I read your other parallel batt threads...imo, if your batt is the orig.,
I wouldn't bother going through the "check the water level" effort;
I would just get a new one and install it.

I do rec'd running a slow/low amp charge into any new battery, for a day or so:
"new" batteries are famous for having been sitting on a shelf, dying, or poorly shipped/stored.
Be sure to get a vented model, and re-attach the vent hose. Even some new batts. with "vent hole",
requires you to find that spot and sometimes poke it open with a tool, as the plastic case is often injection
molded over the "hole". It is cake to change out: just follow the DIY posts, take your time, etc. 30 mins
tops, imo.
GL,mD