During charging of a nickel-cadmium aircraft battery, what is the effect of gassing on the electrolyte?

• A. Water is consumed during charging
• B. Water is produced during charging
• C. Water levels are unaffected
• D. The electrolyte becomes more acidic

Answer: (A)

Gassing happens when the electrolyte in a nickel-cadmium battery is electrolyzed during charging. Water molecules in the potassium hydroxide electrolyte are split to form hydrogen and oxygen gases. This process uses up water from the electrolyte, so the water content drops as charging continues (especially if overcharged or charged at a high rate). As a result, the electrolyte becomes more concentrated and remains highly alkaline. Water is not produced, the water level isn’t unchanged, and the electrolyte doesn’t become more acidic—its alkalinity remains, and with water loss it becomes more concentrated rather than acidified.