This mainly pertains to the high end stereo guys here.

I am trying to figure out how much pull on my alternator I am getting from the amp.


And I beleive it's this formula



I = (Po - n*Po + Po) / V

Now

I = amperes
Po=RMS
n=efficiency
V=voltage

So for me its:

I = (3000 - .8*3000 + 3000) / 13.8

So I do this

3000*.8 and i get 2400


3000-2400=600

600+3000

3600/13.8

260.87 This is my amperage draw correct?



and if Im correct for everyone else heres an easier equation for this:

I = (2-n)Po/V


So for me this would go

1. 2-.8 =1.2

2. 1.2*3000=3600

3. 3600/13.8

And there we go. 260.87!!!!!

 

brilliant conclusion!!!! now i just gotta figure out my #'s for my stereo

 

Forgot to add.

Most class D amplifiers have an 80% efficiency rating!

Class A/B amplifiers usually carry a 60-70% efficiency rating

 

that sounds about right to me. on a side note, you may want to hit up a 270-300 amp alt in the near future. then you could bang fully eveywere you go and no worry of battery loss.

 

so is it a problem when my numbers look like this????

1.2*5000=6000
6000/14.4=416.67???

 

you'all need more amps. here is what mine are going to be:

if using sidewinders:


(7500-.8*7500+7500)/14.4 = 416.7


If using Napalms:


(13500-.8*13500+13500)/14.4 = 1125

 

I'm gonna do this out to refresh my memory and all so i dotn forget this


.8*7500=6000

7500-6000=1500

1500+7500= 9000

9000/14.4=625............

I had to have done something wrong here..............

Pat josh can u go over my math there and tell me where i went wrong?

 

no, your good dude, i screwed that one up. you math was right on!

 

gotcha i was like AW CRAP! thought i forgot how to do all this overnight lol

 

and that is with my 300A alt. I need to get another one