Do you have 5 minutes? Then you can replace a MacBook battery.
My MacBook battery slowly degraded to unusable status. I stretched it as long as possible. All the way to the point that if it wasn't plugged in, it wouldn't turn on. This was mostly due to the battery being on back order
Fast, easy, simple. It took 5 minutes from start to finish. And that's because I spent time to blow out the inside of the laptop since I had it open.
Buy all of the tools from iFixIt if you don't already have them.
Follow the guide. This website is an amazing resource.
Tri-point Y1 Screwdriver
MacBook Pro 15" Unibody (Early 2011-Mid 2012) Replacement Battery