What does "thermal runaway" in an aircraft battery refer to?

Thermal runaway in an aircraft battery refers to a condition where an increase in temperature leads to further increases in temperature, creating a potentially uncontrollable and hazardous situation. This occurs when the heat generated by internal resistance in the battery exceeds the heat that can be dissipated to the surroundings.

As the temperature rises, it can accelerate chemical reactions within the battery, producing additional heat and potentially leading to battery failure, fire, or explosion. This phenomenon highlights the importance of effective thermal management and monitoring systems in aviation batteries to ensure safety and functionality.

The other choices do not accurately capture the essence of thermal runaway. A decrease in battery performance over time refers to general wear and degradation, while gradual depletion of battery charge describes normal battery usage. A process to improve battery efficiency might involve modifying design or operational parameters, but it does not relate to the dangerous scenario of thermal runaway.