If you want, you can use your Magic Trackpad 2 forever with no more battery waste. You may need to remove the battery. My battery swelled up and pushed apart the top & bottom, it was was either ending up in a landfill or goodwill, followed by a landfill, so this is what I did:
I pried the case (see details below), snipped the circuit board off the battery (there was a spark & battery heated up, but all OK), removed the battery, scraped off the silicone adhesive on the glass top case and the force sensor bars on the bottom case so tape could stick to the adhesive areas, used some 3M 300 LSE double-sided tape, reassembled, and it works exactly the same as before but only when the cable is plugged in.
As you pry open the case, look for those for sensor bars sticking to the top case - that's silicone adhesive. They're the only thing holding the top & bottom together. The silicone only comes off if you cut through it with something long and flat. Once cut through, the top & bottom separate.
CAREFULLY separate until you see the ribbon cable. It's held down with a little adhesive. With tweezers and being careful, you can unplug one side, so can fully separate top & bottom. Once you've scrapped off the silicone and installed some double-side adhesive, carefully use the tweezers to push the ribbon cable back in.
Once you get the ribbon cable pushed in all the way, press down on the ribbon cable adhesive to keep it in place and push the top/bottom together, making sure the glass and edge are aligned all the way around.
If you get the ribbon cable in correctly, it'll power up and work fine. Mine did.
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