Alternator Size with LiFePo4

[Maine Sail]

Originally Posted by a64pilot

Maine Sail was selling the Mark Grasser J series alt at one heck of a price

That alt is the CMI-ED200-ER not one of Mark's. We build it here at Compass Marine along with a number of other models. We also sell Mark's alternators & Balmar too.

The costs savings on the CMI-ED200-ER come from no isolated ground, diesel use only (no USCG testing for gas engines) and from not keeping the internal regulator as a "back up". It's a pretty tough deal to beat in a large frame J180 that can be run at upwards of 255F.

[a64pilot]

Originally Posted by Maine Sail

That alt is the CMI-ED200-ER not one of Mark's. We build it here at Compass Marine along with a number of other models. We also sell Mark's alternators & Balmar too.

The costs savings on the CMI-ED200-ER come from no isolated ground, diesel use only (no USCG testing for gas engines) and from not keeping the internal regulator as a "back up". It's a pretty tough deal to beat in a large frame J180 that can be run at upwards of 255F.

Sorry, my mistake.
It is however a very good deal.

[rgleason]

Being large case, is there any chance it would fit a Yanmar 3YM30 dual foot?

I seem recall a reference to a J series installed on a 3ym30 awhile ago, but perhaps that was atypical.

PSS - found it with Bruce Scjwab and MG for 3ym3

Mark usually tries to get a higher ratio than 2.2. He does have a kit for his J180/250A on the 3YM30 with a 2.5 ratio. More info here:

https://www.bruceschwab.com/wp...ter...rice-Specs.pdf

This thread is getting interesting.

Based on MaineSail and Bruce Schwab's comment that lifepo4 really need a remote rectifier, so there must be a big improvement with that too, as well as lsrge frame.

[a64pilot]

I think you may find out that the Alt Maine Sail has will put out more power continuously then you may imagine, although I don’t know what that number is.
The problem with a small frame alt is not the power output, they have been very successfully hopped up, it’s the heat build up.
I think you’ll find that the difference in continuous power out out of Mark’s external diode J frame and Compass Marine is there, but it comes at a high price.

If I could just get one on my 4JHE.
I’d want it not so much for battery charging, but to run the Watermaker and charge batteries when we were motoring.

[tanglewood]

I think the question here is what's the continuous duty rating for any given alternator, as opposed to it's nameplate rating. That's a spec that is conspicuously absent from any datasheet that I've seen.


And heat build up happens in two places, the rectifier diodes, and the stator windings. Temp sensors like the Balmar sense the rectifers, not the stator. I instrumented the stator on a LN series 5000 "large frame" alternator, nameplate rating 190A @24V nominal. I regularly ran it at full output for hours at a time. The diodes never came anywhere close to the 100C trigger point for the Balmar regulator. But the stator, on the other hand, would reach 150C (300F). I spoke with LN about it, and you would expect the max allowed temp would be a specified number for every alternator, but no. After two escalations to engineering, the answer was that that stator temp was normal and acceptable. So my conclusion was that for that particular alternator, the nameplate rating was also the continuous duty rating. But I would not make that leap of faith on smaller units.

[john61ct]

The actual continuous duty output varies greatly according to the installation and ambient air temps.

Large-frame in general, and specialist units designed for deep cycling will be capable of outputting their rated capacity for longer periods in warmer conditions.

Small-frame stock alts, maybe guess half of rated.

There would need to be tight specs for such a rating, as with solar panels.

Deep cycle charging is such a tiny fraction of the market, can't see that happening.

[rgleason]

One alternative for regulators: Genasun AR2 Alternator Regulator

Another Alternative for Large 200ah capacity Alternators
https://www.electromaax.com/products...ators/genmaax/
and Serpentine Belts
https://www.electromaax.com/products...lley-upgrades/
Does anyone have good experience with these? I read some reports...

Bosch Long Haul Alternators
Bosch Hot Environment Alternators

Quote from A64 Pilot which makes lots of sense to me, maybe we should be testing ourselves and reporting in this forum? :

But what I am still suspicious of is, do you really get all that much more continuous power output from the larger say above 160 amp alternators, than say one rated at 100?

Continuous loads, I don't care what it can make for a few minutes, I want to know what can it sustain, like my Little Yanmar, 44 HP for one hour, 40 continuous.

I think a test run at continuous load under say 60C atmosphere would be interesting, or heck even if it was 25C, I think a test to see what the alternator stabilized temp at X load is, one 100 amp alternator and one much larger, just to see if there is any large difference in continuous output.

One of the main problems with small frame alternators is cooling (and to a lesser extent to large frame alternators). Grumble: Why don't Yanmar and other engine manufacturers design room for larger alternators?

A slightly involved cooling method for Alternators.

The engine is cooled with seawater transferred to system coolant. The alternator could be cooled with a small amount of seawater transferred to oil, coolant, or even direct to a fan coil. It could perhaps be direct heat transfer which would be more efficient but involving a more costly and complex alternator, or simply transfer via cool coils with fans.

[tanglewood]

Originally Posted by rgleason

The engine is cooled with seawater transferred to system coolant. The alternator could be cooled with a small amount of seawater transferred to oil, coolant, or even direct to a fan coil. It could perhaps be direct heat transfer which would be more efficient but involving a more costly and complex alternator, or simply transfer via cool coils with fans.

Or just raise the voltage. All these things add complexity, but higher voltage may be the least complex.


Or, just start your generator. It does a really, really good job generating power with low winding losses, and efficiency engine operation. It's your friend, not your enemy.

[rgleason]

Tanglewood, Thank you.


You suggest something I was thinking of, but I don't know enough about.
1. I have no generator. Boat is too small.
2. If I were to use a 24v alternator and 24v Lifepo batteries, how would I get the voltage back down to 12v for panel loads and the starter and engine instruments?
3. Never use shorepower. On a mooring, anchor or sailing. Currently have no Shore Charger. Might be able to find room for one with long runs.

Advantages of 24v Alt + Batteries
1. Smaller cables. How much smaller?
2. Less heat created at Alternator?? Is this correct?
3. Higher amperage can be maintained continuously?
4. Should 48vdc be considered?
5. System redundancy, simplicity and safety?

I would like to understand more about this atypical system and managing its complexity, what the pros and cons are.

[rgleason]

Perhaps use a 24VDC/ 12VDC transformer like the ETA-US ETG-SC unit with 600w power?


ETA-USA: DC/DC Power Supplies


Also found the Victron

Orion 24/12-25 25 amp
Orion 24/12-40 40 amp
https://www.victronenergy.com/dc-dc-...v-24v-48v-110v
DC/DC Converters

[john61ct]

Victron Orion series.

But better to just stick to 12V

[tanglewood]

Changing the whole system to 24V would help overall, but probably isn't practical. Lots of bigger boats are 24V with all major DC loads 24V. Then a small 12V system for the few things that are only 12V. It's typically a single battery and a DC/DC charger.


But you got off on the heat generated in an alternator, which can be a real issue as we all know. My suggestion was focused only on the alternator, not the whole power system.


When you double the voltage, you halve the current, and power loss drops 4x (roughly). So you can see that running at higher voltage is much more efficient. It would be a science project, but I'd consider an alternator that operates at 250 VDC, and feeds a Victron Skylla charger. The Skylla normally is powered by 230/240 VAC, but it will accept DC as well. That alternator putting out only 20A would be producing 5kw. It would be a total science project, with a number of possible pitfalls, but that's the concept.

[rgleason]

A step down DC to DC Victron Energy Orion 24/12-70 DC-DC Converter 70 Amps is about $150 and operates at about 96% efficiency. If that is able to reduce alternator heat output by using 24vdc alternator, such that it's continuous output would be significantly higher it might well be worthwhile, considering that these more expensive/complicated solutions might not be needed:

1. Remote Rectification - Mark Gasser's robust and well designed $600.
2. Remote Rectification -Quickflier 420amp $149 https://store.alternatorparts.com/qf...rectifier.aspx
3. J180 large case Alternator that requires custom install, instead a well designed and ventilated small Case alternator can be used.

for LiFePo4 continuous duty, it might well be worthwhile. Thank you for suggesting it.

The additional advantages are:

1. LiFePo4 Battery storage can more effective at 24vdc.
2. Reduced size and cost for Wiring: Alternator to the battery and if the DC/DC Step Down is located very near the 12VDC panel, most of the cables can be reduced in size.
3. Also any solar panel(s) can be optimized for 24v.

So I wonder if anyone knows definitively if 24v Alternators will really help by being able to run at higher continuous output and if so, how much?

Would it be better to get a 24vdc starter or just have a sealed cell battery for that which would act as reserve for the 12vdc system? This assumes the charging field current of the alternator can be interrupted automatically before HVD occurs.

[john61ct]

Things are complicated enough, do not further complicate things unnecessarily, stick to KISS 12V unless you have an exceptional known-with-certainty **compelling** reason to go higher.

[newhaul]

Originally Posted by tanglewood

Changing the whole system to 24V would help overall, but probably isn't practical. Lots of bigger boats are 24V with all major DC loads 24V. Then a small 12V system for the few things that are only 12V. It's typically a single battery and a DC/DC charger.


But you got off on the heat generated in an alternator, which can be a real issue as we all know. My suggestion was focused only on the alternator, not the whole power system.


When you double the voltage, you halve the current, and power loss drops 4x (roughly). So you can see that running at higher voltage is much more efficient. It would be a science project, but I'd consider an alternator that operates at 250 VDC, and feeds a Victron Skylla charger. The Skylla normally is powered by 230/240 VAC, but it will accept DC as well. That alternator putting out only 20A would be producing 5kw. It would be a total science project, with a number of possible pitfalls, but that's the concept.

what would be the hp required to run an alternator at 250 vdc? (20 amps)

This is an interesting idea
Then just run that thru a step down to 12 vdc that would be about 350 amps.