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Old 03-29-2013, 12:43 PM   #1 (permalink)
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Alternator with magnetic coupling?

Hello people


Why not a alternator with magnetic coupling (Clutch)?
When the battery ist full, the shut down the alternator?

5-7% better efficiency?

cu

PowerPiston


Sorry my english is not good. I come from Switzerland.

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Old 03-29-2013, 12:54 PM   #2 (permalink)
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Welcome to the site. Alternators do not put a constant load on the engine. If the battery voltage is low they put out a lot of current. If the battery voltage is high they don't put out a lot of current. There really isn't a reason to physically decouple the alternator from the engine. Even the guys who do 'alternator deletes' usually just install a switch to stop the alternator from generating any power versus physically changing things.
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Old 03-29-2013, 12:55 PM   #3 (permalink)
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There have been ideas before about putting an air conditioning compressor on the alternator. From what I have heard the size of the pulley may cause issue with charging the battery because it is too big.
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Old 03-29-2013, 01:22 PM   #4 (permalink)
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the friction of the alternators is not to be underestimated
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Old 03-29-2013, 01:31 PM   #5 (permalink)
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Have you spun an alternator by hand? Its quite easy to do. The friction is nothing compared to everything else going on in a car.
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Old 03-29-2013, 01:37 PM   #6 (permalink)
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The main energy loss would be in belt friction, so you would need to have the decoupling on the crankshaft pulley. The problem is that the same belt often drives fans, power steering pump, etc.
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Old 03-29-2013, 01:39 PM   #7 (permalink)
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Quote:
Originally Posted by Daox View Post
Have you spun an alternator by hand?
No i haven't.
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Old 03-29-2013, 02:02 PM   #8 (permalink)
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You can spin an alternator with no load pretty easy. An alternator with load isn't so easy.
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Old 03-29-2013, 02:24 PM   #9 (permalink)
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...simply attach an AIRCONDITIONING CLUTCH to the alternator, that way YOU can control it's mechanical coupling & engagement whenever you want...or, have it electronically controlled by something.
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Old 03-29-2013, 03:45 PM   #10 (permalink)
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Belt friction isn't much either. Obviously more than no belt, but that's hard to do. The latest Toyota hybrids are completely beltless, so obviously there is some gain, but in the grand scheme of things? Like Daox said, it's not much.

The best would be like what Mazda is doing soon. The alternator charges when decelerating and turns off when accelerating, and charges a large capacitor to keep the charging system happy all the time. Maybe someone needs to invent a DIY version.

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