Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 15-07-2019, 10:45   #1
Registered User

Join Date: Jun 2018
Location: Adriatic
Boat: Bavaria 46 (2007)
Posts: 100
Alternator intermittently not charging

Hi all, I have had an issue recently with my alternator.

In the last week, it will be working one moment and then then it will stop charging the batteries. The first time it self corrected but now itís just happened again.

I have checked the batteries and they are ok.

There is 16v coming from the +ve and -be terminals of the alternator.

Any hints where to check next? Would this suggest a faulty voltage regulator? Any way to confirm?
__________________

lawrence_craig is offline   Reply With Quote
Old 15-07-2019, 11:32   #2
Registered User

Join Date: Jun 2018
Location: Adriatic
Boat: Bavaria 46 (2007)
Posts: 100
Re: Alternator intermittently not charging

It might be worth mentioning that I have a diode splitter. However the both the service and starter batteries are not being charged.
__________________

lawrence_craig is offline   Reply With Quote
Old 15-07-2019, 11:36   #3
Registered User

Join Date: Jan 2015
Location: Victoria BC
Boat: 1980 Hunter 36
Posts: 953
Re: Alternator intermittently not charging

I had a similar issue and it turned out a washer had fallen into the alt (!) and was grounding the diode pack
__________________
S/V Gudgeon
www.gudgeonblog.ca
alctel is offline   Reply With Quote
Old 15-07-2019, 11:48   #4
Registered User

Join Date: Jun 2018
Location: Adriatic
Boat: Bavaria 46 (2007)
Posts: 100
Re: Alternator intermittently not charging

Little bit of an update, I have 16v going from alternator to the split diode, 12.2v from the diode to service (same as measured at batt) and 12.6v at the diode to the starter (same as measured at batt).

Would that suggest itís the diode?
lawrence_craig is offline   Reply With Quote
Old 15-07-2019, 11:54   #5
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 11,409
Re: Alternator intermittently not charging

"Split diode" is not something Im familiar with. This is not part of the bridge rectifier, but external to the alternator?
belizesailor is online now   Reply With Quote
Old 15-07-2019, 11:56   #6
Registered User

Join Date: Jun 2018
Location: Adriatic
Boat: Bavaria 46 (2007)
Posts: 100
Re: Alternator intermittently not charging

Quote:
Originally Posted by belizesailor View Post
"Split diode" is not something Im familiar with. This is not part of the bridge rectifier, but external to the alternator?


Itís for splitting the charge to the service and starter batteries as below.

Click image for larger version

Name:	IMG_7024.jpg
Views:	76
Size:	88.4 KB
ID:	196009
lawrence_craig is offline   Reply With Quote
Old 15-07-2019, 12:22   #7
Registered User

Join Date: Jul 2016
Location: East Coast USA
Boat: Boatless at the moment
Posts: 445
Re: Alternator intermittently not charging

It does suggest there's a problem with the diode splitter, but 16v coming from the alternator also suggests a regulator problem. Depending on the type of diodes used in the splitter you should see a voltage drop of 0.2 VDC to 1.4 VDC on the output terminals.
kenbo is offline   Reply With Quote
Old 15-07-2019, 12:43   #8
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 11,409
Re: Alternator intermittently not charging

Quote:
Originally Posted by lawrence_craig View Post
Itís for splitting the charge to the service and starter batteries as below.

Attachment 196009
Interesting, Im more familiar with combiners/relays etc.

Doesnt sound like its part of the issue, so two other usual suspects are the bridge rectifier or the regulator.

A quick simple test is to VERY briefly touch a lead from the battery to the field terminal on the alternator with enine running. Alternator should go immediately to full output capacity at that RPM. If it goes full output then its likely the regulator. If not, then it could be the bridge rectifier. Test by testing each diode.

Another likely source is wiring...could be simple like a disconnected field/B+ wire. Check connections/continuity.
belizesailor is online now   Reply With Quote
Old 15-07-2019, 13:10   #9
Senior Cruiser
 
DeepFrz's Avatar

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 8,407
Re: Alternator intermittently not charging

It looks like bad diodes. Dropping 4 volts across the diodes is not normal. .4 volts maybe. Did you measure the voltage across the diodes? If that is okay then there is a bad connection/cable in the circuit. The reason the alternator voltage is so high is because, I assume, the sense voltage is read at the battery and is trying to get the voltage at the battery up. Better than diode splitters are the new charge combiner relays. Well, they aren't new but they did replace the diodes because of the voltage drop.
DeepFrz is offline   Reply With Quote
Old 15-07-2019, 13:33   #10
Registered User

Join Date: Jun 2018
Location: Adriatic
Boat: Bavaria 46 (2007)
Posts: 100
Re: Alternator intermittently not charging

Quote:
Originally Posted by DeepFrz View Post
It looks like bad diodes. Dropping 4 volts across the diodes is not normal. .4 volts maybe. Did you measure the voltage across the diodes? If that is okay then there is a bad connection/cable in the circuit. The reason the alternator voltage is so high is because, I assume, the sense voltage is read at the battery and is trying to get the voltage at the battery up. Better than diode splitters are the new charge combiner relays. Well, they aren't new but they did replace the diodes because of the voltage drop.


I think youíre right. I have just literally bypassed the diode (alt straight connected to service batt) and I am now charging the service batteries. With 14.3v from alt and 13.8v to service.
lawrence_craig is offline   Reply With Quote
Old 15-07-2019, 17:26   #11
Senior Cruiser
 
DeepFrz's Avatar

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 8,407
Re: Alternator intermittently not charging

Good.

While you are replacing the diodes, hopefully with an ACR or equivalent, I would suggest that you take the time to clean and closely inspect all of your connections in the charging cct.

https://www.bluesea.com/products/cat...harging_Relays
DeepFrz is offline   Reply With Quote
Old 15-07-2019, 20:48   #12
Registered User

Join Date: Jun 2013
Location: canada
Posts: 2,713
Re: Alternator intermittently not charging

Sounds like the diode splitter if you have 16v in and 12.2 out. (Which is just the battery voltage.) Remove the alt wire from diode splitter and connect direct to one of the battery wires on the other posts . See if it will directly charge one battery.
smac999 is offline   Reply With Quote
Old 15-07-2019, 20:50   #13
Registered User

Join Date: Jun 2013
Location: canada
Posts: 2,713
Re: Alternator intermittently not charging

Quote:
Originally Posted by lawrence_craig View Post
I think youíre right. I have just literally bypassed the diode (alt straight connected to service batt) and I am now charging the service batteries. With 14.3v from alt and 13.8v to service.
If you are losing 0.5v from alt to battery. Probably time for a bigger alt cable too.
smac999 is offline   Reply With Quote
Old 16-07-2019, 11:03   #14
Registered User

Join Date: Dec 2012
Boat: Jeanneau SO45.2
Posts: 197
Re: Alternator intermittently not charging

Check the ground of the alternator. I had a pot connection at the block which raised the alternator negative by a couple volts above ground, limiting charging even though it had good output.
Redline452 is offline   Reply With Quote
Old 16-07-2019, 13:07   #15
Registered User

Join Date: Feb 2015
Location: Oakland CA, boat on the hard in Panama
Boat: Morgan 46 ketch
Posts: 905
Re: Alternator intermittently not charging

Quote:
Originally Posted by lawrence_craig View Post
Itís for splitting the charge to the service and starter batteries as below.

Attachment 196009
That "splitter" is properly called a diode battery isolator. It has gone bad, causing high voltage drop. Voltage drop should be 0.7V with a silicon diode type and lower about 0.2V with MESFET isolator.

If the Vsense line to your alternator (usually a blue wire) is connected to the output of this faulty isolator or to the battery directly, it is telling the alternator to put out high voltage, 16V in your case, to try to raise the sense voltage to about 13.5V. This is only my suspicion based on your original and subsequent posts.

To test, you may simply bypass each diode temporarily moving the wire coming from alternator over to one of the battery wires connecting to the isolator. Start engine and remeasure voltages at that battery. Should now be around 13 5V depending on what you are using for voltage regulation on the alternator.
__________________

waterman46 is offline   Reply With Quote
Reply

Tags
alternator, charging

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Alternator Cutting Out Intermittently sgtPluck Electrical: Batteries, Generators & Solar 11 15-08-2014 14:54
Autopilot Disengages Intermittently for No Apparent Reason CampDavid Marine Electronics 10 21-02-2012 08:56
Rev Counter Reads Intermittently timj Engines and Propulsion Systems 5 06-06-2011 22:49
Autohelm 4000 Intermittently Dives Port or Starboard senormechanico Marine Electronics 9 08-11-2009 22:17
Losing Power Intermittently When Planing Joe500 Engines and Propulsion Systems 11 08-08-2009 08:39

Advertise Here


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:45.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×

ShowCase vBulletin Plugins by Drive Thru Online, Inc.