Sulphation

Checking Electrolyte Level:

A battery (with specific gravity less than 1.100) will completely discharge when left unattended for a long period of time.This may result in sulphation on the cell plates.
A sulphated battery may sometimes be brought into service by means of a slow charge, 12 hours or more. A capacity test should be run after the battery is charged to ensure the battery is not damaged.