need to understand alternater.

I was wondering if someone could clarify or give some advice.  my Haynes manual says the alt is rated at 15 volts and the specs are 65 amps and 975 watts.  I ran the car with the lights on and checked the voltage at my battery, it was 13.9V when i reved it up and at idle it was only about 12.8V...is the alt fine?, if so how much should i get it rewound?  i read that the max the alt should put out is 14.4V but there are guys with 200+ amp alternaters...what does the higher amps do if the voltage rating can only be so high?  Forgive me if this sounds stupid. If your wondering what it will have to charge it'll be 2 MTX 350watt classD amps and 4 subs (not sure what yet...need a good brand, but not too $$) the deck is a 200watt deck, plus some neons, LEDs and other misc stuff.  I dont have light problems with the single 350 watt and 2 JBL (100rms and 400peak) so would a 150 amp / 14V alt be fine (or does the shope not change the Voltage output when they rewind? do I need to buy a differnt regulator then?)  thanks for any help.

Wow, that's a lot to get through... spacing and proper punctuation go a long way to getting your point across.

15 volts is probably the no-load voltage of your alternator. Do not worry about it only being 13.9v at the battery - that is only .5 volts lower than it usually would be. 14.4 is the nominal voltage of most cars today.

Rewinding is, in my opinion, a bad idea. BUY an HO alternator outright. Why? What happens if your HO alternator dies? (and they can, just like an OEM alternator) You will at least have one right at hand to keep you running, until the HO version is repaired.

All of the HO alternators you would buy today will be 12 volt alternators, which will do around 14 when the car is running. The alternator will ALWAYS put out 14 volts, but when your system NEEDS CURRENT, the alternator will be able to provide it...

If your amplifiers are 350 watt, and they are calss D, I would estimate about 80 percent efficiency:

350/.8=437.5 watts in
437.5 * 2 = 875 watts total
875 watts / 14.4v = 60.76 amps

Yes, I would say a 150A alternator would do you just fine, evn with the neons, lights, deck, and whatever else you might add later. If you can get a 200A (usually they are only a few bucks more, and MUCH BETTER bang for the buck) do it, and it'll last longer.

-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

sorry about the mess of writing.  Thank you for your reply, i appreciate it very much.  I'll check out what a 200A alt will cost me, i may wait untill income tax to buy one. Thanks again for your help, cleared a few things up for me

can anyone recommend a good place to get an HO alternator? i've been looking but can only find a few places

HOalternators.com

Alterstart

-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."