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Boombox backpack

Discussion in 'General Electronics Discussion' started by bc30629, May 26, 2011.

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  1. bc30629


    May 26, 2011
    Hello there,

    I am engaging in the world of electronics a bit to build a boombox backpack to help with promotions for my company. I have read up on a few different builds that others have done but I have questions about amplifiers and batteries.

    Others have recommended getting a small mini amp that puts out like 40 watts per channel. I have seen a few of these on ebay and such but I have also seen much larger mini amps at say 300-500 watts.

    We want this backpack to be very loud but we also want the batteries to last a while. I was going to get a 12v 7ah battery pack to run the amplifier. What would the power vs. efficiency equation be like here?

    Basically looking for suggestions that will keep me as efficient as possible and to keep me loud but keep my going.

    Thanks for any help.
  2. davenn

    davenn Moderator

    Sep 5, 2009
    well for a start lets look at you power supply

    12V @ 7AH thats going to give a total of 84W for an hour, and due to the battery voltage dropping, that figure is also going to drop off. You DONT want to discharge the battery below ~ 10V else it can destroy the battery's ability to recharge.

    So lets be conservative, lets say a total power dissipation of 75W for an hour.
    Assume an amplifier efficiency of 80% ( you may not get that) that means the max output power from an amplifier would be 60W for that hour period before the battery is discharged.

    there's some ballpark figures for your to consider

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