Power Adapter For Digital Cameras Without An External Jack

[Kusnick] is into using digital camera rigs for book scanning. The problem is that keeping the batteries charged is a pain, but there’s no external AC adapter jack which would allow him to use the mains. His solution was to build his own adapter to replace the batteries.

There are some fancy book scanning setups that allow you to just flip through the pages, but it’s much simpler to build a rig that uses two cameras. [Kusnick’s] setup is the latter, which means he’s found two inexpensive cameras that don’t need to be mobile. The first attempt at making an adapter featured a block of acrylic with the positive and negative contacts connected to a shielded cord which he then hooked to an external supply. The camera would come on and then turn off citing that the cameras were “for use with compatible battery only”. Turns out there’s some type of verification circuit built into the proprietary batteries. But the solution to that came quite easily; remove the circuit board from the battery and insert it in the adapter to trick the camera.

[Thanks Daniel]

21 thoughts on “Power Adapter For Digital Cameras Without An External Jack

  1. Very nice job! And good reason why you do that. Congrats!!!

    I can’t stand cameras and devices with special batteries (cartridges, etc) because they rip you off forcing you to by overprices accessories with the argument that “is to assure the best quality in your pictures, printing, etc” and protect you.. Right! That’s why my camera is a Canon A series that uses regular AA batteries ad regular SD memories.

  2. BTW: I hope the chip doesn’t have additional intelligence (as HP cartridges) where they count the amount of time they have been used and after a while they completely shut off “for your quality protection in your best interest”. It’s a time-bomb. I see too many components on that little board, so be ready to find more old batteries… Or plan B, hack the chip board! That would be fun! :)

  3. The chip/pcb is in the battery for a very good reason: protecting the lithium-ion cell in it from abuse such as:
    Overcharge, over-discharge, overcurrent, etc.
    It could explode without it….

    It also typically tracks the battery’s usage (charges and discharges) so the camera can tell how much charge is left.

    OTOH, It’s definitely a pain that the camera refuses to work without it… it should just refuse to charge the battery. (in a sane world)
    You might be able to find the chip at an electronics supplier though.

  4. Great Post!:) I’ve been wanting to use my old Olympus Brio D-150 Camera as a Web Cam. It’s only 1.3 Megapixel, but it has a nice Auto Focus and good Zoom features. It has an Analog Composite Video Out that works for sending the Video to my Video Input Card on my Computer. This could take care of keeping the Power Up at all times. Now all I need, is to figure out how to Keep the Camera from Auto Shutting off ever 20 Seconds or so…


  5. @Jonathan:

    Wait, the current is still being applied to the circuit (camera) regardless of the “on-battery” chip saying it’s not authorized. Proof’s in the pudding, unfortunately: the camera powers on with the custom feed to tell you it’s unauthorized. It seems that if you overvolted / overamped, the camera would fry / blow an internal fuse with or without the chip.

    Also, voltmeters have been determining how much usable charge is left, decades before these chips came along…

    So ya, none of your reasons seem valid to me.

  6. @Someone:

    Indeed, the camera powers on without the chip, because there’s no chip there to stop it.
    As long as [Kusnick] supplies power at a voltage that the camera expects, the camera would work perfectly fine if it wasn’t for the manufacturer’s silly lockout.
    The manufacturer could have decided to not power up at all (excluding the circuitry to communicate with the battery) if it didn’t detect a proper battery, but decided to tell you what’s going on instead (avoids returns for ‘broken’ cameras…)

    The chip is to protect the battery, not the camera.
    The problem would be if you use a nude Li-Ion cell instead of a battery, and try to recharge it/use it in equipment that does not know how to use a Li-Ion cell safely. These cells can be destroyed (spectacularly or not) if they are overcharged, discharged too low, or at too high currents. The chip protects the cell inside the battery by disconnecting it from the battery pack’s external connections if this happens.

    If the camera was overvolted by the external supply, it certainly could fry… or maybe blow a fuse… or maybe there’s an extra protection inside (if you’re lucky and/or it’s an expensive camera)

    As for determining how much capacity is left in a battery, you /can/ use a plain voltmeter, but consider this:
    Li-ion (and most rechargeable batteries, especially NiCd and NiMh) have a rather flat voltage for most of their discharge time (Alkaline batteries have a more gradual slope)
    Depending on the current actually being drawn from the battery, the voltage will sag, possibly more than the whole voltage difference over the flat zone!
    Depending on the age and type of cell, the curve will be different.
    This means it’s very hard to give accurate readings of how much capacity is left based solely on battery voltage (for rechargeables).

    The way the chips work, is by measuring how much current goes in and out of the battery, and integrating that over time.
    It also detects when the battery is full, and empty.
    These readings can be used to calculate how many mAh you can expect to draw from the battery, and how many it would store when full.

    Check out for a schematic of such a chip:
    http://people.openmoko.org/tony_tu/GTA02/hardware/GTA02/CT-GTA02.pdf [The Jonathan mentioned in here is not me ;)]

    Compare Alkaline and Li-ion discharges here:

    Note that every Lithium battery for cell-phone, etc. has three or more connections. That’s to talk to these chips.

    I think the chips are there /originally/ for a good reason, but I certainly agree with you that refusing to work just because there is no chip in the battery is over the top!


    PS: I’ve been researching Li-Ion batteries for work this week, which is why I’m so verbose about it, not trying to bash you or anything :)

  7. This “for use with compatible battery only” may end up being less evil than many here thing. This may be something as simple as the thermal contact check, seeing the thermal to ground resistance that is completely out of range, the camera may simply decide this is an unfamiliar battery that is dangerous to use and shut itself down. The guy should really try to just connect a simple 10k resistor between the thermal and the ground.

  8. @Boris

    Indeed, it might be as simple as a 10K termistor, some batteries do have only that.

    On [Kusnick]’s photos though, I think it’s a more complicated circuit: I can see 2 ICs, probably a protection IC and a ‘gas gauge’ IC, along with a stack of misc. caps and resistors etc.

  9. Hello folks. I’m glad that you liked the post. When I tried to make the camera work and got that “for use with compatible battery only” I tried first what Boris suggesting. It maybe work in many cases, but this particular battery has something “smart” inside.
    The only way I found to put it to work was using the internal circuitry into the fake battery. Cheers

  10. @Jonathan, i really can’t say what i see on that little PCB, maybe i am looking at the wrong pic or something. Fuel gauge chip on such a small battery ? I seriously doubt it. I would bet the entire thing is primarily a protection circuit, unless experimentally proven otherwise. Anyway, that’s just my 2 cents, based on personal experience of powering mobile phones using external power supply.

  11. @Boris

    I’m going from this pic (3rd on the forum page):

    I can see at least 2 ICs (No way I can read any numbers though…)

    The gas gauge doesn’t need to be particularly big (if physical size is what you meant)

    In a previous comment of mine (awaiting moderation for some reason) I linked to these:
    Which show a gas gauge(3x4mm) and protector IC for a 1200mAh smartphone battery (not a super high capacity either).

    I’d spy on my cellphone’s battery if it wasn’t half past midnight :)

  12. Having been too lazy to actually read the linked article and look at the pictures, I would guess this is a fairly standard setup of a micro to handle the lithium battery management and an eeprom that stores the battery identification information.

  13. @Urza9814 how do you find the battery life on cameras that use AA batteries? My friend has a point and shoot style camera that uses 2 AA batteries. She gets about 20-30 pictures. I use a entry level canon DSLR and get hundreds of pictures from the battery pack.

    I certainly wouldn’t be recommending cams that still use AA.

  14. @Stevie: sure, if you’re talking about AA _primary cells_; but if you use AA _rechargeable batteries_ as any remotely sane person would do, you get plenty of pictures out of them on most non-pro point-and-shoot cameras.

    And guess what, having AA batteries means one doesn’t have to buy expensive extra custom battery packs (AA rechargeables are dirt cheap these days) if one wants extra power at hand, or one can just buy a set of AA’s in a pinch anywhere; also, AAs will be around LONG after the specific custom pack is no longer available (No, I don’t change my gadgets three times a year just because there’s newer stuff out).

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