Preventing Battery Bloat Suggestions

It's happened to me now, too. I recently bought a 2tb drive to upgrade, and while opening the deck, I realized that my battery was bloated.

I use my deck docked and connected to my TV as a retro-console emulator. I'd always kept the battery at 80% as suggested and thought it would be ok like that, but the bloat still happened. For now, I've changed the max charging to 50% and closed it back up while waiting for a new battery to arrive. Here's to hoping I don't blow up when changing it.

Does anyone have any suggestions/apps to help prevent it from bloating up again in the future? (or realistically keep it from bloating up too fast. Mine's only been with me for almost 2 years,) For reference, I live in a tropical place near the sea with bad moisture problems. Most days its either very hot or very cold and muggy.