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I would like to power my DSLR for long captures with a power supply. I know the voltage and inner structure of the official batteries. The battery has 2x 3,7V cells inside with a circuit. People worked on this issue report that the battery's circuit is there to protect shortage or high current draw for protection. The circuit also provides authentication and ID to the camera. If this is not provided camera seems to know this and display error message.

What I am thinking doing now is to use manufacturer's own charger to provide the power, while battery is still attached. Meaning, that the power supply will simultaneously "charge" the battery and in parallel will supply power to the camera. The authentication pin can this way be connected to the camera.

I don't want to kill my camera, therefore I am asking, if this can go wrong in any way?

PS: I will keep the actual battery outside (for the authentication pin), while a 3D modeled/printed power supplied fake battery will go into the camera.

Plan (blue line: authentication pin): enter image description here

Edit: I forgot to mention that there is an adapter sold by Nikon to fit into the battery hole and power via external power supply. However, >$45 is too expensive for dumb power supply. If I can 3D print my part, then I can have the same thing for <$5. This is also a matter of principle.

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closed as off-topic by Enric Blanco, Dave Tweed Jun 24 '17 at 15:58

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Enric Blanco, Dave Tweed
If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Doesn't Nikon sell an adapter for just this purpose? I know that Canon has adapters for all of their DSLRs. \$\endgroup\$ – Dave Tweed Jun 24 '17 at 12:55
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    \$\begingroup\$ They even left a hole on the body to let you route the cable out. Read the user manual and you will find the Nikon dummy battery on the factory accessory list. \$\endgroup\$ – user3528438 Jun 24 '17 at 13:04
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    \$\begingroup\$ See Nikon's power accessory page. \$\endgroup\$ – Dave Tweed Jun 24 '17 at 13:12
  • \$\begingroup\$ Sorry, I forgot to mention the other reason, why I am trying to do this. I have edited my question. Eventually, if it works, I would like to open the designs for others... \$\endgroup\$ – Genom Jun 24 '17 at 15:01
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There are many ways this could "go wrong".

  • It almost certainly violates the terms of the warranty on the camera.

  • The voltage of the charger may be out of tolerance for the camera. (Obviously, the charger voltage must be significantly higher than the terminal voltage of the battery in order to accomplish its function.)

  • The charger is designed to safely charge a specific battery. The load of the camera will almost certainly confuse the charger's internal logic.

  • DSLRs are notorious for drawing a huge spike of current when a picture is taken. The charger may not be capable of supplying this current. The terminal voltage will sag, possibly messing up the camera's logic.

I have built external power supplies for DSLRs (for aerial photography). Trust me, they are not just "dumb power supplies". Tight voltage regulation combined with high peak current capability makes them non-trivial to design.

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  • \$\begingroup\$ Thank you, I was looking for such an answer. But is it "worth" trying? Are power supplies (AC-DC) bad at high spike current draw? May I use some good quality (high current?) DC power supply instead of the charger? I think the charger is smart and it communicates with the battery's circuit (nikonhacker.com). In this case it reads the battery's temperature. I need to connect that too. But What if i use another power supply? I have also read that camera can handle slightly higher voltages (e.g. 9V instead of 7.4V). Is this true? \$\endgroup\$ – Genom Jun 25 '17 at 0:01
  • \$\begingroup\$ I don't know. I haven't worked with Nikon cameras specifically. I do know that the Canons are rather fussy about the voltage. \$\endgroup\$ – Dave Tweed Jun 25 '17 at 1:27
  • \$\begingroup\$ One last question. I am not very good at electronics. But if I connect the original battery in parallel with a power supply. Wouldn't the battery compensate during high spikes (as they are designed for it), if the power supply fail to do so? \$\endgroup\$ – Genom Jun 25 '17 at 21:51
  • \$\begingroup\$ Yes, that's true, as long as you keep the wiring between the battery and the camera as short and direct as possible. But managing the state of charge of the battery will still be tricky -- they don't like being "float-charged" the way you could with a lead-acid or NiCad battery. A suitably rated ultracap might be a better idea. \$\endgroup\$ – Dave Tweed Jun 25 '17 at 22:20
  • \$\begingroup\$ Thanks a lot. I can connect some of my previous knowledge with the knowledge you are providing. I guess, ultracap(acitors) can discharge really fast. But I want to keep it simple and I know batteries themselves can handle it. I think I will go for it, as I described. For the float-charging, I was thinking about keeping the voltage on a "mid-level". Let's say when the battery would be 50% charged. This is what some notebooks are doing. For instance my Lenovo has an option to keep the battery alive longer by keeping it at 50%. \$\endgroup\$ – Genom Jun 25 '17 at 23:07

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