The presence of any small amount of potassium carbonate deposits on the top of nickel-cadmium battery cells in service indicates which condition?

• A. Excessive gassing.
• B. No special condition.
• C. Normal operation.
• D. Plate sulfation.

Answer: (C)

A small amount of potassium carbonate on the tops of nickel-cadmium cells during service is normal. The electrolyte in NiCd cells is potassium hydroxide. When the cells are charged, gas is evolved and carbon dioxide from the air can dissolve into the alkaline electrolyte. The CO2 reacts with KOH to form potassium carbonate, which can precipitate as a white crust on the cell tops. A tiny amount of this deposit is typical and indicates normal charging activity. If the deposits were heavy or accompanied by signs of heavy gassing or venting, that would suggest overcharging or other issues. Plate sulfation is not a NiCd concern—it's associated with lead-acid batteries.