Dual alternator and oversize alternator success (or failure) stories

[john61ct]

Originally Posted by Dockhead

I'm not even sure a clutch doesn't make sense, for a real monster alternator on a PTO.

If you mean to save wear and tear on the PTO stuff, maybe, but I'd only think so if

the time ratio between motor running and alt needed is very high

I hope charging my LFP bank will only take 3-4 hours total a week, but then I personally don't intend to motor much.

Those "monsters" like military Hummer 400+A units have a very robust duty cycle

Or do you think they'd even have a significant drag when producing zero amps?

[Dockhead]

Originally Posted by john61ct

If you mean to save wear and tear on the PTO stuff, maybe, but I'd only think so if

the time ratio between motor running and alt needed is very high

I hope charging my LFP bank will only take 3-4 hours total a week, but then I personally don't intend to motor much.

Those "monsters" like military Hummer 400+A units have a very robust duty cycle

Or do you think they'd even have a significant drag when producing zero amps?

I think the whole PTO mechanism will be eating power when the alternator is not running, and wearing out to boot.


I am actually considering something like this for my next boat, so it's not just idle curiosity.


A monster alternator on PTO for large scale power production when the main is NOT being used for propulsion. Geared to produce maximum power at a low enough RPM to really load up the engine. And then a normal school bus alternator in the normal place, to support loads when you're motoring and do some lower-key charging. I think about redundancy here too because I think about doing away with the generator.



I'm just toying with this idea; the boat is for extreme remote sailing so the design brief calls for extreme robustness of the power system, so I might not be able to get away from having a generator, but it's still an intriguing idea.

[sail4evr]

Originally Posted by CarlF

I've had a large frame Balmar 95 Series (210 amp) attached to my Yanmar for four years using a kit sold by Balmar. I figured Balmar would have to stand behind it.

The thing is very beefy and has been trouble free.

AltMount Pulley Kit: 48-YDA-4JH-B

Carl, Was this a replacement for the original? Did you do the install yourself? Was it pretty straightforward? About how long did it take you to install it? How often do you have to replace your belt?
thanks, Joe

[john61ct]

Originally Posted by Dockhead

A monster alternator on PTO for large scale power production when the main is NOT being used for propulsion. Geared to produce maximum power at a low enough RPM to really load up the engine. And then a normal school bus alternator in the normal place, to support loads when you're motoring and do some lower-key charging. I think about redundancy here too because I think about doing away with the generator.

Yep along my lines too, in my case avoiding ever putting an AC genset in.

Possibly refrigeration compressor for holding plates, maybe direct watermaking too, along the Aquamarine lines.

Would the PTO idea really have such advantages over belt & pulleys? Serpentine / multi-vee scales pretty high, then there's toothed drive belts. . .

In my case engine redundancy would be only for propulsion, with an outboard, usually used for the dinghy.

[Dockhead]

Originally Posted by john61ct

Yep along my lines too, in my case avoiding ever putting an AC genset in.

Possibly refrigeration compressor for holding plates, maybe direct watermaking too, along the Aquamarine lines.

Would the PTO idea really have such advantages over belt & pulleys? Serpentine / multi-vee scales pretty high, then there's toothed drive belts. . .

In my case engine redundancy would be only for propulsion, with an outboard, usually used for the dinghy.

I have multi-vee now, and it is marginal even for producing only 2.5kW, and I worry about the side loads. I don't know about toothed and serpentine belts -- probably these are much better. But I was thinking of the PTO in order to get the monster alternator off the main engine for purposes of cooling and service access, and to leave space for a normal school bus alternator.



Still just a pipe dream, so not a fully developed vision.




If I were you -- I wouldn't bother with mechanically driven fridge compressors or watermakers. That's a lot of complication in the engine room. If you have a real heavy duty alternator, it's simple to drive this stuff electrically.


I have very, very positive experience over 9 years with a Leece Neville 110 amp * 24v school bus unit -- I even drive the washer/dryer via an inverter with it. When the main engine is running, it's as if I'm on shore power. It will produce 2.5kW 24/7/365 without breaking a sweat -- only problem is being careful to keep the belts adjusted.



I've said it before but it's worth repeating -- this kind of gear is really what you want on board -- cheap, dead simple, crude, beefy, easy to repair yourself or in any 3rd world auto electric shop, easy to keep a complete spare unit. Kind of the Kalashnikov of power production.



I love my heavy duty AC generator, I really love it, but if it broke in a remote place -- God forbid -- I'd be screwed. If you want for your power to be totally reliable, if you want to be totally certain that nothing can take it off line, so that you can run mission-critical gear off it in remote places, then an AC generator is not the right solution unless you are trained and equipped to repair anything which can go wrong with it, and keep £5000 worth of spares on board.



A school bus alternator you can fix with a hammer and duct tape (practically). And that's actually an argument for a stock school bus alternator over an exotic Ecotech etc. ultra heavy duty unit, too, if you were forced to choose. I would not want to give up the former, even if I had a way to use the latter.

[skenn_ie]

One alternator, charging at 25% Ah. A good way to boil your batteries

[skenn_ie]

Originally Posted by john61ct

Or do you think they'd even have a significant drag when producing zero amps?

Drag is belt, bearing, and air. All minimal. With no load, belt friction is reduced, but still there. V belts are usually about 90% efficient when driving a load. PolyV, something like 95%. Flat belts can be as high as 98%.

[john61ct]

25% of what?

And a little boiling's very healthy. . .

Obviously as a major power source into an expensive deep cycling bank, a fully adjustable multi-stage VR like MC-612 is called for.

[skenn_ie]

Originally Posted by Dockhead

I'm just toying with this idea; the boat is for extreme remote sailing so the design brief calls for extreme robustness of the power system, so I might not be able to get away from having a generator, but it's still an intriguing idea.

I suggest a PMA with enough output to run all ship's systems, with a 2nd to charge batteries. You could use a higher power PMA and rig a resistive load to prevent overcharging.

[skenn_ie]

Originally Posted by john61ct

25% of what?

And a little boiling's very healthy. . .

Obviously as a major power source into an expensive deep cycling bank, a fully adjustable multi-stage VR like MC-612 is called for.

25% of battery Ah rating. I presume that you have seen batteries that have been overheated ? Bulging case, distorted plates, sometimes to the extent that they touch and short-circuit.

[john61ct]

Current rate doesn't matter, in fact .25C is rather low for AGM.

I've never used a charge source that would overcharge - meaning fail to properly regulate voltage - to that extent.

And all my current ones have temp sensors for both overtemp protection and automatic voltage adjustment.

[Jammer]

Originally Posted by Dockhead

I'm not even sure a clutch doesn't make sense, for a real monster alternator on a PTO.

I have operated and repaired some extremely large agricultural equipment.


Some combine harvesters I have worked on are equipped with 200 hp diesel engines and deliver all of their power through V-belt drives.


All 200 hp of it. The belts require periodic replacement but last over 1000 hours, typically.


There are electromagnetic clutches for the separator (which uses most of the power) and the unloading auger. Hydraulics run all the time, and provide power for controls, steering, and the drive wheels. The ones that are air conditioned have an engine-driven compressor and a 2nd alternator for the fans.


In industrial applications V-belts are widely used across a broad range of power levels from fractional up to 100s of horsepower.


The point being that V-belts are suitable up to far larger power levels than are likely to be encountered in the electrical system on a yacht. At higher horsepower, larger pulleys are generally used, with larger belts. It is the very small size of the typical alternator pulley that limits the power transfer capability in typical automotive/marine alternator installations.