The presence of any small amount of potassium carbonate deposits on the top of nickel-cadmium battery cells in service is an indication of

• A. normal operation
• B. excessive gassing
• C. plate sulfation
• D. internal short

Answer: (A)

Small potassium carbonate deposits on the tops of nickel-cadmium cells are a normal sign of venting during operation. When the cell vents, the potassium hydroxide electrolyte can react with carbon dioxide from the air to form potassium carbonate, which leaves a light crust around the vent area. Seeing a little deposit means the cell is venting as part of normal charging or operation, not that there is a fault. If the deposits were heavy, along with electrolyte loss or swelling, that would suggest excessive gassing and a charging issue. Plate sulfation relates to lead-acid batteries, and an internal short would produce other symptoms like heat and rapid discharge rather than a carbonate crust.