Fat Battery Newb

Heya! I’ve been using an old Macbook w/ Plex and 2 4TB External WD Hardrives. The battery has started to puff up… and apparently, that’s not a good thing. So, I’m just starting out and I understand very little about what I’m doing. Any directions on where to start, what to read, what to learn would be greatly appreciated. I have, roughly, 72TB worth of content saved up, and need to keep switching HDs when I want to watch something. My old Mac also doesn’t play the HEVC files well, and I don’t understand why. The Fat Battery is a new thing, and I’d rather not die in a house fire.

I purchased this battery and followed a YouTube video. https://www.amazon.com/gp/product/B01GHHT2TY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1. Wasn’t hard to do at all. Keep track of the bottom screws because there are a couple different sizes.

Build a Nas and stop swapping hard drives. So far as your Mac is concerned you can replace the battery or remove it if mobility isn’t important