Flakey Tach

[jviss]

I have an electric tach-hour meter, standard Westerbeke panel. It's flakey - doesn't always register the speed, but works when motoring for a while. I suspected that I had a slipping belt, as it's a standard V-belt driving a 124 Amp Ample Power alternator. But, I don't see the current dropping out. I only rarely hear a squeal, when I have a low house bank and push it hard. I'm usually around 65 to 75 Amps during bulk with the engine running about 1500 RPM - though I can't be sure of the speed at times. There's significant belt dust.

Is this flakiness due to a slipping belt? Or, are there other known faults that produce these symptoms?

Thanks,

jv

 

[Cowpokee]

I too have an electronic tach that occasionally reads erratically. I attributed it to a poor connection somewhere. Haven't traced it down yet to confirm because I have become familiar enough with the boat now that I can tell the rpm's by listening to the engine.

 

[jssailem]

JV. There may be a couple of issues.
Tach Flakey behavior is likely do to the alternator being used as the signal for the tach. If the alternator regulator says 'Hey the batteries are full turn off.' Then the signal to the tach turns off. Suddenly the batteries are drained a bit due to a light or a radio being on and the regulator says 'Whoa... the batteries need me.' Your signal is turned back on and the tach says JV all is ok. I'm back. Carry on. To address this you have a couple of ways to go. One is to get a pickup for the tach from the shaft. Small magnets attached to the shaft or back of the engine shaft pulley and a pick up to record the rotation and send the signal to the tach. My friend @LeslieTroyer can give you the specifics. As a work around, maintain a DC drain ( ie. lights) so that the regulator never is told that the batteries are full.

Significant Belt Dust... Most likely the alternator and the engine pull are not aligned. You need to examine the alignment and modify the alternator with shims or bolts to get the pulley's in alignment.

Or you may just have an old belt and it is time for a change..

That's what I got and how I would attack the situation.

 

[jssailem]

Cowpoke. Listening to the engine and being able to say... Yep.. were cruising at 1850 RPMs, is a great gift. Works until your hearing starts to go... and you find your self saying 'Eh... what did you say?' frequently.

But is is nice to know that your boat is operating in sync with you.

 

[Cowpokee]

Cowpoke. Listening to the engine and being able to say... Yep.. were cruising at 1850 RPMs, is a great gift. Works until your hearing starts to go... and you find your self saying 'Eh... what did you say?' frequently.

But is is nice to know that your boat is operating in sync with you.

Thanks, but not so much as a gift but just decades of sitting next to running diesels for hours on end. Whether in heavy equipment, farm tractors, trucks, or boats, each engine has its own "sound". Anytime that "sound" changes, it is time to look into why.

 

[NYSail]

With that size Alt I would imagine your standard v belt in inadequate..... sure it spins but you are dusting the place. You did not say make of Alt, however if you go onto Main Sail's site he has some nice serpentine belt kits for sale! I love mine with my 150 amp alt... no dust, no worries and it looks cool too!

Good Luck
Greg

 

[jviss]

Hi Greg,

Thanks for the reply. I think I did mention the make of the alternator, it's an Ample Power. I think they are out of business.

I am aware of the serpentine belt kits, and I'm about to order one.

Glad you like yours! When I get mine I'm hoping for a 100A bulk charge.

 

[jssailem]

Anytime that "sound" changes, it is time to look into why.

That is the truth. Certainly on my boat it is happening. I'll be sitting there enjoying the sunshine gazing over the water and there will be a tone change or a half a cough and I am off my butt looking at the water flow, the temps, the fuel, and tach... What caused that? What are the symptoms... Often it is just a half cough. Nothing is evident. So I return to my seat, but now I am a bit wary....

 

[jssailem]

When I get mine I'm hoping for a 100A bulk charge.

Boy that would be nice. Hope you find Nirvana....

 

[jviss]

Boy that would be nice. Hope you find Nirvana....

Hey John, I routinely saw 90A on my C36 when I first started charging, but that particular alternator/regulator combo was weird, and couldn't keep it up 'til I hit accept voltage. I can see no reason this setup, 38HP diesel, 124A alternator, couldn't do it. I can bring the engine speed up enough to get 75A now, but beyond that the belt squeals. With a serpentine belt upgrade should work at 100A, no?

 

[jssailem]

I can bring the engine speed up enough to get 75A now, but beyond that the belt squeals

As one would expect it too. At some point, in your case when the alternator is trying to spin fast enough to generate 75A. the alternator magnetic fields, the bearings, the pulleys, the water pump all conspire to resist the belt moving faster to push the alternator faster to pump out more amps. Result belt squeal.

Note that typical regulated alternator performance is 50% or so of designed performance. So my 65amp OEM alternator could produce maybe 30 to 38 amps.

My new 105 alternator I suspect is chugging out in the 65 amp range. For my two 135 amp hour batteries that would be pretty good. It would at least allow me to charge the batteries in a couple of hours of runtime on the engine. I have yet to measure and tweak the Balmer regulator to see if I can maximize the system.

 

[jviss]

My new 105 alternator I suspect is chugging out in the 65 amp range. For my two 135 amp hour batteries that would be pretty good. It would at least allow me to charge the batteries in a couple of hours of runtime on the engine.

To really, fully charge a pair of 135AH batts, meaning accept voltage down to 2% of total AH capacity, so 2.7A, in your case, would likely take four hours, maybe more. The speed at which you bulk charge, the difference between 100 and 65A bulk, is almost negligible, compared to the time it takes to complete the acceptance phase.

 

[jssailem]

Yes I agree. It is one of the compromises associated with being out cruising and relying on the engine as the recharge power source. Not getting the batteries back up to 100% SOC unless you can motor for a long time. Fortunately there is an opportunity here when moving any distance without a breeze.

This compromise is one reason to install solar. A likely addition if I can get to the time when I can be gone longer than a couple of weeks at a time. Ah. Future plans.

 

[Maine Sail]

Hey John, I routinely saw 90A on my C36 when I first started charging, but that particular alternator/regulator combo was weird, and couldn't keep it up 'til I hit accept voltage. I can see no reason this setup, 38HP diesel, 124A alternator, couldn't do it. I can bring the engine speed up enough to get 75A now, but beyond that the belt squeals. With a serpentine belt upgrade should work at 100A, no?

That old single fan 10DN based alternator is really going to be pressing hard to do a 100A bulk-charge for very long. To maximize life it would be best to belt manager it down to about 85-90A if you're running a Balmar or Xantrex XAR regulator.. If your bulk times are short, less than 15-20 minutes or so, it should be able to do 100A...

 

[jviss]

That old single fan 10DN based alternator is really going to be pressing hard to do a 100A bulk-charge for very long. To maximize life it would be best to belt manager it down to about 85-90A if you're running a Balmar or Xantrex XAR regulator.. If your bulk times are short, less than 15-20 minutes or so, it should be able to do 100A...

Thanks. Is that what I have, a 10DN alternator, with the Ample Power 124A unit?

 

[Maine Sail]

Thanks. Is that what I have, a 10DN alternator, with the Ample Power 124A unit?

No you have a 10DN "based" unit. Inside it is fully custom but shares some components such as spacers, brush holders etc.. The stator, rotor, rectifier etc. are all custom... Ample Power did not build their own alternator, they were custom built for them. We used to use the same builder but now do our own building in-house. The single fan 10DN frame only allows for so much cooling no matter what you do to the stator, rotor or internal rectifier.

 

[jviss]

Thanks. By the way, what do you think of the hairpin-wound stator alternators? Are they available in the 100 to 150A range?

 

[Maine Sail]

Thanks. By the way, what do you think of the hairpin-wound stator alternators? Are they available in the 100 to 150A range?

Balmar's latest technology, the Advanced Braided Technology, that's used in the new XT-170, is even better for long bulk duration charging. It is a hybrid wind that allows better for better cooling than the hairpin and still yields high output at low RPM.... They also don't need to pay Denso for a license to use the hairpin technology so the XT-170 not only runs cooler but costs about $100.00 less than the discontinued AT-165..

 

[jviss]

Wow, thanks. But that's still a lot of money for an alternator, at least for me.

My current setup is pretty good, I think, except for the belt, that I sincerely believe is slipping. That will be solved when my serpentine belt kit arrives Thursday (thanks!). At this time I can put a days worth of electricity use back into my twin Trojan SCS200's in about two hours of charging on the hook, and of course, about the same if motoring. The bulk phase isn't that long - I'll have to check my logs. It's that tail from about 11%C to 2%C that seems to take forever, and the belt won't make a difference there. I've found I can slow down the engine, manually servoing to the acceptance voltage or 14.8V, so I'm almost idling for the last 45 minutes or so. But, bulk will certainly go faster, and the tach will work with the belt upgrade kit. And no more belt dust.

When I decide to increase house bank capacity I'll look at that alternator seriously.