Got an old Sena that stopped taking a charge? What do you have to lose?

I bought this Sena SMH10 motorcycle helmet communicator more than eight years ago, and it is way, way out of warranty. This spring I noticed the battery would die after about half an hour of use, which means it's pretty much dead. It used to hold a charge for 8-10 hours of chat time. I had noticed some tutorials online and decided the "non-user-serviceable" gamble was worth it, ordered up a new battery and prepared the surgical table.

If you are brave enough to attempt this, know that you might be wrecking your Sena. I figured that since mine didn't really work anymore I didn't have much to lose, except the $15 that the new battery cost me. Here's how I did it. Be very careful if you attempt this. Lithium batteries can be dangerous, as can knives and all other tools. I know you know all of this but I gotta say it anyway.