Dual alternator and oversize alternator success (or failure) stories

[RaymondR]

Originally Posted by Emmalina

Funny thing is I want to remove my genset 8kw as all it was really used for was AC and a big fridge compressor. Now have 12v compressors and don't use AC (shock horror for our US friends) so if I take it out can put more batteries and a small petrol frame honda driving a couple of alternators as back up !

I am going this route with an electric start 5hp Honda. 1/4 the cost of a quality diesel.

I am also going to belt drive the high pressure pump for my water maker off the same engine. I might also run an auto aircon refrigeration compressor from it.

I tend to the opinion that once you install a fairly high wattage inverter you are better off with a high capacity DC voltage generator to charge house batteries and it can be used for cranking assist of the main engine if required.

I am working through the safety issues at the moment and believe they can be overcome. After all we already have gas piped into our stoves and most of us carry petrol for our outboards.

On my last boat I had the Honda mounted on the deck in an alloy box and belt drove the alternator and compressor down through the deck to where they were installed inside the boat.

[Dockhead]

Originally Posted by Rumpi

. .. . On the other hand the whole setup is only viable if the diesel is small enough to ensure the PM generator loads it up properly and the batteries can accept the load. If the boat is big enough to have a motor over 40HP you either need a monster battery bank or a chemistry capable of beeing charged over 1C. Otherwise getting a small generator is the better option. After all how many boats need a generator over 20kW to charge their batteries?

A big advantage of using lithium for such an installation is that you can load up the engine better, if your alternator is big enough, and you'll have much shorter run times.


And running the main engine just to generate power may be reduced since you can capture power produced incidentally to propulsion, much more efficiently.


But I think you need to be careful not to overload the engine, as well as underload it -- when you start talking big alternators, you can't always assume that there is enough room between what the propeller needs and what the engine can produce at a given RPM, especially if you have a variable pitch prop.

[Albro359]

We have a 175A 24V Leece Neville alternator on our 4 cylinder Yanmar 4JH3HTE on the opposite side of the standard 12v alternator that charges the start battery.
We have a 660Ah 24v AGM bank on a 53' boat. I couldn't imagine a 1200Ah bank on a 25' boat....you're kidding, surely
What do you have on board that you need that much power?....IF you discharge it 25% that's 300Ah to put back.....we rarely exceed 100Ah overnight at anchor and when sailing across oceans it's about 160Ah / day and we have autopilot, electric winches, furlers, chart plotters, laptop etc
We have a 7.5kVA genset that runs a Victron 100A and a Promariner 30A charger as well as the watermaker, washing machine, hot water cylinder, microwave, dishwasher, dive compressor and 3 air conditioners - not all at once.....and 600W of solar panels......and it all works very well.

[john61ct]

Originally Posted by Dockhead

A big advantage of using lithium for such an installation is that you can load up the engine better, if your alternator is big enough, and you'll have much shorter run times.


And running the main engine just to generate power may be reduced since you can capture power produced incidentally to propulsion, much more efficiently.


But I think you need to be careful not to overload the engine, as well as underload it -- when you start talking big alternators, you can't always assume that there is enough room between what the propeller needs and what the engine can produce at a given RPM, especially if you have a variable pitch prop.

Should be no problem if you have an adjustable VR to adjust / derate the amps. A 300A alt only putting out 20A does not have a much greater load (about a horse?) compared to an 80A alt putting out 20A.

[john61ct]

Originally Posted by Albro359

We have a 175A 24V Leece Neville alternator on our 4 cylinder Yanmar 4JH3HTE on the opposite side of the standard 12v alternator that charges the start battery.
We have a 660Ah 24v AGM bank on a 53' boat. I couldn't imagine a 1200Ah bank on a 25' boat....you're kidding, surely
What do you have on board that you need that much power?....IF you discharge it 25% that's 300Ah to put back.....we rarely exceed 100Ah overnight at anchor and when sailing across oceans it's about 160Ah / day and we have autopilot, electric winches, furlers, chart plotters, laptop etc
We have a 7.5kVA genset that runs a Victron 100A and a Promariner 30A charger as well as the watermaker, washing machine, hot water cylinder, microwave, dishwasher, dive compressor and 3 air conditioners - not all at once.....and 600W of solar panels......and it all works very well.

1200AH in LFP is about the same weight / space as your bank, but provides over triple the usable AH capacity.

Eliminate the AC gennie and you need a bigger bank, if you avoid buying one, will more than pay for the LFP transition.

[Jammer]

Originally Posted by Albro359

I couldn't imagine a 1200Ah bank on a 25' boat....you're kidding, surely

I'm thinking ahead to my next boat. I like my 25' boat but it will never be acceptable for overnight trips unless I want to cruise by myself .

What do you have on board that you need that much power?......We have a 7.5kVA genset [...].

I'm contemplating an electric galley and no genset.

[a64pilot]

Originally Posted by john61ct

Are there any "PM generator 101" resources, plain-Joe installed commercial products in the 2 to say 6kW range, not mor expensive than the regular sort?

Or are these just science project ideas at the low end?

What is the main practical advantage over high-end but standard type alternators in generating high amp DC?

Alternators of course are AC not DC and AC is rectified to pulsating DC.
Not usually an issue though as it’s buffered if you will by a monster capacitor, the battery bank.

From a cost and reliability perspective, I think it would be hard to beat a Military high amp alternator.
On my engine, the only place such a monster could go is above the engine, something that for some reason I have not seen done.

What has me curious about the PM generator pictured is what are all those big leads for?

[Jammer]

Originally Posted by a64pilot

What has me curious about the PM generator pictured is what are all those big leads for?

You mean the red Electrodyne in the post upthread? I don't believe they are PM. I believe they have some variation of the usual brushless arrangement where there's a diode on the rotor. Their literature says there are no moving windings, but it also says things like "only one moving part" that are obviously hubris (there has to be a bearing at each end of the shaft, for example).


Anyway, the big leads are the stator connections leading to a full-wave rectifier offboard somewhere. Usually the rectifier (aka the diodes) is on the back of the stator, inside the housing. Moving it to an outboard location is mainly a strategy for thermal management, since both the windings and the rectifier produce a good deal of heat.


Since the voltage drop across a rectifier diode is more or less the same regardless whether the system voltage is 12v or 24v, the amount of heat generated by the rectifier is higher for 12v systems of the same output wattage, due to the higher current. Across a full-wave bridge the diode drop is 1.4 volts regardless of current, so for a 200 amp alternator, for example, there are 280 watts being dissipated in the rectifier, not an insignificant amount, and on par with the resistive loss in the windings and magnetic losses in the core.

[a64pilot]

Yes, it was the red alternator.
I know about external rectification, just 6 large leads confuses me.
If it’s what I’m thinking, I don’t understand why it’s not one large one.

[Jammer]

Originally Posted by a64pilot

Yes, it was the red alternator.
I know about external rectification, just 6 large leads confuses me.
If it’s what I’m thinking, I don’t understand why it’s not one large one.

Twelve pole stator, six phases in a delta configuration? That's how many of the high amp alternators are set up.

[a64pilot]

Originally Posted by Jammer

Twelve pole stator, six phases in a delta configuration? That's how many of the high amp alternators are set up.

My assumption as well, it’s why have them independent I guess that I don’t understand.
It would seem 6 wires, 6 diode banks etc is more complex and expensive than one big one?
There is obviously more to it.

[Jammer]

Originally Posted by a64pilot

My assumption as well, it’s why have them independent I guess that I don’t understand.
It would seem 6 wires, 6 diode banks etc is more complex and expensive than one big one?
There is obviously more to it.

Ah.


The different poles aren't in phase. I've attached an image showing the phase relationship for a 3 phase system. These aren't unusual for stock alternators -- I believe that the Delco AD-244 and CS-133 alternators that have been built by the millions are 6 pole, 3 phase machines.


In the diagram, the vertical axis is voltage (from -1.0 to 1.0; multiply by 16 or so for what you would see in a typical 12v system), and the horzontal axis can either be understood as time or as the rotational angle of the rotor.


As you can see from the diagram, the voltage peaks for each phase pair occur at different times. Each color in the diagram would show the voltage developed across one two-pole winding. The windings are connected in either star or delta, so that only three wires exit the alternator.


There's an article here that has a schematic of a full-wave rectifier, which is essentially the same as what most of the Delco 6-pole alternators use: https://electronicscoach.com/3-phase-rectifier.html


Now, for a twelve pole alternator, there are six phases, just think of the peaks of the 3 extra phases as each sitting half way between the voltage peaks of the 3 phases in the graph. Result is you need six wires because now you have peaks at six different times, and 12 diodes.

[Rumpi]

a64pilot you are confused because what you are seeing is actually not one but two brushless alternators siamesed inside the same case.
Since rectification is external you see 6 wires, 3 for each alternator, leading to big individual external diodes with computer fans on their respective radiators. They also have two field wires driving the two slave alternators, and you need two regulators.

Jammer is correct about the polyphase alternators, but as far as I know this units are not like that, they are just siamesed.

The problem with all of this big alternators is weight. Their rating is continuous duty not peak and as far as I know the E250-24 weighs something like 90-110lb. You can ask yourself at the source, they are in business. Electrodyne | Brushless Automotive Alternators

[jreyn1944]

In 2014 I installed commercial truck heavy duty Delco Remy 24SI 12 volt 160 A alternators on our twin Yanmar 4JH4 engines. The big advantage of a commercial truck heavy duty alternator is cost. I paid $150 each, for two installed plus a spare.


The installation required fabrication of a J-180 mount and idler pulley mounting plate, serpentine belt installation, and modification of the alternators to work with an external regulators. Balmar MC 614 regulators with the Centerfielder II were also installed.


The wiring and battery disconnect switches were upgraded to handle the increased current. 200 A fuses were also installed between the alternator output and battery bank.



The alternators have performed well over the last four years, accumulating over 2,000 hours of trouble-free operation.


I fabricated my own parts. I believe Mark Grasser sells the kit needed to install these alternators.

[Just Add Jimmy]

Just posting my brand new dual alternator set up on a Kubota D-1005. I custom made the crankshaft pulley adapter for twin 1/2 V belts. Call Brian from JK Pulley's. You can find them online. One groove for the Balmar alternator and the other turns the Sanden compressor for engine driven
air conditioning. Also designed the alternator mounting. If you just want to add another small alternator with a 3/8 belt Kubota does make the pulley adapter which just bolts on. Its a very hard to find part but I have one for sale. 75.00 It should fit most 3cyl Kubota based engines such as Nanni, Universal 25, Beta Marine. Message if you need additional info.


Jimmy

O'day 34, Jaimaican Me Happy