Thermal Runaway: The Hidden Threat in Your Lithium Ion Battery. Thermal Runaway – When a battery overheats (from overcharging, damage, or defects), it can spiral into an uncontrollable chain reaction. Temperatures skyrocket, cells rupture, and flames erupt, sometimes like a flamethrower. Common Triggers Overcharging – Especially with cheap or mismatched chargers. Physical Damage – Drops, crushing, or punctures that damage internal cells. Defective or Counterfeit Batteries – Often missing vital s