My left earbud was not holding a charge through the night. So I followed along with the video in Spanish but instead of a heat gun I used the ifixit microwave heat pad. It took a few times in the microwave for 30 sec and resting the ear bud on it for about 3 min to get the shell to loosen up. The shell was still a pain to get a part and the battery and plastic holder stayed to connected to the outer shell. Fortunately I didn't break the ribbon cable and was able to use a pick to pull the battery and holder out of the outer shell. I also dented and scratched the shell along the seam to get it apart. I wonder if the heat gun would've been a better option?
After removing the foam from the old battery and placing it on the new one I carefully replaced the battery and snapped the battery holder on the inside shell and made sure the connectors were back together. I then used a few dots of the E-8000 glue and used a wood clamp to hold the shell together. The battery is now charging and I verified it connects to my phone. Now we'll see how it holds up tonight.