What may result if water is added to a nickel-cadmium battery when it is not fully charged?

• A. No effect
• B. The battery becomes nonfunctional permanently
• C. Water improves capacity
• D. Excessive spewing is likely to occur during the charging cycle

Answer: (D)

Water addition during charging can push a nickel-cadmium battery into a dangerous situation because these cells generate gas as they charge. The electrolyte is alkaline, and hydrogen gas (mainly) forms at the negative plate while charging. If you add water while the battery is still charging, you increase the liquid volume inside the cell at a moment when gas pressure is building. The combination of extra liquid and rising gas pressure causes the cell to vent, often spraying electrolyte and gas out of the vents. That’s why excessive spewing is likely during the charging cycle when water has been added prematurely.

This isn’t a productive or safe practice. It doesn’t improve capacity, and it doesn’t suddenly make the battery permanently nonfunctional just from the act of adding water; it mainly causes venting, potential loss of electrolyte, and safety hazards.