300a alternator?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=107671
Printed Date: May 13, 2025 at 8:59 AM

Topic: 300a alternator?

Posted By: twobig86
Subject: 300a alternator?
Date Posted: September 24, 2008 at 3:13 PM

Does running my new 300 Amp alternator harder on the engine than say a stock 70 amp one? Some people I know are saying that it is going to take around 5 hp just to run it...im kind of confused about all this...

Replies:

Posted By: DYohn
Date Posted: September 24, 2008 at 3:20 PM

It takes power to make power, so yes, a larger alternator can place a larger load on your engine. 300a @ 14.4VDC = 4320 watts, which is equivalent to about 5.8 Hp. It will lower your gas mileage too (of course the worst gas mileage destroyer in car stereo can be the added weight of large subwoofer systems.)

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Posted By: twobig86
Date Posted: September 24, 2008 at 4:59 PM

So what about if its at idle say 100 amps? Would it be using roughly 2 hp or would it always be using the 5.8 hp...

Posted By: DYohn
Date Posted: September 24, 2008 at 5:04 PM

The power required by anything electrical, including alternators or amplifiers or anything else, is determined by the load So yes, if it's producing 100 amps it needs a lot less power input than if it's producing 300 amps.

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