Thermal runaway occurs when the battery experiences what uncontrollable condition?

• A. Overheating
• B. Low voltage
• C. Cooling failure
• D. Self-heating

Answer: (D)

Thermal runaway is driven by self-generated heat inside the battery that cannot be controlled by the cooling system. Normally, the cell produces heat and the cooling system keeps it in check. If the internal heat production accelerates and exceeds the cooling capacity, the temperature climbs. That higher temperature speeds up chemical reactions inside the cell, which in turn produce more heat, creating a self-sustaining loop. This runaway heat buildup can lead to venting, fire, or even explosion. So the uncontrollable condition is the battery's own self-heating becoming self-propagating. Overheating alone is a symptom, not the defining uncontrollable process; cooling failure is a contributing factor, and low voltage isn't the defining issue.