How to calculate power consumption (amp hours) for a car stereo?

Submitted: Saturday, May 31, 2008 at 21:45
ThreadID: 58238 Views:31378 Replies:4 FollowUps:0
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I want to calculate actual power consumption of my car stereo, for the purposes of planning a dual battery kit.

1. The head unit says "4 x 52W". I've only connected 2 speakers to it. I'm guessing "4 x 52W" is the peak. Assume 100W? Probably too much but anyway...
2. The standalone amp says "4 x 50W RMS". Assume 200W?

Can we now calculate the power consumption? I've used a few web calculators that indicate 300W RMS equates to 14.5A (ref: Car amp calculator)

So to calculate amp hours, I've done: 14.5A x 4 hours x 2 days = 116AH (amp hours) used. This seems massive to me ... and of course would add heaps to the battery requirements (ie. $$$!) of a dual battery project.

Have I got it right? Am I better off going to an auto-elec and getting them to physically measure the power usage? I do have a multi-meter, but it won't measure amps that high.

Thanks in advance for any pointers here.
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