Connecting a ginormous battery (Really simple)

Discussion in 'The Projects Forum' started by tlevine, Sep 10, 2010.

  1. tlevine

    Thread Starter New Member

    Sep 10, 2010
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    My bubble hat goes through AA batteries really quickly, so I want to attach an external battery. It takes 8 AA batteries, and I generally have to replace them about twice per hour. It also has a hole for a 9V 15W DC power plug, which I assume you can use instead of the batteries.

    I'd like to plug it into a ginormous battery pack. I clearly need the plug, the cable to connect that to the battery, the battery and something between the plug and the battery (whose name I forgot) if the electricity coming out of the battery isn't exactly what I want. I wouldn't be surprised if I need something else too.

    Could someone give me an idea of where to start looking for components? I'm particularly clueless about what sort of battery to get. I'm pretty sure I can assemble it once I figure out what parts I want.
     
    Last edited: Sep 10, 2010
  2. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    You might be better with Rechargable NiMh AA's.
    Since the power supply you mention is 9V 15W the hat cant be drawing more than 600mA. Rechargable batteries are slightly lower voltage, than 'normal' AA's but still at 1.2V (NiMh AA) each you have 9.6 volts with 8 installed.

    Modern NiMh AA's can regulaly have capacities of 2700 mAh (Millyamp Hours) or more.

    SO ...

    Your hat was probably gesigned for rechargable batteries in the first place, it would only need 6 regular batteries.
    Reasonable quality 2700 mAh AA's should last 4 hours or longer even allowing for heat and losses due to the constant use. Even a moderatly quick charger would charge the batteries faster than the hat discharges them so you wouldnt need that many.

    The thing to reduce a voltage if its too high is called a voltage regulator or sometimes DC to DC converter.

    If you used a car battery for example you would need a voltage regulator.
    How will you carry this huge battery?
    (Nice hat by the way)
    Al
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    You would probably be best served by using a SLA (Sealed LeadAcid) battery on a hip pack and run the wire to the hat.

    The hat WANTS 12v anyway, so there should be NO conversion or trouble.

    8 AA's (1.5v x 8) is 12v.

    I would say do that.

    Here are some to choose from.
    http://www.lowcostbatteries.com/12V-SLA-Batteries.asp
     
  4. tlevine

    Thread Starter New Member

    Sep 10, 2010
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    Yay!



    Dyslexicbloke, I forgot to mention that switching batteries is also really annoying as I need to take it off my head and unscrew lots of screws.

    And I need to carry a bag for the bubble solution anyway, and I already have a tube running from my head to said bag, so I'd been planning on putting the battery there.

    ---

    I guess I'm going with a 12V SLA battery as that looks easy

    Will it make a difference whether I connect the external battery to the hole or to the place for AA batteries?

    ---

    I see that the batteries on that page are not sealed for operation upside-down.

    retched, do you have a recommendation of where to buy those? Google Shopping gives a bunch of places, so I can find one if you don't.

    ---

    I'm also thinking about the size. I think it's more like thrice every two hours that I have to replace the batteries right now.

    If AA batteries have 2 AH and I need to replace them thrice in an two hours, I can expect a 12 AH battery to last four hours. This is actually a conservative estimate as the AA batteries aren't very dead when I need to replace them; they machine still runs, but it's not powerful enough to make bubbles.

    Or, since the hat doesn't draw more than 600mA, I can expect a 12 AH battery to 20 hours. This is a more liberal estimate as it assumes that the battery totally dies.

    So I'll estimate that batteries will last somewhere between those estimates, closer to the lower one.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Honestly I dont know of any that recommend upside-down usage.

    You may have to get a GEL type...

    Why do you want put it upside down?
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,783
    943
    Running a lead acid battery to exhaustion will damage them and cause severe sulfation of the plates; you also MUST charge them back up immediately. It is recommended to stop discharge of a 12Volt SLA when it reaches 11.5 to 11.0 volts. This is only 30 to 50% of the capacity the battery. And they are HEAVY Heavy heavy.

    As expensive as they are, I recommend using D cell size NiCd/NiMH instead. They are not damaged by discharging to exhaustion, and in fact, NiMH can be safely stored in this state.

    As for changing the battery pack out...connect a wire lead and put it through a hole in the hat's battery compartment. You could seal the hole with RTV silicone to keep it moisture tight. That way you wouldn't have to remove the hat to change batteries.

    Photogs for Television used to use a battery belt for live shots away from civilization or power outlets. This would be the best way to go. With a belt lined all around with D Cell rechargeables. check with a local Radio Shack if one is near you. They should have D cell battery holders. You will need 10 cells in series for a 12 volt level(under load), it will read higher than that with no load connected and fully charged.

    The NiMH batteries will be good for hundreds and hundreds of recharges. They will probably outlast the bubble machine you are using
     
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    Please note that most rechargeable D cells are actually C cells inside, you can pretty well tell by the weight.
     
  8. tlevine

    Thread Starter New Member

    Sep 10, 2010
    3
    0
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,783
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    Looks great. AND don't overlook places like HomeDepot-WalMart as sources for rechargeable NiMH batteries; of the affordable type. Names such as Panasonic-Rayovac etc.

    I'm sure you'll be happier with this arrangement than with 20 or more pounds of SLA 12 volts in a backpack. Lots lighter and easier on the spine. :)
     
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