Alternator efficiency

[Tesla]

Stumbled across this paper.
http://www.delcoremy.com/documents/h...ite-paper.aspx

Some intereting info, they indicate alternator efficiency is highest at 30-40% load and 2,000 - 2,500 rpm.

So maybe gearing down to 1:1 to engine and only activating alternator above say 1,800 rpm may improve overall efficiency.

[jeff88]

That is an interesting paper. It makes sense, just good to see it in one cohesive argument. Is there a way to determine the efficiency of your current alternator? I assume you can use a multimeter for the output, but how do you determine the amount of energy going into it?

I wonder if one wanted to have a more efficient alternator at a higher RPM, what would need to be done to make that work. More/heavier coils, lighter stator, domething else?

[Frank Lee]

That's one of the papers I looked at when I re-ratioed my alternator and water pump: http://ecomodder.com/forum/showthrea...ork-20558.html

[JRMichler]

I too much driving at 800 engine RPM, where the alternator is barely keeping up with the base electrical load. That's 25 MPH in fifth gear.

I'd have to put in a deep cycle battery if I re-ratioed the alternator. I'd be better off to do a full alternator delete with a switch for those long trips.

[jeff88]

Is there a way to do a pulley clutch? Like an A/C or hydraulic fan, but instead of the clutch forcing it off of the drive belt, it would just change over to a different size pully. Then at idle speeds, you can have 2:1 or 3:1and at higher speeds it will "clutch" to 1:1.

I guess that wouldn't really possible, since it would change the size of the belt needed to function properly.

[mort]

Originally Posted by JRMichler

I too much driving at 800 engine RPM, where the alternator is barely keeping up with the base electrical load.

Please note the alternator efficiency is at alternator RPM:

On all the cars and trucks I've seen the alternator sheave is much smaller than the crankshaft sheave, maybe 1/4 as big for old Chryslers.

-mort

[RobertISaar]

Originally Posted by jeff88

Is there a way to do a pulley clutch? Like an A/C or hydraulic fan, but instead of the clutch forcing it off of the drive belt, it would just change over to a different size pully. Then at idle speeds, you can have 2:1 or 3:1and at higher speeds it will "clutch" to 1:1.

I guess that wouldn't really possible, since it would change the size of the belt needed to function properly.

not only the size of the belt, but also the angle at which it would run. serpentine belts don't like being run like that at all.

[jeff88]

Originally Posted by mort

It looks like, according to this graph, the alternator is not even producing current until around 1200 RPM. So what is happening during idle? Does the efficiency go down because it has to convert high voltage down to 14 volts?

Can anybody answer my original questions: how to determine your alternator's efficiency and how to make an alternator more efficient at a higher speed?

[RobertISaar]

that 1200 might have been the first test point. assuming a 2:1 pulley ratio(which is pretty slow compared to a lot of the units i've had), that's a 600RPM idle. assuming 3:1(which is pretty realistic for my applications), that's 1800 alternator RPM, which is 40 amps or so.

[redpoint5]

Originally Posted by Frank Lee

That's one of the papers I looked at when I re-ratioed my alternator and water pump: http://ecomodder.com/forum/showthrea...ork-20558.html

Did you ever get a feel for the ballpark % efficiency gained from stripping all of those accessories out and running reduction ratios?