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Hard wiring battery toy to a DC source

Discussion in 'Electronic Basics' started by Eric, Dec 9, 2004.

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  1. Eric

    Eric Guest

    Hello all,

    I have three of those Star Wars animated sword battling figures (Darth Mul
    and the two Jedi dudes). When plugged into each other at the base, the two
    Jedi's gang up on Darth.

    Anyways, they each contain 4 banks of 3 AA batteries. I say banks, because
    each group of 3 batteries is isolated from the other group ... at least from
    the visible exterior.

    How do I use a DC converter with two wire (+/-) and wire up one of these?
    Should I just soldier up 4 wires, one to each + starting point on each bank,
    and another 4 wires, one to each - ending point on each bank, twist the 4
    positives together and hook to the DC +. Likewise for the - ?

    Actually, I tried this and didn't have any luck. Which leads me to my next
    question. How powerful of a DC converter do I need? If there a 4 banks of
    3xAA, thats 12 x 1.5 volts? What size of a DC should I use? The one I have
    is 3.7 volt, 350 mA.

    Thanks for reading and I appreciate your comments.

    Cheers,
    Eric
     
  2. You have to know more about how these banks of batteries are connected to
    each other.
    If they need so many batteries they need more current than this converter
    can deliver. Toys with motors in them often need a couple of Amps.

    If you want to continue this project you need to go deeper into the
    devices, find out what voltages are needed inside, how the battery banks
    are interconnected and how they are connected to the circuit boards inside.
     
  3. Eric

    Eric Guest

    Ok ... if I open it up, I don't suppose there's going to a labels
    inside which state voltage requirements, so how would I learn that?

    I was expecting that there would be a formula to determine the amount
    of voltage/amperage which is generated from 12 AA batteries, and from
    that I would be able to determine how powerful of a DC converter I
    would need.

    If I open it up and see that each of these backs merely connects on to
    the next one, to basically make one huge bank of batteries, then given
    an adequate DC powersupply, I should just be able to hook the DC + wire
    to the start of the back and the DC - wire to the end of the bank
    ....... right?

    BTW ... here is a link to Darth Maul. He is one of three that plug
    together.
    http://cargobay.starwars.com/webapps/cargobay/item-detail/6725/5002
    Thanks,
    Eric
     
  4. Mike

    Mike Guest

    A battery has a fixed amount of charge. It's "charge" life depends how fast
    a load draws charge from the battery. If load B draws twice the amount of
    current than load A, the batteries will last half as long as they did in
    load A. Batteries are rated in milliampere hours (maH). This is the amount
    of current that can be supplied in an hour. For example, a "AA" battery with
    a rating of 1600mAH can provide 1600 milliamps for one hour.

    I have hooked up battery powered devices to plug-in adapters before. You
    need to determine the right polarity and the battery configuration (e.g. are
    all batteries in series? Or are they two parallel banks?).

    Best bet is probably to take a picture of the electronics and post.
     
  5. The batteries do not determine the current. Some devices draw much
    current, other devices draw less current. The size of the batteries can
    only give a hint of how much current will be needed.

    AA batteries can deliver 1 Amp, or so. If the battery banks are connected
    in parallell we might be talking about a few Amps.
    Yes, if they are connected in series, that works.
    If you had a multimeter you could use the low resistange range to be sure
    how the battery banks are connected.

    Another method is to insert the batteries, without putting on the lid on
    the battery compartment. Turn on power on the device.
    Then use a voltmeter to measure the voltage from one end of the battery
    bank to the other end.
     
  6. One quick way would be to get a separate 5V wart for each 'bank', and a
    power strip with plug. It'll cost about 10 bucks from a surplus place
    like www.goldmine-elec.com.

    Actually, a nice product that I haven't seen would be a wall-wart
    battery replacement, using flat cable. The cable would have to be flat
    enough to allow closing the plastic compartments. It could support
    different voltages, selectable using a switch, and offer 'blank'
    batteries that are just connectors for the other batteries required. I
    have a battery powered keyboard from logitech that eats batteries that
    would be a perfect application for such a product.

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  7. Rich Grise

    Rich Grise Guest

    For this, I use a stick and a couple of brass shims.

    Have Fun!
    Rich
     
  8. I have done this many times and I have used miniature crocodile clips or
    soldering to connect the wallwart to the battery connectors in the
    battery compartment. It is usually easy to remove a little plastic from
    the lid so the wires can be used with the lid on.
     
  9. That is what I'm using right now... :) Imagine how many people are doing
    this. What a market!

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  10. Rich Grise

    Rich Grise Guest

    "Get Audiophile-Quality Sound from your battery walkman at home! Just use
    our Nucleosynthetic Battery Supplantation System, yada, yada, ..."

    Batterized Ultimate Long Lasting Synthetic Hermetic Incomprehensible
    Technology! ;-)

    Cheers!
    Rich
     
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