[masklinn]

If you have a 2012 you can easily replace the battery yourself, just check the relevant ifixit guide for the screw bits you need, IIRC from my 2010's replacement the battery has a pair of screws (one of which I think is behind the HDD bracket, though I may be misremembering) and an adhesive strip on the back which can easily be overpowered (though it's probably a better idea to soften it using heat from the trackpad side).

According to coconut I replaced my battery back in 2017~2018 or so (battery was manufactured in October 2017) and it was a breeze. "New" battery is at 6934/7000mAh (99% capacitity).

[ryanhuff]

According to ifixit, just 106 easy steps to replace and re-assemble! :)

[d0gbread]

I think there are early and mid 2012s that differ quite a bit. I have a mid 2012 and the battery replacement is a nightmare. I'm waiting for my 14" to arrive, I'll switch over, then give it a go so I can hand me down the 2012 with some life in it. And if I blow it so be it.

[ryanhuff]

You must have the 2012 retina!