What does this camera battery circuit do?

Discussion in 'The Projects Forum' started by jt7747, Feb 24, 2010.

  1. jt7747

    Thread Starter New Member

    Feb 24, 2010
    Hi. First timer.

    I'm building a custom external battery pack for my Canon camera. I've used this technique before for compact cameras, but it's slightly different for my larger SLR.

    Basically you can buy an external AC to DC adapter which tricks the camera into thinking it has a battery plugged in. In fact, the 'battery' is a dummy plastic cell with terminals in the right place, and the DC supply is plugged into the dummy cell.

    Here's the kit info:

    I bought just the dummy battery. The camera expects 7.4V Dc so I intend to use 6 AA nimh cells to create 7.2V supply. This should work fine.

    When I prised open the dummy battery I was surprised to find a circuit inside with some capacitors and stuff. I don't understand what role it plays. For my own DC supply can I bypass this circuit, and hard wire my DC input onto the battery terminals that make contact inside the camera? I'll make sure I get the polarity correct.

    Or should I just hard wire into the DC plug socket. It's a bit confusing, the socket seems to have 4 soldered inputs, I thought it would have two, + and -.

    Any tips?

  2. bertus


    Apr 5, 2008

    The board will pass the voltage from the DC plug to the camera through the chokes.
    The capacitors are probably there to filter the noise from the powersupply and buffer high current peaks.

  3. jt7747

    Thread Starter New Member

    Feb 24, 2010
    OK Thanks. So I guess I don't need them. Working backwords from the terminals that connect to the camera inside its battery compartment, I plan to snip the connections to the two choke things (whatever they are) and then it should be easy to solder my DC source to the metal plate bit that has convenient holes in it.
  4. BMorse

    AAC Fanatic!

    Sep 26, 2009
    What I would do is leave the circuit intact and just connect your power source to the bottom of the power jack, or make an adapter to plug into it from your battery pack, these components on the circuit will not affect your battery supply....

    My .02
  5. jt7747

    Thread Starter New Member

    Feb 24, 2010
    Thanks for the tips. It's actually much more convenient to wire in my leads at the end of the circuit, after the chokes, simply because I can solder them more easily that way.

    On another note, I just found a small ish 12V battery lying around. What's the best/most efficient way to convert that output to say 3.6V so I could power my camera for AGES? I know little about transformers