Alternator Blues

[jfkal]

My boat "eats" alternators faster than I sandwiches. I use simple car type internal regulated alternators. They have only two contacts (Ground & +) and one plug for the charging lamp. + is connected to the batteries via splitting diodes and I am using a ZAP STOP across the terminals. Neverttheless all alternators just die on my after an few weeks.
Currently I am masuring between Battery minus and the alternator + 4.8 Volts regardless whether the engine is on or off. All connections are tested and tight.

Any ideas?

 

[byron]

I don't know where you keep the boat but if it is within reasonable travelling distance of Wallingford in Oxfordshire call in Haynes Brothers, they really are the kiddies on anything auto-electrical - their speciality. They have a website but I don't have their address I'm afraid.

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[philip_stevens]

a Yell.com search found this:

Haynes Bros (Wallingford) Ltd
Station Rd Ind Est,Station Rd
Wallingford Oxfordshire OX10 0HY
Business Type: GARAGE SERVICES

Tel: 01491 836097

hope this is of help to you

regards,
Philip

 

[byron]

AND.... here's their web address
www.haynesbros.co.uk/

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[jfkal]

Thanks guys but I am in Singapore. A bit too far

Brgds

Joerg

 

[david_bagshaw]

You say eats alternators,

which component fails, the regulator, or the main .diodes.

When it is working what rate does it charge at , & for howlong, does it ever cut back what is the out put voltage.

Is there plenty of cool air round it while working, just incase you are frying them.

Do you have some other charger / float system & is that putting out the correct smooth voltage, incase that is frying it.

how old is the splitting diode, as their propities change after a few years, try the next alternator through a changeover switch instead.(had this personally, it was ok when measured with a low charge, but as the current increased it went belly up)

What is zap stop, may be that is the problem.

Hope that helps

David
www.yachtman.co.uk

 

[jfkal]

David,

thanks for your thoughts. Hard to say what fails. The dealers here just claim it is beyond repair. Air is enough it charges at 35 A and then cuts back slowly. I have got a solar panel and a sterling 220 V charger. The solar (40 W) connects to the stud at the splitting diodes. The diodes are brand new. The Sterling goes directly to the battery "behind" the splitting diode so no harm should have been done here?!

Zap Stop is a Zener diode across the terminals of the alternator and supposed to prevent an "open" alternator to run off in voltage and kill itself.

Brgds

Joerg

 

[hugh_nightingale]

From your posting I am not quite sure of your exact set up.
It seems you have more than one battery and a set of splitting diodes (something I would always recommend - see previous postings, I don't believe in connecting batteries in parallel regardless of what is shown, even in PBO).
As a first step I would disconnect all but the engine starting battery and work from there.

With engine off and switches off you should see the battery 12V at the battery terminals but not at the alternator (if you have the diodes connected correctly).

Make sure you have no loads connected to eliminate shorts in the boat.

What I am saying is go back to the simplest system you can organise and try that.

Send more information.

 

[oldjohnnyb]

don\'t use blocking diodes with your alternator

Since your alternator has only three connections, the regulator is controlling voltage internally. Using blocking diodes introduces a voltage loss of about one volt, hence your batteries will not ever get a proper charge.
Using a battery relay energized from the ignition warning light would overcome this problem.
The more expensive solution would be to used an adverc regulator, a system which is commented on many times in this forum. Use the search feature on the forum site to find out more.
The adverc system converts your alternator into a "battery sensing set up"
It is possible that the blocking diodes are allowing the output at the alternator terminals to rise to a higher level than it would if a battery were directly connected it is just possible that your zapper unit is overloading the alternator. Try leaving off the zapper device.
I am aware that lucas used to supply a large oil filled Capacitor to hold down the voltage of open circuited alternators but using a zener doide is new to me.

 

[Juggler7823]

You have mentioned a 'Sterling' for the first time. Is it a standard pulley, your not spinning the alternator too fast? You must ensure that the alternator does not get too HOT, Singapore can have temps over 35 deg C. I agree with a previous poster - revert back temporarily to as simple a system as possible. Remove the splitter diode, Sterling booster, and extra battery. See how long the alternator lasts before adding extras.

Roy

 

[Stemar]

I recently had a van alternator die on me - still under guarantee. The chap in the shop took one look at the terminals, which were slightly burnt and said that the failure was due to a poor connection between the alternator and its plug. He did exchange the altenator, but warned me that he wouldn't do it twice. A new plug(crimp - on, but could just as easily have been soldered) cost about £3.

The clamp wasn't loose, but apparantly tightness has nothing to do with it. It might also have been those crimped connections that were the problem.

 

[charles_reed]

Sounds like the diodes are back to front

Most probably that or an inefficient earth return.

Auto alternators don't last long in a marine environment (4-5 seasons).

 

[david_bagshaw]

To get a conclusive way forward you realy need to know the type of failure, after all you are parting with the cash!

How recent was the last failure in terms of years & engine hours.

I dont personaly agree that automotive alternators only last 4-5 years, as on our last boat, 1970- 1989 we had one alternator failure, & that was due to operator error, (mine, forgot to switch on circuit breakers) & a few problems at first due to wrong sized wires. The boat had 2 standard alternators such as fitted to a car or small truck at the time.

Open circuit usually kills the regulator not the main diodes.

Incidently when your alt dies is that there is no charge current, or the lamp glows or what.

David
www.yachtman.co.uk

 

[jollyjacktar]

Have I missed something?

I thought that the connections on an alternator were an earth through the body to the engine block, a +, [-, to the battery [the earthed connection to the engine] and a FIELD coil wire [another +] to ignition switch to provide power for the electromagnet field coils when the motor is running and thus enabling charging to occur. Oh yes, and the charge light circuit is the other connection. You seem to be missing one lead? or have you connected the wrong leads. Make sure that your boat is negatively earthed and you have not reversed your polarity of the connectors.

 

[Guest]

Having read this thread I'm afraid I don't have any offers of help but an interested in the idea of using truck alternators. given the price difference between auto ond marine alternators the marine ones, if the auto ones last 5 years the marine ones would have to last about 30year to even come close to the same cost efficency! So are the marine ones really justified (I need about 50-60A @ 24v) and has anyone sucessfully used auto units, preferably with three stage regulators.

Roly, Voya Con Dios, Glasson, Lancaster

 

[jfkal]

Re: Have I missed something?

No, there is no field wire since the alternator is internally regulated.

 

[jfkal]

Re: don\'t use blocking diodes with your alternator

The zener conducts at higher voltages and keeps the voltage from running away. They cannot overload since they come with a fuse which did not blow as of yet. Just the alternator dies quitely. It did that with the old splitting diodes and the new and with or without the Zap Stopper.

 

[david_bagshaw]

Re: don\'t use blocking diodes with your alternator

you say dies quietly,


you mean no charge output at all, does the charge light glow , go out, not go out??

any sign of impending doom ?

Is this a 24 v set up & if so do you have

1 any 12 v equipment on board

2 any 24 to 12 v droppers.



David
www.yachtman.co.uk

 

[oldjohnnyb]

What about the 4.8volts?

OK jfkal, so it's most likely we're eliminated the zap stop as the cause of your problem.
What about the blocking diodes. It's possible the alternator you have doesn't like feeding the battery through the diodes. (it would depend on how the regulator is fed)
Not withstanding the voltage your loosing, you should try getting rid of the blocking diodes.
In your first posting you said you are getting +4.8 volts between the alternator and battery earth with the the engine off or on! This is odd to say the least and would suggest a lost or poor connection on the earth wiring.
Check the readings again.
I would mention that readings taken with digital voltmeters can cause confusion because they have an internal resistance measured in megohms. As a result they can register reading from leakage through dioded and stray ac voltages. To be sure I would suggest you connect a small 12volt lamp in parallel with the meter or use a moving coil meter.
John

 

[jfkal]

Re: don\'t use blocking diodes with your alternator

Typically is all works for a while 30 A of charging current. Next time I go out no charge at all. The charging control light comes on dimmly and gets brighter with higher revs. The system is pure 12V system. Batteries are new, splitting diodes are new.