Alternator Cooling

[sailingharry]

Originally Posted by d design

The problem is your trying to push enough current to compensate for such low voltage through small windings. I would consider going to 24V for more efficiency or consider a high voltage alternator with a step down inverter like the integral systems. You can do all sorts of technical mods but if you decide to sell the boat I guarantee the next owner will be cursing. KISS

I do suspect that 24V make much more efficient systems. But to your KISS point (and my budget point!), what does going to 24V do? And to your resale point -- will most buyers see a 24V conversion as a plus or a minus?



All new high power stuff (windlass, inverter, power winches, battery charger, autopilot ram). New starter motor, unless I run a dual voltage boat and keep the starter at 12V and find a way to charge it.


Lower power stuff (head, macerator, instruments, lighting, USB plugs, bilge pumps, etc) can all be run off a fairly large 24-12V converter -- but the fuse on that feed is 80A, so it's a bunch of current! Some stuff (fridge and instruments come to mind) is dual voltage, making that a little easier (although my suspicion on instruments is that they aren't really "dual voltage" but more "voltage regulated" and that they consume a fixed current regardless of voltage -- and so consume double the power at 24V vs 12V).



If it were AC, it might be easy to step the alternators up to 24V (or even 48V!) and use a transformer to drop back to 12V. But a 200A 24-12V converter ain't cheap!


You mention "a high voltage alternator with a step down inverter like the integral systems"-- is that a thing? Do you have a brand or link? That sounds really interesting! While I think 50V is a bit of a regulatory threshold (maybe not law, but UL, and that kind of stuff), I would think a 120V alternator "transformed" to 12V would rock! Maybe output AC, then transform and rectify. Of course, if it were easy, it would already be common....

[sailingharry]

Originally Posted by PaulCrawhorn

Those Aussie "blanket style" pretty compact folding pads can be put out, moved around and put away...

We aren't typical cruisers. We move. Last summer, in 110 days away from home, we stayed in 87 different locations. If we put them away on days we are moving, we never get them out! I also suspect that laying them on deck has even bigger shadow problems than the bimini.



They might work well for folks who prefer to spend weeks at anchor.

[d design]

https://integrelsolutions.com/

Lots of advertising to sift through but worth a look.

[PaulCrawhorn]

Originally Posted by d design

https://integrelsolutions.com/



Lots of advertising to sift through but worth a look.

Did their 48V alternator that Calder helped develop ever get public release?

I don't know if that used Al Thomason's Wakespeed / APS regulator or if they rolled their own?

I do remember it looked like it was going to be a super pricey setup...

[CaptainRivet]

Originally Posted by d design

https://integrelsolutions.com/

Lots of advertising to sift through but worth a look.

A 27000Euro bargain
For my cat quote was 41kEuro....for that i can buy a lot of gens, diesel and afford a mechanic for maintenance and repair

For sure cheaper per engine 2x140A heavy duty, so thats 480A in case of high latitude sailing. But i hate cold so barefoot sailor... And 1200W Bifacial solar fully support my needs in this case. Each alternator does 60-70A,so 120-140A is enough for the occasional top up when 5 days straight bad weather...

[CaptainRivet]

On most engines you can mount 2 Alternators...balmars small case outputs 170A, 128A at idle due to their spec sheet, standard alternator 70A +170A=240A, doubt a normal cruiser engine in 30-75hp range can handle 2x170A...

[sailingharry]

Back to the original question. The vast majority of alternators, from OEM automotive units to Balmar, as well as dozens of automotive after market "high output," and my Powerline, all have stamped steel fans. The 12Si had a much more "engineered-looking" fan.

Googling high flow fans, you can find nifty looking fans that don't cost all that much (~$30 each). But no one uses them. Do they really work, or is the biggest improvement found in the approving nods of the folks at the car shows? Are stamped fans used because, well, "they work.?"


Thoughts?

[Bill O]

Good job Harry finding those after market add-ons!

Fairly inexpensive and are better than those original powerline fans. Definitely worth the try, especially if the hot rod guys gives them the thumbs up.

[Sternwake]

I don't think the hot rod guys actually push their alternators very hard, much less compare the airflow from different fans and how it affect temperature when the alternator is being pushed hard.

I have rehoned the sliprings on a poorly reman'd alternator, whose one brush bridged both sliprings. I was spinning the rotor with a wirewheel touching alternator fan, on an angle grinder powered through a router speed controller at well less than full speed.

While I did not measure the rpm I spun it at, as I did not have an optical tachometer at that time. I was very much unimpressed with the amount of air the fan expelled radially.

I now have two alternators, the one that I rehoned the sliprings, and one with dual internal fans thay have the same 120 amp rating. I have K type thermocouples on both, on the casing adjacent to the stator. The one with dual internal fans runs consistently 25f hotter when the load on either is the same.

I think the distance the external pulley fan is, from the alternator body, greatly affects the amount of air that it pulls through the alternator.

I've not tried different external fans. The curved ones would seem like they should move more air, but if they actually do, that is an unknown, until proven otherwise.

I intend to push some colder air via ducting at the back of both alternators, at some point.

[sailingharry]

Originally Posted by Sternwake

The one with dual internal fans runs consistently 25f hotter when the load on either is the same.

Stern,


Did you transpose your response? If you wrote what you intended, it's very interesting and somewhat counter-intuitive. I've always assumed the move to dual internal fans was an improvement, but your data says otherwise.


Harry

[Sternwake]

Originally Posted by sailingharry

Stern,


Did you transpose your response?

Harry

I did not.

However, mine is an automotive application.

I've only fairly recently wired up the dual fan alternator, and I've not yet pushed both alternators hard, only equally hard, at no more than 50% of their rating.

I've not yet set up experiments with heavy loads intending to monitor the displays. I included the K type thermocouples in the external regulator harnesses, and attached them to the casing adjacent to the stator, which is why I have the data I do.
But, I need to sort out a pulley and matching V belts before I ask the alternators for 75+ amps each for 25+ minutes and can get a better idea of which design cools itself better, in my engine compartment.

Even then,
The dual fan alternator sits atop the engine, and the pulley fan alternator off to the side. My limited data collected so far, could have little relevance to a marine application, as the dual fan alternator could see more heat from radiator, than the one on the side. There's tons of variables I can't account for, and which could make my observations takes so far completely irrelevant to a marine application.

I've read that the switch to dual internal fan alternators, in Autos, was not so much for heat, but for noise.

I have collected some data regarding field current to rotors, at various rpms, and loads, and while the testing is incomplete, the most field current occurs at the lowest rpms when the batteries only need 50 amps to reach/ be held at absorption voltage, and the most heating of VR and Alt is at lowest rpms.

Just 200 more engine rpm can make ~25 more amps, and reduces VR and alternator temp considerably when only 50 to 75 amps are needed from the alternator.

All the testing requires a lot of effort and time, which I have found is better spent elsewhere, so far. Also with two alternators instead of one, My existing needs for juice are more easily met, and Ideal, has been tabled.