If you spill battery acid, a fresh* water
flush probably is NOT enough to completely get rid of the acid.
Most authorities recommend a slurry (paste) of baking soda*
and water, and suggest applying it liberally wherever the acid splashed.
I prefer using Dry Baking (or Washing) soda* .
Don't use a slurry, or a rag, or add water to it, before it's neutralized. Just pour on baking soda and keep pouring until the fizzing stops*
and you're left with solid mud. The baking soda will soak up and neutralize the acid. Then put on some gloves, scoop it out with a putty knife, and rinse well with fresh*
You'd be wise to wear goggles and gloves the whole time.
*  Make certain the water you use IS NOT salt water
. Salt water
and battery acid combine to make Chlorine Gas which will KILL you.
* Common Baking Soda (NaHCO3, Bicarbonate of Soda, sodium bicarbonate, or sodium hydrogen carbonate)
, or Washing
Soda (Na2CO3 , sodium carbonate, or soda ash)
can be used to neutralize battery acid.
Baking Soda is only slightly alkaline with a pH around 8.1, whereas Washing
Soda is more caustic/alkaline with a pH of 11 (with pure water being neutral at 7.0 ).
Accordingly, washing soda will consume two equivalents of acid, while baking soda will only consume one equivalent.
*  If you see any fizzing, then there is still acid left. If you do not neutralize all the acid, you may have very serious corrosion