For whatever reason, the Fitbit One I have began giving shorter and shorter returns on battery life until it just petered out. Over the course of troubleshooting this with Fitbit support, it was concluded the device was faulty and that I should recycle it - no problem, I have a couple of laptops and a desktop PC from clients (properly sanitized of course) ready to go to the electronics recycling center anyway.
I was, however, intrigued by the inner workings of the device and wanted to take it apart. This proved to be trickier than I had expected. I wound up having to pry the metal back off the device in order to get into it - this is a mistake, in case anyone was hoping to repair their own device, but I’ll come back to that later.
I had assumed from the divot on the back of the plate that there would be a pair of hooks behind the plastic shell that the metal plate slid and clicked into, but this wasn’t the case. As you can see here, like the battery, the metal shell is simply glued into place, and like Darth Vader’s helmet makes a satisfying sucking sound when removed.
On the left of the photo you can see the vibrator motor used for the (quite effective) “silent alarm”. I didn’t look up the model but I assume that it’s probably an older cellphone vibrator motor, something mass produced and relatively inexpensive while still being relatively small - it takes up nearly 10% of the device though.
So I lifted up, clipped off the li-on battery here, and exposed the pcb the battery was connected to (and of the device, obviously). This is when I noticed the board was too large to fit through the aperture of the plastic hood that I’d pried the metal backing of. Sure enough, and I couldn’t get a good shot of it, there is a seam running along the inside. The clear plastic shell is actually two parts:
Although the glue around that seam was much stiffer - not gummy like that behind the metal plate, some kind of cyanoacrylate, that would be the ideal seam to find a way into if you were interested in salvaging the device or replacing the battery. Obviously you’d probably want to spend a bit more time at than I did - particularly if you’re not expecting the replacement in the mail soon (; I did a fairly good job of mangling the device.
If you’re curious about that miniature QR code, it must just be inventory/serial number. It scanned out as a series of numbers, and appears to be attached to the main CPU? It appears to have the largest number of connections to the board in any case. The accelerometers are fairly small these days and could be any of the two or three other chips. No jewelers loop to get a read off of them though so didn’t bother looking them up.
I didn’t get a picture of the front of the board, but it was just the display panel, the button sensor and the bluetooth antenna which ran across most of the front.
Anyway, I couldn’t find a take apart online for the Fitbit, so I figured I’d take the opportunity to throw one out there.
Sorry for the poor photo quality and lighting, this was a quick bang ‘em up job before tossing the sucker away with the rest of the recycling.