The SJCAM M20 action camera has been attached to the back of my Tour Easy for the last 16 months:

The Anker 13 A·h USB power pack on the rack provides juice for a week’s worth of rides, letting the M20’s internal battery keep its clock & settings alive between rides. I recently forgot to turn on the USB pack and discovered the camera shut down just after I cleared the end of the driveway.
As you should expect, the battery had swollen so much its pull tab … pulled off … when I tried to extract it:

So, we begin.
Pry off the trim ring around the lens by jamming a small screwdriver in any of the three slots:

Then pry off the entire front panel:

Thereby exposing the battery’s rectangular protrusion and three contacts next to the optical block:

Avoid shorting the brass terminals with, say, a small screwdriver, while shoving the battery out of the camera until you can grab it with your fingers and haul it out the rest of the way:

Yeah, that puppy looks all swoll up:

Remove the all-enclosing label to reveal the bag inside:

Pull the bag out to reveal the protection PCB:

Snip the wires and salvage the case against future need.
I bought the camera with three batteries, all three of which are now similarly swollen. I also got two official SJAM batteries with an official SJAM charger; both of those batteries seem to be in fine shape. I expect the codes on the five bags would reveal two different lots, but I’m not going to sacrifice a nominally good battery to find out.
All three swollen battery bags show the same BEP 782633PL
lot code and 1704
date code. I bought everything in January 2018, so those batteries had been sitting on the shelf for the better part of a year. Maybe that’s why they offered a “deal” for two spare batteries along with the camera?
Installing one of the unswollen batteries, reconfiguring the camera’s settings & clock, and giving it a charge from the Anker USB pack put it back in operation.