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I have a problem with my charging system in my 66 Nova. Well maybe it's not the charging system as much as it's the stereo system. I just installed a complete competition stereo in my car last Wednesday. It has 1 800 watt amp for each of the 3 JL Audio W6-15 15 inch woofers and another 400 watt amp for the mids and 200 watts for the highs. I count a total of 3000 watts. I know my charging system is WAY over worked, I can see the head lights dim dramatically when I drive, even at high way speeds, and I have been having problems with the amps cutting off after a short while because of low voltage. I don't know the formula to convert wattage to amperage so can anyone help? I thought about changing to a CS130 alternator off of an 80's car. Will this produce enough amperage? If not what alternator should I use? Are there any factory alternators that will work? Or will I have to go with an aftermarket alternator? I saw one in a magazine rated at 140 amps, is this enough ?
Thanks for the info ahead of time.

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Yeah I know a couple of formulas but if I rattle them off they won't help you. The wattage you added up is the output wattage of your stereo system. It has 0 to do with what your stereo and power amp will draw from the battery. The easiest way to determine that is from the papers that came with the units, a sticker indicating current draw (amps) on the back of the unit, or the recommended fuse size for your units.
You really only care about amperage. That's what the alternator is rated at.
Let's say your original alternator is rated at 60 amps. It's stamped on top of the alternator. Car was happy with that. You go and add in a stereo that wants 15 amps and a power amp that wants 30 amps. You should consider putting in a new alternator of no less than 105 amps to put you back where you started. Hope that makes sense.
BTW
Don't crank it up in front of my house. It annoys the dog.
John
 

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Hello;

The amps will probably be at most 50% efficient, or at least that's a good number to use. This means they will require 6000 watts to output 3000.

Of course, the amps are not outputting a constant 3000 watts. It is probably more like 1/10 of that number. This means that your amps probably require about 600 watts continuous. Divide watts by voltage to get current. This gives around 50A of current.

The current alternator you have is a 63A unit, so it is basically just keeping up to the stereo. Put all the other car load on it and you can see why it isn't working. For that load, I would recommend, as a minimum, a 105A alternator. Just make sure to upgrade any wiring from the high current alternator to the battery or you could have an electrical fire on your hands.

Have you installed a second battery or capacitors? That helps with the headlight dimming problem, which may not go away with a higher current alternator.

Just remember, if the alternator can't keep up with the average current draw then the battery will eventually go dead. ie, the battery must be charged more than it is discharged.

Peter
 
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