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Alternator/tachometer problem... Related?

2K views 5 replies 3 participants last post by  deverett 
#1 ·
Westerbeke 27 w/stock 50 amp alternator ran fine during preseason commissioning. We launched this weekend and the tachometer was inop upon startup... I could smell a very faint, but distinctive electrical, hot acrid smell. I then noticed that the charging voltage climbed to 14.9 volts and held steady. Either I was imagining things, or whatever was hot ended up burning up, because the smell went away and hasn't come back.

Did I suffer one failure or 2? I believe that the tach takes input from the alternator, so it seemed too much to be a coincidence, but I can't convince myself what piece it would be. Voltage regulator? (Internal to alternator) would that fail the tach?

I can't swear to it, but I'm pretty sure that my normal charging voltage is usually 14.4, which is spec for this alternator. I know it has changed, because my Batterylink ACR combiner is now indicating overvoltage and not combining. I can adjust the setting to make it happy, but I want to confirm what has failed before doing that.

Other details... House bank is 6 Trojan 6volt wet cells (650ish ah), starting battery a traditional cranking bat. (I know, I know... Not a great charging set up for such a bank, but load is minimal, and it has worked well for many years)

Thanks for your thoughts!
 
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#2 ·
Deverett,

From what I can tell from your description, I believe you have successfully diagnosed the issue: your electric tachs are fed from your alternator.

If the alternator voltage regulator is indeed internal, there is not much you can do but convert the alternator [if that models can be...] to use an external regular, or replace the alternator to one with external regulation. [Ask an alternator shop or the manufacturer about the feasibility of converting to an external regulator.] If it can be converted, or if you buy a new alternator, then you can acquire an external regulator to go with. [e.g., Balmar 614 or the like...]

That will not only give you better control over the charging regimen, but your tach(s) will also work again.

In hopes you get things back to normal soon...

Cheers!

Bill

PS: The bulk charge voltage [@75°F] for your Trojan T105s paralleled into a 12VDC bank is 14.8 VDC; Acceptance is 14.4, and float is 13.2 [I use the Trojan T-105s configured this way as well...]
 
#3 ·
You need to get the alt off and tested. The AC tap/stator tap drives the tach and unless the field is being driven the tach will not see the stator tap signal..

PS: The bulk charge voltage [@75°F] for your Trojan T105s paralleled into a 12VDC bank is 14.8 VDC; Acceptance is 14.4, and float is 13.2 [I use the Trojan T-105s configured this way as well...]
Absorption is 14.8V (Trojan refers to this as the "daily charge"), float is 13.2V (though in a PSOC situation they generally do better at 13.6V+/-).

There is no such thing as a bulk charge voltage (other than in marketing mumbo-jumbo) because bulk is constant current (voltage always rising) not constant voltage (voltage held steady).

 
#4 ·
Thanks for setting me straight, Main Sail.

Your clarification made me realize I have allowed myself to become brainwashed by the vendor literature.

In this case I was quoting bulk, absorption, and float [terms and voltages] from memory programming our Balmar 614 without thinking. Of course the danger in that is misremembering a value, and more importantly- as you point out- promulgating misused terms and concepts.

While Balmar insists we set a Bulk charge voltage set point, in reality one doesn't exist.

To add to the confusion the data sheet for T-105s has changed slightly from the version I downloaded 2 years ago. Trojan has changed the term Absorption [@ 14.8VDC] to Bulk [still @ 14.8VDC] I noticed they also increased both Float [from 13.2 to 13.5] and Equalize voltages. [from 15.5 to 16.2]

I guess I have some reprogramming to do... [My brain, the alternator regulator, and the AC battery charger...]

And another lesson earned: it pays to occasionally check vendor data and specs to watch for recommended changes.

Thank you for reminding me to not always accept, but instead interpret, then translate, the engineered [not engineering...] terms [mis]used by some vendors.

Cheers!

Bill
 
#5 ·
Bill,

This is very common throughout the industry where marketing teams create sell sheets and the engineers fail to catch the mistakes.

Compound that on-top of charger manufacturers who never speak to battery manufacturers and we, the end user, suffer.

Trojan has been revamping charge voltage suggestions now for a number of years. It was not too long ago that absorption was simply the old school 14.2V - 14.4V which is pretty much murder on deep cycle flooded batteries used in a PSOC application. Some of us in the industry were already there, at 14.7V to 14.8V, before Trojan even published it.....

On the good news front Trojan and others are finally paying attention to what actually works for PSOC use from the off-grid/renewable energy market. This is a much larger market and they can't just ignore the issues like they did previously with marine off-grid/PSOC use. In a few weeks I get to go to this years renewable energy Trojan seminar and find out what they have changed this time...:wink
 
#6 ·
Thanks guys, I will pull it next week for a bench test... Would you expect the AC/tach output to fail as a result of a regulator failure?

Probably should research viable mid range upgrades for Westerbeke 27 alt... Thoughts?

Thanks again,

dev
 
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