Which battery type has a specific gravity that does not change significantly during charge or discharge?

The nickel-cadmium battery is known for its unique chemistry, which allows its specific gravity to remain relatively stable throughout the charge and discharge cycles. This stability is a significant characteristic because it means that users do not have to constantly monitor the electrolyte level or composition in the same way they would with other battery types, such as lead-acid batteries.

In lead-acid batteries, the specific gravity of the electrolyte changes significantly as the battery discharges and charges, reflecting the conversion of lead sulfate back to lead and lead oxide. Lithium-ion batteries do not use a liquid electrolyte and have completely different operational characteristics, focusing on intercalation rather than electrochemical reactions that involve changes in specific gravity. Alkaline batteries also do not have a significant variation in gravity but typically do not operate in the same kind of charge-discharge cycles as nickel-cadmium batteries do.

Thus, the consistent specific gravity of nickel-cadmium batteries during operation makes them distinct among battery types, highlighting their reliability and ease of maintenance in various applications.