current draw from 2500 w?

Trying to figure out how big of an alt. I would need for a new set up. Guys, please check my math:

2500 wrms = about 179 Amps?

Also, should I add this to the amperage of my stock alt, and shoot for a HO one in that range? That would be 80+180 = 260A. That's a pretty big alt for a corolla, lol!

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Soldier: This is the worst part. The calm before the battle.
Fry: And then the battle is not so bad?
Soldier: Oh, right. I forgot about the battle.

Here's a nifty online wizard:   Alt Calculator

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Prepare your future. It wasn't the lack of stones that killed the stone age.

179A at 100% efficiency! Not gonna happen like that!

Depending on the amplifier, you could go as far as 50% BEYOND that... If you are using a Class D amp, then you'll add about 15% to that number, for about 210A.

Now... Since you will most likely NOT be running WFO all the time, a 200 would probably do the job. If you notice a LOT of light dimming with your stock alternator/battery (and you will) you will have to upgrade to something in the 200A range.

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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."

Pfffft... 100% effeciency. Right.

What about a 180peak/120idle alt.?

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Soldier: This is the worst part. The calm before the battle.
Fry: And then the battle is not so bad?
Soldier: Oh, right. I forgot about the battle.

I get 208amps. Law of conservation says energy is not created, so the 2500 watts output must be inputted. 2500w/12v=208.33amps. So at full volume but only RMS, your using 208 amps. I would suspect just over 400amps maxed, but this is what the battery is for. The 208 would be difficult side.

I've read somewhere that the vehicle will use 90% of what the alternator produces with all of the accessories on. So you alt will have about 10amps head room. At full volume, full time, you would need a 270 amp alt.

reax222 wrote:

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I get 208amps. Law of conservation says energy is not created, so the 2500 watts output must be inputted. 2500w/12v=208.33amps. So at full volume but only RMS, your using 208 amps. I would suspect just over 400amps maxed, but this is what the battery is for. The 208 would be difficult side.

I've read somewhere that the vehicle will use 90% of what the alternator produces with all of the accessories on. So you alt will have about 10amps head room. At full volume, full time, you would need a 270 amp alt.

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you sir do not know the law of conservation of energy...where does the heat energy come from??? Oh yeah...its the energy from the efficiency loss.

So 2500 watts output is NOT 2500 watts input.

Same reason why HP and Torque at the crank is more than power at the wheels in a vehicle.

Nice try though.

haemphyst wrote:

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179A at 100% efficiency! Not gonna happen like that!

Depending on the amplifier, you could go as far as 50% BEYOND that... If you are using a Class D amp, then you'll add about 15% to that number, for about 210A.

Now... Since you will most likely NOT be running WFO all the time, a 200 would probably do the job. If you notice a LOT of light dimming with your stock alternator/battery (and you will) you will have to upgrade to something in the 200A range.

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reax222, we've already discussed that. Not to mention the fact that the nominal voltage ISN'T 12 volts. It's closer to 13.8 volts, and SHOULD be around 14.4 with the engine running.

A Class A/B amplifer can only run 66% THEORETICAL MAXIMUM efficient. So for 2500 watts out, you need to put (more than) 3800 watts in. 3800/13.8=275A (engine off). Class D can run as high as 95% efficient (again theoretically), so for 2500 watts out, you need to put (more than) 2635 watts in. 2635/13.8=191A, in a wide-open situation. Less than that if the engine is running.

And I have 2200 watts RMS in my trunk, a red-top, and (yes, even I once believed caps "helped") 2F, in my Civic. I upgraded my alternator to 165A, and I've had no issues at all.

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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."

With or without the extra voltage or heat loss, 12v is a decent reference. I am aware of the limits of the classes, but there are a lot of variables that I don't believe are too important as long you go above the minimum set up by using RMS and 12v. I very well could be wrong, but it works for me so far and it was how I was taught to rough figure it.