Hacking DSLR battery to power camera from power supply

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):

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.

Answer

There are many ways this could "go wrong".

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

  
  
  


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  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.)

  
  


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

  
  


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  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.