My car battery is almost 5 years old at this point and I have somewhat abused it by running it so low, very frequently. Not really a surprise that it's starting to go out. After sitting overnight it can be around 11.9 to 12.2Volts. Today it was 9.6V and somehow still started (super slowly).
Looked up how much batteries were at Walmart and I was shocked how much some can be. One was around 70 bucks which I WAS going to get, until my grandmother said "back in the day we used to have to top them off with water and they would just keep going, they don't make them how they used to" something along the lines of that.
I always thought they were "sealed for life" and never thought about it. Even in my automotive electrical class we were told you don't need to top them off anymore and that you will need a new one every 3 to 5 years. I did a little research and actually you CAN top them off.
I followed one of these videos on youtube of how to do it. The battery actually does have removable caps, not sure why they are marketed as sealed. The battery was really low on fluid, in one of the little holes the plates were just starting to stick out of the liquid. Took 15oz of distilled water to top it off.
I drove around a few miles to make sure it is charged fully and then shut the car off while in accessory mode. Usually the voltage will rapidly drop, this time IT DIDNT. It was acting like it was a brand new battery. This is wild to me, I have been around cars and mechanics my whole life and never knew this. Not sure how much more life I have added to it but it seemed to just magickly fix it.
Really shocked that worked and just wanted to share my experience. No clue if this is common knowledge and I am just dumb but maybe this can be helpful to someone else.