Help with making custom speaker box

Discussion in 'General Electronics Chat' started by PSnetwork, Jul 30, 2013.

  1. PSnetwork

    Thread Starter Member

    Apr 1, 2013
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    Hey guys,
    i want to make a little speaker box with amplifier,2x 5watt speaker drivers units
    and 12v 5Ah battery

    some questions:

    1. on the back of the amplifier written that the amplifier needs 12v supply and 5 amps. problem is, all batteries i've searched on ebay, dont has the info about the current, only volts and capacity (mAh, Ah). so how do i know the current?

    2. if the needs for the amplifier is at least 12v and 5 amps, can i buy a higher current than that?

    3. how should i charge the battery, i dont understand it.... watch the diagram below

    [​IMG]
     
  2. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
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    What are you trying to build cause the title has a custom speaker box and really you are trying to build a portable speaker system ???
     
  3. PSnetwork

    Thread Starter Member

    Apr 1, 2013
    30
    0
    Yes im trying to build a portable speaker system with rechargeable battery.
    i want to "store" energy and than discharge it.

    if you've seen my diagram, i've plugged the 2 cables from the battery to the amplifier back, now i can use the amplifier, but when the battery will end up, how should i charge it ?

    sorry for my bad english.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    5A is the maximum current. For typical listening levels the average current is likely to be significantly less. The battery can be as large as practical. The amp will only take the current it needs.

    Typically you don't want to draw more current on steady basis of more then perhaps 1/10th the AH rating. Thus for a 7AH battery you shouldn't draw much more than about 0.7A average. Short bursts of higher current are fine as for large bass beats. That value will allow the battery to supply power to the load for about 10 hours.

    A typical auto battery may have a capacity of about 80AH. The 5000AH you show in you diagram would be a humongous battery.

    To charge the battery you connect a battery charger appropriate for the battery you select.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,368
    Don't know how they can get 500W from a 12V @.5A supply. Very misleading labeling.

    The Kinter MA-150 is reported to contain a Sanyo LA4508 power module with a quiescent current of 0.03A. If it draws 0.5A when driven hard (6W total), a 12V 5Ah battery should last for about 10 hours.

    3W per channel is about all this baby can deliver. Your 5W speakers are safe.
     
  6. Shagas

    Active Member

    May 13, 2013
    802
    74
    The maximum discharge of a battery depends on its battery chemistry.
    I assume that you want to use a lead-acid cell as I see in your picture .
    A 5Ah lead-acid isn't that big , check this one out

    http://www.gme.cz/oloveny-akumulator-npg5-12-12v-5ah-shimastu-p540-303

    It's only 1,5 kg .
    It's rated at 5Ah , and lead acid cells have a maximum discharge of 2-4 C if i'm not mistaken which means that a 5Ah battery can give a maximum of 15 , 20 or even more amps for short periods of time .
    You need not worry about the maximum current that the battery can give , only the voltage , which is 12 volts so that is fine . If the battery can give more current than you need then that is good because it will be easier for the battery.

    As for charging it , you can read more on
    http://www.bigginhill.co.uk/batteries.htm
    or on other links on google , but you can probably just use a wall wart (14volts or more) which goes into a 12volt or even 13 volt regulator and a resistor in series to charge it up


    If you want a smaller and lighter battery that will give you the same punch then you might want to look into Li-ion or Li-polymer but those need protection circuits and special chargers so it's up to you .

    Also it might help to put very large electrolytic capacitors rated at 25 volts with a capacity more than 10000uF across the battery . That way you will have a sharper response on Bass kicks etc (maybe a more experienced member can say more about this)
     
  7. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    Or just buy a Jawbone Jambox.
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,368
    My guitar "boom" box runs off a 12V 7Ah sealed lead acid battery and I can play bass all night on a charge:


    [​IMG]
     
  9. PSnetwork

    Thread Starter Member

    Apr 1, 2013
    30
    0
    so 5Ah capacity is drawing current of 0.5 amps or not ? if yes so it isnt enough and should i get 50 Ah battery (5 amps) for the amplifier and 12v+5amps wall charger ?

    and in my diagram the battery isnt 5000Ah, its 5000mAh (5Ah).

    im really sorry for my ignorance, english isnt my primary language.
     
  10. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    What?

    How many hours do you want to run the amp at full power?

    Your amp is drawing 0.5A, not 5A.

    At 0.5A, a 5Ah battery will last for 10 hours.
     
  11. PSnetwork

    Thread Starter Member

    Apr 1, 2013
    30
    0
    so whats mean the 12v 5amps at the back of amplifier, the maximum current flow or the need current ?
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    In the photo you have posted, I see POWER DC-12V .5A
     
  13. BobTPH

    Active Member

    Jun 5, 2013
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    That is a pretty hefty looking amp to be drawing only 500mA. I agree that in the photo it looks like .5A, but the OP, who can see the actual amp, says 5A and that make more sense.

    Bob
     
  14. PSnetwork

    Thread Starter Member

    Apr 1, 2013
    30
    0
    OK im really confused, if its written 5A at DC, so 5Ah will last for one hour?
    should i get a amplifier with lower current ?
     
  15. BobTPH

    Active Member

    Jun 5, 2013
    787
    114
    Depends on how much power you want.

    12V at 0.5A would be only 6W of power, which means more like 3W to the speaker.

    Bob
     
  16. Shagas

    Active Member

    May 13, 2013
    802
    74
    PsNetwork :

    Check your amp again to make sure if it's 0,5 amp or 5 amp .It's probably 5 amp
     
  17. PSnetwork

    Thread Starter Member

    Apr 1, 2013
    30
    0
    its 5A but i've decided to take another one, this
    but how do i need to conect the battery to make it portable ?
     
  18. Shagas

    Active Member

    May 13, 2013
    802
    74
    Well it's 12 volt , but you will need a bigger battery.
    Something like a 12 volt - 20Ah Lead acid cell.
    It depends on the speakers that you want to drive

    Edit: What music are you planning to play?
     
    Last edited: Jul 30, 2013
  19. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,368
    Check again. 12V @ 5A is 60W.
    That is not a 60W amplifier.
     
  20. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    700W music power, lol. Where do they come up with those numbers.
    It's rated 12V @ 2A from the wee wall wart.
     
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