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I have a set of cameras mounted to a rig, in such a way that in order to remove the batteries for charging, I have to unscrew the complete camera, which is undesired. One option is a dummy battery with an AC-adapter, but this gets quite expensive for the number of cameras we are using. I do not need or want to power the cameras through the grid.

So my idea is to completely remove the battery from the camera and power the camera by using the original battery as an 'external battery'. My question is then, can I attach wires to the connection points inside the camera by twisting the wires around them, which are then 1 on 1 connected to the original battery on the other side (making sure the wires inside the camera are well insulated and unable to cause short-circuit) ?

I am not sure if this is theoretically possible, or if some pressure is required to the contact points in the camera in order for it to work properly (which is the case when the original battery is inserted).

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  • \$\begingroup\$ If you could get a reliable connection with the correct voltage, it would work. That is how DC couplers work. \$\endgroup\$
    – xiota
    Oct 9, 2019 at 11:05
  • \$\begingroup\$ "Penny wise, but pound foolish" because "wrapping" the wires can result in intermittent connections that can damage the cameras. \$\endgroup\$
    – xiota
    Oct 9, 2019 at 11:09
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    \$\begingroup\$ @hobbs Please post answers in the answer space rather than as comments \$\endgroup\$
    – mattdm
    Oct 10, 2019 at 0:05
  • \$\begingroup\$ What specific camera body and battery? and specific 50mm f/1.8 lens?Most Canon cameras with spring contacts in the bodies battery compartment use those for communication channels between the camera and battery. The actual power connectors have small "blades" in the camera that push into slots in the battery with spring loaded contacts inside the slots in the battery. \$\endgroup\$
    – Michael C
    Oct 10, 2019 at 2:48
  • \$\begingroup\$ You'll probably get more informed answers over at Electrical Engineering. \$\endgroup\$
    – MooseBoys
    Oct 10, 2019 at 5:16

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As far as I can tell, at least in my two Canon DSLRs you cannot wrap a wire around the battery contacts in the battery compartment. So you could have to implement some sort of connector, for instance by disassembling an old battery(*).

You also have to make an outboard receptacle with outgoing wires on which you can insert a camera battery, assuming you use the original camera batteries.

All this is going to take a lot of time for unreliable results.

On the other hand a no-name A/C coupler is around $20 (when the brand ones are $120), and will likely be more reliable and less risky than whatever you can build yourself.

(*) which can be risky, these things can catch fire if mishandled.

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  • \$\begingroup\$ I see, however, I figured that in my case (please see image: imgur.com/6TAQDPb) it could work by either wrapping wires through (1) the spring contacts, or by pressing some conducting material against (2) the connector plates, right? Thanks for mentioning the no-name couplers, but I have to check if this lies within budget, as we need a total of 10 of them. \$\endgroup\$
    – Jeroen
    Oct 9, 2019 at 8:53
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    \$\begingroup\$ Considering the risk of damaging the camera (that also becomes unusable for anything else), the DC coupler is still likely less expensive than extra cameras... (not mentioning time...). \$\endgroup\$
    – xenoid
    Oct 9, 2019 at 9:10
  • \$\begingroup\$ Re, "These things can catch fire." Discharge the battery before you start, and the fireworks will be significantly less spectacular/memorable if you happen to make a mistake. \$\endgroup\$
    – Solomon Slow
    Oct 9, 2019 at 13:45
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    \$\begingroup\$ @SolomonSlow Yes if you discharge them slowly but telling people to discharge the batteries will likely make some people try to short the leads. \$\endgroup\$
    – xenoid
    Oct 9, 2019 at 13:55
  • \$\begingroup\$ IIRC some lithium battery chemistries contain pyrophoric stuff especially when well discharged? \$\endgroup\$
    – rackandboneman
    Oct 9, 2019 at 19:47
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In addition to what has been said, you cannot be certain that a given camera design can deal with the extra (ohmic or inductive) impedance long wires introduce. The power supply circuit could get rather confused when it experiences a larger than expected voltage drop when attempting to draw a quick current pulse, and could do things like suddenly assume a faulty battery or reboot the camera. A DIY adapter would require a good amount of thorough testing, and probably a buffer capacitor of appropriate size in the camera-side adapter piece.

Also, risking a patently intermittent power connection is a good way to trigger rare firmware or hardware bugs that cause crashes, upset settings and data loss. It can also cause immense wear on some designs of power supply circuitry, since they will constantly redo what needs to be done to start up after power is connected - the circuitry to do that is often designed to "need a break" after doing its work, because it is in effect running overloaded for a short time.

A premade A/C coupler kit, maybe modified, will have all that design work already put into it.

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"Twisting the wires around the connection point in the camera" is all that is needed for giving you advice: forget it. That's not the way to create a reliable contact keeping your rig working. And it is a recipe for creating shorts. Those kind of shorts can let your battery go up in flames (and lithium flames are really hard to estinguish: don't even think of adding water). The right kind of short may also make the charging or charge control circuit in your camera go up in flames. You won't likely get reliable operation either.

And what are you going to save, considering 2nd supplier markets for power supplies? $15 per camera? What did you pay for the cameras?

At any rate, you could also reconsider your rig's setup. I have a camera with badly accessible battery flap that I mount in a lens clamp. That makes both battery and memory card easily accessible without unmounting and makes it quite more convenient to level the camera (or mount in portrait mode) than using the tripod does.

If your camera has enough of a fixed barrel part for a lens clamp (obviously you don't want to mess with a retractable barrel), that can be another option.

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  • \$\begingroup\$ Thanks, I am convinced not to use my solution. Cameras are sponsored and the project is based on very(!) limited resources and funding. Since the battery accesibility is rather a wish than a necessity, I am looking for a cheap, but reliable solution. The lens clamp might be an option. We are using Canon's 50mm F1.8 lenses, which do not have enough barrel part I am afraid. Would it damage the lens if a clamp partly covers the focus ring (not used since we are autofocussing)? \$\endgroup\$
    – Jeroen
    Oct 9, 2019 at 13:22
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    \$\begingroup\$ With all versions of Canon 50mm f/1.8 lenses except the most recent EF 50mm f/1.8 STM, impeding the movement of the focus ring (if you want to call it that- it's really just the end of the lens barrel) during autofocus operation can damage the focusing motor. Considering the the EF 50mm f/1.8 II has a plastic connection to the camera's lens flange, I would not recommend supporting a camera with a stand connected only to that lens. \$\endgroup\$
    – Michael C
    Oct 10, 2019 at 2:42
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For a lot of cameras, you can buy 3rd party "battery grips" that attach to the underside of the camera and slide into the original battery compartment. They are usually meant to house two or more of the original batteries for longer life, but in many cases also have a DC-input socket where you can attach a power supply or an even bigger external battery. These battery grips also contain the necessary electronics to signal to the camera that all is well in regards of power, so they are more reliable than "attaching wires to the battery springs".

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    \$\begingroup\$ Precisely what I was thinking. Many grips have a tray that just slides out for a change of battery. Or if AC power is needed, it's much better to hack a battery grip tray than the camera's battery compartment. \$\endgroup\$
    – GPS
    Oct 10, 2019 at 7:30
  • \$\begingroup\$ Third party grips usually cost more than third party battery couplers. \$\endgroup\$
    – Michael C
    Oct 10, 2019 at 8:20
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I've done something similar (not quite the same) for my old EOS 350D: I cut open a battery case (very shallow cuts - you only want to go through the outer plastic) and replaced the cells inside with a capacitor (only needed when using flash) and wires to come out to an DC power supply giving the same voltage as a fairly full battery. The wires come out through a little rubber bung next to the door, allowing the door to close.

In your case instead of the DC power supply I'd buy a cheap knockoff charger, take the electronics out and use it as a battery holder. You should use reasonably thick wires - something rated to a little over 1A (e.g. 7/0.2) should be enough if they're short, but if going longer, a higher rating would be in order (16/0.2).

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So in theory it should work. Simple Battery grips work the same. The batteries are outside of the camera and the grip just connects them to the inside.

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You can try to get the pinout for the battery. If the body supports extended grips (Canon EOS700 do) you can look for this pinout as well. Battery contacts are the golden blades down there and the array of golden spots is the interface for the grip.

All you need now is to mimic the battery/grip geometry and positioning of the pins, and deal with the battery lid.

As we are in 21st century, the rapid prototyping techniques (a.k.a. 3D print) are easy to access.

Get a 3D model of the battery/grip and build reliable contacts. You can easily disasemble the battery lid and build your own - with a hole big enough for the cable you want to feed through.

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In addition to what other answers have mentioned, with your Canon Rebel T5/1200D there is also the issue of the door position switch that is found in many battery powered digital cameras, including every Canon EOS interchangeable lens camera.

If the battery door is even slightly open, the switch will not be closed and the camera will fail-safe to an "off" power state. Most cameras that have battery couplers available also have a small flap that allows the cables to pass out of the battery chamber while allowing the battery compartment door to stay firmly shut. Any DIY engineering you might do would need to take this into account.

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  • \$\begingroup\$ Not really universal. I have used quite a few cameras that work fine with the door wide open. \$\endgroup\$
    – vclaw
    Oct 10, 2019 at 2:41
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    \$\begingroup\$ Indeed, the Canon 1200D that we are using requires the door to be closed. Also, the flap that you mention is present. \$\endgroup\$
    – Jeroen
    Oct 10, 2019 at 6:16
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    \$\begingroup\$ I don't think I've ever seen a camera with that "feature". In some, the battery will simply fall out (or be forced out by a spring) which enforces the off-state, in others the battery has a separate eject lever inside the compartment, and leaving the flap open does nothing (e.g. Sony Alphas). \$\endgroup\$
    – WooShell
    Oct 10, 2019 at 7:34
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    \$\begingroup\$ @WooShell You've never seen a single Canon EOS digital camera? They all have a release tab inside the door so the battery will not fall out, but the door itself has an interlock switch. I could be wrong about Sony', but every single Canon DSLR has such a switch, as does every Canon digital P&S I've ever looked at that did not use AA batteries. Ditto for Nikon. \$\endgroup\$
    – Michael C
    Oct 10, 2019 at 8:15
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    \$\begingroup\$ @MichaelC I have worked with a few Canons, but I don't recall closer inspecting the battery door or its safety features. My main cameras are Sony Alphas (A58, A7) which have a battery release tab, but leaving the outer battery door open does not have any side effects. Older Sonys (F505, F717, F828) spring-ejected the battery as soon as the door opens, which of course forced them to power off. \$\endgroup\$
    – WooShell
    Oct 10, 2019 at 8:36

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