My Partner just loves to walk around with the MacBook and use it in different spots. I've installed a couple of AC-Adapters, too. However, she likes to run the Mac on battery only very much. Well, after 4 years the Akku got a little thicker, besides that it lost capacity (the loss in capacity wasn't that much - about 60% left from what it had in the beginning). I was just worried that the body-structure would be harmed so I searched on ifixit.com for replacement. Since the MacBook is still doing a very fine job after 4 years it's absolutely reasonable to get a new Akku and run it for hopefully another 4 years or even more?
quick and easy - just open the lock on the bottom, this will release the Akku, take it out, get the part-number (the one beginning with A....), enter the part-number in ifixits' search-box, verify you have chosen the right one, check out, wait about a week for delivery to Europe, put the new one in place, lock it, enjoy your ride.
What ever it is - just do it! Yes, you can!