alternator wiring mystery - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 04-18-2008
Senior Member
 
Join Date: Sep 2007
Posts: 171
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
hertfordnc is on a distinguished road
alternator wiring mystery

30 year old boat with 20 HP yanmar- some time ago the alternator was converted to a Delco - it currently has a 10SI 60 amp Delco alt used on most chevy cars in the 70's.

The field voltage had been wired directly to the starting battery- makes no sense- drains battery even with all switched off.

I wired it to a spare breaker - works great- except.....

If I select the starting battery , which happens to be a bit weak at the moment- the breaker for the alt pops a few seconds after the engine is running. The alternator still makes charging voltage even after it loses the exciter voltage.

If I start the engine from the larger bank- which happens to be fully chargerd, the breaker does not pop.

I don't know the rating of the breaker.

So, my guess is that the lower voltage from the weaker battery draws more amps for the exciter voltage and the higher draw pops the breaker.


Is that logical?

thanks
__________________
In over my head?
First Boat, a well-equipped 1977 Camper Nicholson 31
What is all this stuff and how does it work?
Reply With Quote Share with Facebook
  #2  
Old 04-21-2008
Lancer28's Avatar
I'm the FNG still...
 
Join Date: Jul 2007
Posts: 397
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Lancer28 is on a distinguished road
Somewhat.

I think you should re-wire your exciter voltage to a hard line to the starting battery (or to the battery switch would be an even shorter run).

The alternator draws just a fraction of a milliamp and doesn't really kill the battery like you'd think. Non-use maintenance is to visit the boat once a month or every other month and run the generator or charger for a couple of hours. If the battery is dying sooner than that, it is probably not good.

The cycle for the alternator above is something like this Start-wait about 5 seconds-RPM up-go into exciting mode (creates a LOT of draw and power loss for a minute)- then it charges max amps at about 14.75 volts until the battery starts to top off, then it goes to about 5 amps and lowers output voltage.

You're probably popping the breaker from drawing too much through the wire to recharge the dead or bad battery. I do know that a lot of delco alternators didn't push full amperage unless the line voltage was below a cetain point. you may have one of those.


Unwire the breaker -- if the battery is bad replace it, don't crutch. check the wiring to the battery and terminals for cleanliness and resistance too. If this is the one with the voltage regulator built into the back of it, you should run the lead all the way to the battery terminal itself, then the charge leads are ok going to your battery switch. You should also have a line that goes to ground coming off the back with a lamp in series to show when the alternator is not charging. Check to see if that lamp is operating or not too, if you can't get a good ground then the charging system greatly suffers or stops completely.

Hope that helps! Charging systems are a total pain in the ass unless you've owned the boat since it was born!
__________________
Robert

I reject your reality and substitute my own.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #3  
Old 04-21-2008
Lancer28's Avatar
I'm the FNG still...
 
Join Date: Jul 2007
Posts: 397
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Lancer28 is on a distinguished road
another thought - 60 amps is REALLY high for just a 20hp motor. You may be nearly killing the engine trying to recharge your batteries. If you were caught with your pants down in an emergency and needed full throttle, that alternator would likely make the engine bog down bad.

I would suggest going to a mitsubishi 20-25 amp with built in regulator to reduce the parasitic horsepower loss when your bateries are low. Anything should bolt and wire in as long as the hinge bolt and pattern matches your old delco. (replacement is only about $40 at autozone).
__________________
Robert

I reject your reality and substitute my own.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #4  
Old 04-21-2008
camaraderie's Avatar
moderate?
 
Join Date: May 2002
Location: East Coast
Posts: 13,877
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 15
camaraderie is a jewel in the rough camaraderie is a jewel in the rough camaraderie is a jewel in the rough
Lancer...60 amps is only a couple of horsepower. He is not killing anything.
__________________
No longer posting. Reach me by PM!
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Mystery: or Can 25 Gallons Pour Down my Mast? lbdavis Gear & Maintenance 13 04-29-2008 07:37 PM
Oil Pressure Mystery Solved bsfree Gear & Maintenance 5 12-21-2007 07:23 PM
Mystery on Long Island Sound timeline - Connecticut Post NewsReader News Feeds 0 03-29-2007 06:15 PM
FARALLON ISLANDS Missing sailor mystery Boaters' speculations ... - San Francisco Chronicle NewsReader News Feeds 0 02-03-2007 10:15 AM
Mystery Deepens in New 'Lost' Episode - San Francisco Chronicle NewsReader News Feeds 0 10-12-2006 11:15 AM


All times are GMT -4. The time now is 08:15 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.