What type of battery can be recharged and is commonly used in aircraft?

The correct answer is secondary cells, which are specifically designed to be rechargeable. In aircraft applications, secondary cells are preferred because they can withstand multiple charging cycles without significant degradation of their performance. This characteristic makes them practical for use in various aircraft systems where continual power supply is necessary.

Secondary cells, such as lithium-ion, nickel-cadmium, or nickel-metal hydride batteries, provide versatility and efficiency, offering high energy density and low weight—critical factors in aviation where aircraft performance depends heavily on weight and balance.

In contrast, primary cells, which cannot be recharged, are typically used in situations where long shelf life is more important than the ability to recharge, such as in emergency equipment. Lead-acid batteries are indeed a type of secondary cell, but they do not encompass all rechargeable batteries used in aircraft. Alkaline batteries, like primary cells, are not rechargeable, making them unsuitable for applications that require frequent cycling of charge and discharge.

Thus, understanding the classification of batteries helps to clarify why secondary cells are the most suitable option in aircraft settings, providing reliable energy solutions for various electrical systems.