I dumped the acid to begin with then filled with distilled water and baking soda. That neutralizes it inside. Then I dumped that out.
I had the same muddy water on the bottom of mine also. I just kept a hose in the hole and kept dumping. It cleared up pretty good.
As of this a.m.(no charger on it last night)it was down to 11.7V. It's possible it didn't charge long enough but I have a feeling it won't hold a full charge for anything more than an hour. Oh well, I can still get my $10 core if it is not going to cooperate by this evening.