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How big a battery for a portable ( bike) sound system?


Have several amps and several speakers...

1 The most modest: a 2.1 computer sound system, probably ca. 5- 10 W RMS, 18 V

(I want to connect this to my 18 V portable drill batteries- how much run time ?)

2 The medium size: a 12 V  (2, or one) 16 A fused: 2 average 9 x 6 car speakers

3 The meanest: A big 4 channel amp, bridgable, 12 V, fuse is 36 A, a big sub and 2 average 9 x 6 car speakers

Volume is determined by the MP3 player, I hope being able to make it, amp inputs are selected by a passive crossover

I like the volume loud, but not extreme (< 100 dB).

Runtime 5 - 3 hrs.

How big a (car) battery I would need for solution 2 and 3 ?


seandogue5 years ago
Why not just use a bluetooth ready MP3 player (ie, your cell phone) and pick up a pair of bluetooth headphones? Then you need next to nothing in the way of batteries. Just use a portable charging unit for the phone, plug in, and go. You'll get ~4-8 hours of operation on the headphones from a single charge.

And you don't annoy the world by "sharing" your music with people who may not want to listen to whatever it is you like.
orksecurity5 years ago
Boomboxes got plenty of volume out of six D cells, adding up to something under nine volts -- admittedly with mediocre sound quality. I suspect that for five hours you're at more risk of overkilling this problem than running short.

Useful run time depends on how many watts the amplifier draws when you're using it (something less than its rated peak power) versus the voltage and ampere-hour rating of the battery you're using, together with what the discharge curve of that battery looks like. Amp-hours is amps per hour; watts is volts times amps; a bit of algebra will get you in the general ballpark.

Note that the speakers also play a part in which frequencies are reproduced how strongly. 9x6" speakers aren't going to put out "earth-shattering kaboom" levels of bass. They can still put out plenty to annoy everyone around you, though.
BobS (author)  orksecurity5 years ago
So I guess I can apply a scooter battery....