Power and Ground guide--flawed?

While doing my homework....ie, checking out the Power and Ground Cable Size Guide to the left....it seems flawed.

Under the "Current Draw by Power", it doesn't make sense with the old 100W per 10 amp rule. Example.....40A for a 400W RMS amp. Efficiencies aside, you can only draw up to 40A with a 40A fuse installed in a 400W amp.

Am I loosing my mind or is the guide flawed?

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Bill
System in progress:
2 Kicker KX400.1's - 945w RMS
2 12" P3's in a ported box built by local shop
1 Kicker KX250.2 to drive the mids and highs
1 set Alpine SPR-136A for mids & highs

No, I don't think the guide is flawed. 10A@14.4v=144w

100w out, divided by 144w in = 69.4% efficeincy. A relatively close number for a class A/B amplifier today.

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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."

Okay, grant you that on A/b. How about class D amps?

Just trying to figure out what size alt I need for my 945W's. According to the guide, I would be pulling pretty close to 160A of current. Add about 65A for the vehicle and that's about 225A for just a 1000W system. Does that sound right?  Now I'm thinking I DO need to order that 200A from Alterstart instead of getting the 180A locally.

Man, what do you guys do with those 1500 to 3K watt systems?

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Bill
System in progress:
2 Kicker KX400.1's - 945w RMS
2 12" P3's in a ported box built by local shop
1 Kicker KX250.2 to drive the mids and highs
1 set Alpine SPR-136A for mids & highs

Class D amps will run around 80 to 85% efficient. While the pwer supply in a class D amp can run as much as 95% efficient, the outputs are quite a bit less efficient than the PS. Still, stick with the 10A per 100 watts rule. You can NEVER buy more alternator than you need...

945w / .8 / 14.4v = 82A Is that 945 watts total, or 945 watts per ampliier? I'm a little lost...

As far as a 1500 to 3000 watt system? I never run it wide open - it'd probably split my head open... LOL I have a 150A alternator, and two red-tops in my '01 Civic - I KNOW I will never get all of the power I bought on a continuous basis, but I get MORE than enough continuous power for the levels at which I listen to it... and peak power is also not any issue whatsoever.

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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."

Sorry, the 945W is from both amps strapped together. The first one I bought was 465 and the second one read 480, both from the birth sheets ( Kicker KX400.1's). When I say strapped, that's Kicker's term for daisy chaining.

Wow, 150A alt. That's a good bit of info. I think the 180A will do me fine then. Peak power......what is peak power.....someone oughta shoot the guy that started the peak ratings  lol.

I wont be running it at full power all the time either. But it WILL get  exercised every once in a while.  :-)

Thanks for the help!

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Bill
System in progress:
2 Kicker KX400.1's - 945w RMS
2 12" P3's in a ported box built by local shop
1 Kicker KX250.2 to drive the mids and highs
1 set Alpine SPR-136A for mids & highs