This is a LP-E17 dummy battery that I made for my Canon T6i (EOS 750D), to avoid having to swap batteries while the camera is set up on a tripod.

I used two pieces of 5mm wide nickel strip for the contacts, but you can probably just use a cut down aluminum can or wrap the stripped wires around the terminals instead. I secured the nickel strips with small wood screws on the top and bottom (2.2 x 6.5mm DIN 7981C, but any small screws will work).

To make sure you don't damage the contacts when you eventually trip over the wires you can route the cables as depicted on the 3D print for strain relief.

I power the camera with by variable DC power supply, but you can just get a cheap DC-DC converter and use the power supply from an old device you are no longer using (f.e. laptop charger).

Please make sure to not mix the wires and keep the camera Voltage between 8V-8.5V!
The power supply should be able to provide about 2 Amps at 8V (~16 Watts) or the EOS 750D may give a "change battery" warning and shut off after some time.

If you want to play it safe (I did not), put a diode between the red cable and the positive terminal of the dummy battery to prevent reverse currents. You may need to adjust the supply Voltage depending on the diode's voltage drop.

When using the dummy battery the camera will probably think it's battery is empty and it may pop up some warning when starting, but everything will work fine anyway. Just respond to the warnings as shown in the images.