Alternator dummy here needs help!

[Bleemus]

I currently have an 150 amp alternator with a v-belt and it eats belts. We see a very rare need for using engine to charge batteries due to solar, wind and our usage habits.

Instead of upgrading to a serpentine belt we are considering downgrading to a lower amp alternator that will be easier on the belts. Current alternator has AC output of 6-8 volts off a terminal marked P which runs our tachometer but all of the alternators I am seeing have nothing more than DC out to batteries.

What should I be searching for to find alternators that have the needed AC output for our tachometer?

Thanks.

[SailRedemption]

The recommended alt amperage for a single v belt is around 90-100. I would suggest you get a Balmar mc-614 alternator regulator and use the "belt manager" to derate the 150a to around 80-90. Your alternator will run cooler, and will last longer as well since it's not working as hard as it's rated for. The Balmar is a good investment and will take care of your batteries much better than without a external regulator. No sense and getting rid of your current alternator. If your needs change down the road and you want to charge more via engine you can always make the decision to upgrade to a serpentine belt.

Also, check out marinehowto.com for the article on the Balmar regulator.

[smac999]

Most Alts will have a tap for tachs.

But as above. Consider external reg turned down instead. . it will charge way better too.

You'll have to remove the alt and get a shop to modify for external reg. assuming it's currently internal.

[GordMay]

Originally Posted by smac999

Most Alts will have a tap for tachs ...

The alternator may have one or more AC stator tap terminals (may be labeled R, W, S, T, or AC) that are used for tachometer input.

[S/V Alchemy]

Good advice here. Another option (or an additional option) is to change your PTO to accept grooved "serpentine" belts, which are preferable in my view to V-belts in terms of wear, efficiency and longer life.

[01kiwijohn]

Keth, you don't say which engine you have.
I faced a similar choice, and have a Yanmar 3GM. Here's what worked for me:
A 3/8 inch section belt is good for a reliable 80 HP. I didn't want to convert to serpentine belt either, so used this to determine alternator output.
Alternators with a Yanmar mount were not ubiquitous but eventually worked with a company called BD Electrical (https://www.dbelectrical.com/product...6ly-kbw20.html), who subsequently released an 80 Amp version with Yanmar mount lugs. It also has the electric tach connection.
Since I also increased house battery bank to 400+ AH, I also decided on an external (Sterling) regulator, which, over the past 8 years of summer liveaboard use, has performed very well.
Subsequently, I had to increase the wire gauge, of the alternator output to the starter solenoid terminal. (ask me how I figured that out).
My annual PM schedule specifies replacing belt every second year., but they've not had any noticeable excess wear so far.
Hope this helps with your installation. If you have questions, please let me know.

[oleman]

The simple solution that has been used for the past 100 years is multiple V belts with correct matching and tension. We run a 200A alternator using 2 EA 3/8" standard belts on an old Detroit Diesel 2 stroke, belt life basically has been measured in years. Actually the normal V's last longer than a loaded idler on a multi-grove belt.

[Lepke]

Originally Posted by oleman

The simple solution that has been used for the past 100 years is multiple V belts with correct matching and tension. We run a 200A alternator using 2 EA 3/8" standard belts on an old Detroit Diesel 2 stroke, belt life basically has been measured in years. Actually the normal V's last longer than a loaded idler on a multi-grove belt.

Me too. Twin Detroits with dual V belts will handle 200 amps maybe more. My current belts are about a decade old. Dual belt alt pulleys are available online from many alt parts places. Dual engine pulley should be available from your engine mfg or better marine stores.

[Bleemus]

I have a Westerbeke 55a. I think the mounts for the alternator were modified by a welder. Next time I am down there I will see about adding a second belt. If that looks daunting I will likely go with downsizing the alternator and using the external Sterling regulator I have that can handle a Max of 130amps. Thanks gang!

[CapnBazza]

Mine ate belts until I tightened things more than I thought I should. Touch wood but it’s been a year since I last renewed one.

[a64pilot]

Yes, instead of buying a new alt, put a good adjustable regulator in it, turned down to 60 amps or so it will always make 60 amps no matter what, and will probably live longer than you do.
I’m convinced that alternator life has a lot to do with how hot they are run, and a slipping belt will overheat the alternator shaft and bearings as the slipping belt adds a lot of friction heating.

[Maine Sail]

Originally Posted by Bleemus

I have a Westerbeke 55a. I think the mounts for the alternator were modified by a welder. Next time I am down there I will see about adding a second belt. If that looks daunting I will likely go with downsizing the alternator and using the external Sterling regulator I have that can handle a Max of 130amps. Thanks gang!

The Sterling ProRegD (an actual external voltage regulator) can handle an alt upward of 200A but offers no way to "de-rate" / reduce output amperage of your alternator.

If you are talking about a Sterling Alternator to Battery charger, such as the AB12130, then I would advise keeping your existing alt, it is well built, and derating it using Belt Load Manager in a Balmar ARS-5 or MC-614 regulator and selling the AB12130...

Why? Because the AB12130 also has no way to limit the output of an alternator so this means buying an 80A alternator and then taxing it until it fails. You will have better long term reliability running a 150A alt at 80A or so (via belt load manager) than you will trying to run an 80A alt at 80A.

[Bleemus]

Is the Balmar ARS 5 a direct replacement for the Amptech Stealth?

http://www.mpowermfg.com/stealth.html

[Bleemus]

Current config. Doesn't look like a serpentine belt is in my future and I am unable to find a fresh water pump pulley that will accommodate two belts. Scratching my head.

[bcboomer]

If there is a machine shop nearby they could make a double belt pulley for your pump. Would be cheaper and easier than a serpentine conversion.