Run time of an audio amplifier on batteries

[jtvang125]

If the amplifier is spec'ed at 50w x 2 @ 24V 6A and I have it connected to 2 12V 12ah sealed lead acid batteries in series, that should give me a theoretical run time of 2 hrs right? Of course I'll never be running it at full blast constantly so I should see a much longer run time?

 

[Jimbo67]

Hi. As someone who's designed a few audio amps, and taken a keen interest in it, I can tell you this.

Firstly the maximum power is always to be taken with a pinch of salt, so I agree on your maths, use the maximum input to the amp, not the claimed output.

The main thing though, is that actual power of a typical music programme is only about 10% of the maximum possible power (it varies quite a bit according to type of music too). So even if you have the thing cranked up to the point of distortion, I reckon you could get something like 20 hours run time. If you're running it a moderate level, you should be seeing longer runtimes still.

Hope this helps.

 

[jtvang125]

Thanks for the info. I guess I am overthinking things a bit here. I'm not looking for a run time of days but enough to last a day or two at moderate levels and the occasional blast for the favorite songs. So I guess this will work just fine, maybe even an overkill.

 

[mindless1]

For much higher efficiency you should go with a class D amp. Maybe it is class D.

The only realistic way to figure out what kind of runtime you'll have is setting it to the desired volume and measuring input current. I mean theoretically if you know every spec on every part then you can mathematically make a ballpark guesstimation but measurements are more real world accurate.

 

[HutchinsonJC]

If you assume that the 50 watts x2 is an accurate reflection of what would be consumed at loudest volumes, then yes, your 2hr figure is correct. As an above poster said, the volume levels of any given song often bounce around with higher volume points of the song and lower volume points in a song. I'm not sure if I agree with the figure of 10% power usage on the average song, but then I tend to lean toward songs with a lot of bass.

Which by the way, the low frequencies (bass) are what will consume the large majority of the power. If you can set equalizer or options to turn that down a touch (to your taste) you should be able to extend your battery life that much more.