The Nikon D3100 is a great camera for the price, the bottom end of Nikon’s DSLR range. Being a bottom-end camera, a few things are missing, like an external power connector. I’m using this camera in a fixed setup for slide scanning. The 1080p live view makes an excellent way to preview slides on an HDMI monitor, but this will drain the battery quickly. One option is to use the Nikon EP-5A, which is basically a battery-like plug for the camera, which then attaches to the Nikon EH-5A power supply. This will run you about about $108 at B&H. A spare battery will run you another $50. None of the third-party batteries available apparently work in the D3100, as Nikon puts some sort of inkjet cartridge-style money-sucking chip inside their batteries. (I’m sure the vast camera accesory factories in China are working to overcome this issue).

It turns out the answer to both these problems is a third-party D3100 battery grip, $20something from Amazon.

The left-hand battery slot in the D3100 will take the $8 third-party batteries, as the camera is happy as long as it can see a Nikon battery when it starts up. I decided to add a barrel type power jack so I can power the camera off a power supply. I suppose it’s possible that all these infidel non-Nikon parts could cause the camera to explode, so don’t try this at home, kids.

The battery grip contains a circuit board that runs the whole width.

I attached the barrel plug to the left-hand (“infidel”) battery slot. In this photo, Green is – and White is +. Most DC power supplies are center-positive, and so I used that scheme here. I picked a spot for the barrel plug that puts it right against the battery slot so it can’t easily pop out. I carefully drilled a hole in the case, squared it off, and hot glued it in.

It works perfectly. You can even remove the genuine battery once the camera is booted.