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Old 12-12-2010, 16:15   #1
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High-Powered Alternator V Pulley

Hey,

We need to upgrade our alternator to a 80-90amp from a 55amp unit. It is possible to buy a 'V pulley' with 3 'V's ?

I have heard an alternator over 60amps needs aditional V pullys, or bunkier pulley.

Where would you one buy a pulley with 3 'V's?

cheers

Mark
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Old 12-12-2010, 16:43   #2
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A regular belt will drive a 90 amp alternator. Use a good Gates or Dayco belt. No need to change the pulleys for a double belt.
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Old 12-12-2010, 16:47   #3
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You might want to read this thread from last week.....
Is a 100 amp Alternator Too Large ?
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Old 12-12-2010, 16:52   #4
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Cheers for the info!
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Old 12-12-2010, 16:55   #5
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Just a note you might have to upgrade your wiring.
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Old 14-12-2010, 16:23   #6
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i def will be upgrading wiring as the existing wiring looks a little thin. i shall go researching for awg required
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Old 14-12-2010, 17:33   #7
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Maybe this will help............

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Old 15-12-2010, 15:21   #8
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Maybe this will help ...
Here ➥ Wire Size Chart.1 - Read /w "Ohm's Law & You" Cruisers & Sailing Photo Gallery

And Here ➥ Wire Size Chart.2 - Read /w Wire Size Chart.1 & "Ohm's Law & You" Cruisers & Sailing Photo Gallery
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Old 15-12-2010, 18:08   #9
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Before making the change, consider this. Copper has a positive temperature coefficient which means the hotter it gets, the higher its resistance becomes.

An alternator that operates for extended time WITHOUT a fan blowing on it nor being WATER COOLED will quickly develop internal heat---- like HOT! And the hotter it gets, the higher the internal resistance becomes which makes the losses higher causing it to get HOTTER! THINK THERMAL RUNAWAY.

Further complicating the operation of an alternator at high currents without adequate cooling, is how the internal heating affects the rectifiers.

Think about it.

Foggy
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Old 15-12-2010, 23:52   #10
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Before making the change, consider this. Copper has a positive temperature coefficient which means the hotter it gets, the higher its resistance becomes.

An alternator that operates for extended time WITHOUT a fan blowing on it nor being WATER COOLED will quickly develop internal heat---- like HOT! And the hotter it gets, the higher the internal resistance becomes which makes the losses higher causing it to get HOTTER! THINK THERMAL RUNAWAY.

Further complicating the operation of an alternator at high currents without adequate cooling, is how the internal heating affects the rectifiers.

Think about it.

Foggy
Each alternator is designed to run fairly hot. That's why they have a fan blade and the case made from aluminum, and sometimes even heat-sink fins.


170 amp........

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Old 16-12-2010, 00:00   #11
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We need to upgrade our alternator to a 80-90amp from a 55amp unit. It is possible to buy a 'V pulley' with 3 'V's ?

I have heard an alternator over 60amps needs aditional V pullys, or bunkier pulley.

Where would you one buy a pulley with 3 'V's?
What is the belt width? Which alternator are you considering (e.g., presumably a hot-rated unit)? Which motor will be spinning the alternator? How are you planning to regulate the alternator?

In general a single 1/2" belt will pull a maximum 105 amp 12vDC alternator, you would bump up to dual belts if the alternator is more powerful than that.

As regards pulleys with multiple V's, yes, they can be custom-made to essentially anything you want. Be aware that the belt places off-axis loads on the engine crankshaft bearings (and usually the engine coolant pump), and you want to stay within load limits on those bearings.

You might also wish to compare the alternator's pulley diameter with the crankshaft pulley diameter - this will impact low-RPM alternator output.

- rob/beetle
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Old 16-12-2010, 18:47   #12
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Each alternator is designed to run fairly hot. That's why they have a fan blade and the case made from aluminum, and sometimes even heat-sink fins.


170 amp........

Can you back that up with constant high current operating specifications along with a life expectancy chart? Even the rectifiers have iffy chancie life expectancy when operated at high temperatures. Most commercial semiconductors have high temperature ratings of only 80C. Military temperature ratings are higher at 125C

Foggy
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Old 16-12-2010, 20:29   #13
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Can you back that up with constant high current operating specifications along with a life expectancy chart? Even the rectifiers have iffy chancie life expectancy when operated at high temperatures. Most commercial semiconductors have high temperature ratings of only 80C. Military temperature ratings are higher at 125C

Foggy
Out of the hundreds of alt's I've rebuilt, 20 to 300 amp, the few that were fried had a diode or two that had shorted or the stator had lost its insulation probably due to vibration.
An alt. that gets overloaded (dead or bad batteries) usually takes out the brushes or opens the diodes, slowing the charging process to nothing, eventually.
In my spares kit I carry brushes, bearings and a regulator. The rest I don't worry about.
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Old 17-12-2010, 09:21   #14
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Del--

You have hands on experience! My last post was not well thought out. For example, engineers can design and build alternators that will output large currents for sustained periods in harsh conditions. But they become very large, possibly water cooled, often impractical for most boats.

For general use, I still maintain that high output alternators operating on a hot engine in a bilge, in warm waters such as those in the southern climates are not something I would recommend. Can they work? Sure, but when operated with constant high current loads that result in high internal heat generation, they will be prone to short life.

Someone like yourself who has repair knowledge, understands alternators it might be a no brainer. But others who purchase and install a high current alternator may think they can charge batteries at 75 to 100+ amperes continuously in all kinds of environment, may find it a costly experiment. Just my thoughts--

Foggy
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Old 17-12-2010, 11:19   #15
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Foggy

I think what you're not seeing is; that the high output would only be for a short period depending on it's regulator. Some regulators are 3 stage. A 100 A alt. will bring a single gr. 27 battery up pretty darn fast! And as batteries come up the amperage draw drops and the alt. is working at a much lower rate (running cooler). BTW - No engine room is any hotter then Phoenix AZ, and alts seem to last there pretty good (where I use to rebuild them).

But if one had a battery(s) with a shorted cell or a power wire grounded, then the alt. would run as hard as the required draw. Automotive/marine alt's were not meant to run full time under load as industrial unites. Normally one does not want to take a battery below 75% anyway making a 100 A alt. fairly useless on a boat with only 2-3 standard automotive batteries. That's why I stated way early, and referring to a different thread "Unless you have a large battery bank (e.g. 1000 Ah) it would be over kill."

Hope that helps!
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