Amps Question

[MakersTeleMark]

I'm trying to calculate the amp/hr draw of my stereo system in the FWC. I don't have a head unit, it's a mostly direct connection from my mp3 player, so that power draw is negligible.

I have that wired to a 800w amplifier (4 ohms: 200 watts x 2 chan.;2 ohms: 300 watts x 2 chan.) which powers 2 8 ohm outdoor kicker speakers.

How do I calculate how much juice it's pulling from my battery?

I'm guessing 33amps, but that seems awful high, even though the sound is really loud and crisp.

 

[Utah KJ]

To produce 800W, an amp would need 64 amps @12.5V input; this assumes 100% efficiency. But wait... there's more... Your amp is rated at 14.4V @ 1% distortion assuming the amp is CEA standard (fantasy). So you first have to convert that number to real world (12.5V) which makes the amp about 560 Watts in real life. Then, unless you're going to be listening to sinewaves clipped by 3dB all day, you need to look at average power over time with music. The average listener will use 20% of the amplifier power listening to music so in this case about 112 Watts on average over time (112 Watts / 12.5V)2= 18 amps average assuming 50% efficiency.

Hope this helps.

 

[Utah KJ]

There are other factors like the Crest Factor of the program material but let's leave the truth valve where it is for now

 

[MakersTeleMark]

That does help tremendously and is in line with my expectations. I can run the stereo all day long (10 hrs or so) and my battery doesn't really blip that much if it's sunny and my panel is operating the way it should.