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Old 06-01-2009, 07:59 PM   #1 (permalink)
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Connecting car alternators in parallel

What happens if I connect two car alternators in parallel? Can I connect three or four alternators in parallel? I just want a cheap way to increase power. I need 5.5kw for recharging a battery pack.

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Old 06-01-2009, 10:35 PM   #2 (permalink)
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I have no idea, but I would guess that it would work as long as the one alternator isn't enough to get voltage up to 14-ish.
Sounds like a neat idea - what's the strongest single alternator you can find?
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Old 06-01-2009, 10:36 PM   #3 (permalink)
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Oh, and this thread should be moved to Ecomodding Central.
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Old 06-01-2009, 10:52 PM   #4 (permalink)
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Quote:
Originally Posted by agabrielauto View Post
What happens if I connect two car alternators in parallel?
You get two alternators fighting for control of the system voltage.
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Old 06-01-2009, 11:02 PM   #5 (permalink)
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Hi Guys,

I thought i would throw in my .02 here. I'm a computer and systems engineer, so i have a little bit of insight here. I'm gonna say, you could run into problems. Most modern alternators are setup for active (computer) control. They are designed to top up your battery, and then run at the lowest level sufficient to maintain high voltage. If my battery is charged, the alternator will keep the voltage at around 12.7 volts. If the battery is discharged a bit, it'll charge at 13.5v. If the battery is very discharged, it'll charge at as high as 15V. The problem that i can see you running into, is that the first alternator to kick in will bring the voltage up above normal battery voltage. This will prevent the others from running. This alternator will run at the highest operating current it can, until the voltage sags down to regular battery voltage. Then the next alternator will kick in, and so on, until you are maxing out all your alternators. You won't be sharing the load between all of them. You could also cause controller instability, whereby the alternators kick in and out at high frequency, as all five try to keep the voltage at spec. It wouldn't be the kind of thing I'd want to do haphazardly. You should also be aware that most alternators are rated at a current at some RPM. So that 5.5 kw your after, will probably only be attainable at 4-5k RPM (if your going with the ratings). The biggest alternators i've seen are 200 amp at 12v. which is around 2400 watt.
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Old 06-02-2009, 04:55 AM   #6 (permalink)
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Thanks for your answers!

This site sell dual, triple and quad alternators mounting kits. They also have a 315amps alternator. But how can all these power could be feed into the batteries?
http://nationsautoelectric.com/gmtriplet.html

Last edited by TomO; 06-02-2009 at 11:42 AM.. Reason: fixed the link
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Old 06-02-2009, 08:44 AM   #7 (permalink)
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I think multi-alternator is semi-common among car audio peeps.
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Old 06-02-2009, 09:18 AM   #8 (permalink)
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So long as it's designed to be run in parallel you'd be fine. They would probably have a single controller and load them all up in parallel. I didn't know they made such a system!

Nice find.
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Old 06-02-2009, 11:44 AM   #9 (permalink)
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Couldn't one be in the normal circuit and the rest be used solely to charge the auxiliary battery pack?
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Old 06-02-2009, 07:05 PM   #10 (permalink)
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I think as long as you have only one external regulator hooked to multiple alternators field terminals it would work fine. That way each alternator increases its output the same, provided they are exactly the same alternator and have the same pulley.

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