The only bad connection I can think of is that there are three wires attached to the Alternator output terminal. I'll move the other two to the other end of the wire, i.e. shunt connection. Also the nut on the Alternator output terminal was a little corroded - it was ordinary metal - I'll change that to SS.

C. Referring to the quote above, yes, the Alternator is on the engine (obviously !!), but the shunt is on the nearby sidewall. I guess vibration could be an issue ?? I'll make a loop this time, making it 9" to 12" long.

D. The alternator is rated at 120amps, but I'never seen the output that high.

E. When I've made the new loop, I'll take the measurements suggested above.

F. The shunt and associated gauge were made for high amps - the gauge's dial goes up to 200 amps !

G. Thanks for opinions ! Any more ?
__________________

__________________
macbeth is offline   Reply With Quote
Reply

Tags
alternator

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 21:04.


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.