Saw your post on my original comment. Easy to replace battery, their is a link via I-Fixit battery guide on MacBook Pro 2011. Apple got sued in EU court for not allowing third party batteries. I do not know if you still have MacBook Pro 2011, hope it helps. Sadly, Apple put “end of shelf life” with this machine and High Sierra will NOT upgrade due to Apples “2015” or later MacBook requirement. This is stupid and forced “end of shelf life” so you buy a new machine, even though you meet hardware requirements. I smell another lawsuit.
You can max out your RAM on any MacBook just about because of the quality of design. I added two sticks of 8 GB of RAM for a total of 16 GB. Apple say my MacBook Pro late 2011 can only support 8GB.