1. Too much water added.
2. Battery loose in box.
3. Cracks in sealing compound due to poor sealing, or cables pulling on terminals, or due to poor quality of sealing compound, or good quality compound which has been burned.
4. Vent plugs loose.
Probable Results:
1. Upper portion of case rotted by acid.
2. Electrolyte low.
3. Plates sulphated.
4. Upper parts of separators dry.