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Noob powersupply question

Discussion in 'General Electronics Discussion' started by badkarate, May 28, 2013.

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  1. badkarate

    badkarate

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    May 28, 2013
    I've got a police scanner, this model, that I want to make a battery pack that will power it. With it being tornado season here in Kansas, blackouts are frequent, and this would be very useful. The power supply for the radio is 12v at 300 mA. If I were to buy a battery that is rated at 12v and 4800 mAh, this would work for 16 hours optimally, right? This is the battery I'm looking at. My plan is to switch the male connector on the battery with one the will fit my police scanner. Should this work?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Several issues:

    1) The actual power consumption is probably less than 300mA.

    2) The 4800mAh rating of the battery may be "optimistic".

    3) You may not wish to discharge the battery all the way.

    4) The battery voltage will vary according to charge.

    The practical upshot is that you may get less than 16 hours. The variation in battery voltage may be a problem for your radio, but it may not.

    Since these are Lithium batteries, you need to be careful that you don't discharge them too far (it will kill them).

    All those things aside, I think it should work.
     
  3. badkarate

    badkarate

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    May 28, 2013
    I figured the 16 hour thing was being pretty optimistic. If it runs for a couple hours, it will be perfect. What can I do about the voltage variation? Install a capacitor?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    In the first instance, I would just try it and see how well it works. If it turns out to be a problem, *then* you can do something.

    Since the problem will be that the voltage will fall below 12V (it's likely to start out at around 12.6V and fall to perhaps 9V at effectively complete discharge) rather than rise significantly above it, there is almost no danger of damage to the radio -- It may just not work well near the lower voltage.
     
  5. badkarate

    badkarate

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    May 28, 2013
    Just an update on the project. After changing the power jack on the battery cable, it works. Thanks for the help.
     
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