Leece-Neville Alternators.

[Rob seadog]

Howdy fellow boaters! I have a problem with my main alternator. It will charge normally for about 3 hours and then, according to my Xantrex batt. monitoring display, there will be no output and instead indicates a discharge consistent with what I am using ie.VHF ,Autopilot etc.The alternator is a Leece-Neville and can put out round 130 Amps. After the engine is shut down, the following day I can start the engine and the alt. will have a normal output of say initially 95A, gradually decreasing to 16A after 15min or so.Does aanyone have any suggestions as to what may be the problem?
Cheers,
Rob seadog.

[fallingeggs]

You put this post in an odd place. I don't think tech support knows alternators! I generally view posting in a time line view, but the smarter folks may not. Ask a moderator to move it. Or just repost in the appropriate forum.

Now if I were to toss out ideas...

Have you confirmed your suspensions with an amp meter?

Do you know what the batteries state of charge is at? What is the capacity of the bank? How old are they? If you are close to 80% SOC with flooded lead acid, you'd expect the amps to drop considerably.

Do you have an external controller? Maybe check its program, voltage sense wire, temp sense, etc.

If no issues there, maybe the alternator is heating up too much causing the controller to decrease the load? An inferred thermometer can help with this.

Cheers!


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[a64pilot]

Moved to electrical, no problem

[skipmac]

My guess is some part of the electronics are shutting down due to heat. Not an expert so couldn't say if it would be the diodes or regulator but probably one of these. I guess it could be in the alternator itself, heat causing a winding to short on something?

If you aren't familiar with electrical work it's usually very easy and cheap to remove and take to an auto alternator shop.

[Stu Jackson]

Could your batteries be full?

[Rob seadog]

Hi Stu, no the batterys voltage begins to decrease and shows a discharge.
Cheers, Rob.

[Rob seadog]

Hi there, thanks for your input. I will do as you suggest Cheers,Rob.

[Rob seadog]

Dear fallingeggs, I am still getting used to this site and will attempt to improve with placement of queries regarding electrical.
Cheers, Rob.

[Rob seadog]

Thanks for moving my query to electrical.
Cheers,Rob.

[witzgall]

Does the alternator have internal or external regulation?

Chris

[Stu Jackson]

Rob, can you give us some voltage readings at these different times?

[Omatako]

If the incoming amps stayed positive even just a couple of amps then it would appear that the internal reg has sensed enough voltage to shut the alt down.

But if there is a outflow of amps commensurate with expected take-off (radio, instruments, lights) showing on the Xantrex display then IMO the alt has stopped working. The output should never go negative if the alt is still functioning.

It's not that unusual for a diode to go US when it gets hot. Or for that matter a circuit going open when hot (fields maybe). Have you tried starting the engine an hour or two after the alt signs off to see if it's back (ie not an ice-cold start).

[Rob seadog]

Thanks for input. I have not tried what you suggest re a 1-2hr delay warm start. I will give it a go on the next leg.Have seond smaller alt. that is for start batt .but can be coupled to the house batts.I will find out if leece-neville alternator has int. or ext reg.
Cheers, Rob.

[Rob seadog]

Hi Stu, when alternator is working normally I see 13.4V on Xantrex display with an input amperage of around 20A. After a 2-3 hrs engine run I see 12.6V with a discharge consistent with running V.H.F and autopilot.(-6 to -8Amps.) From a cold engine start with partially discharged batteries I see 80-90Amps generated.Thanks for your interest.
Cheers, Rob.

[Rob seadog]

Hi Chris, I dont know but will find out.As we live aboard I will have to wait so I can pull up floor boards and generally create chaos. My top priority is to install a second alternator as the existing one just failed due to a small unknown oil leak. The Leece-neville alternator is now working but still a the intermittent fault I have described. Thanks for your interest with this problem.
Cheers, Rob.