Batteries power countless devices, making them integral to modern life. While generally safe, under certain conditions, a battery can experience a rapid and uncontrolled release of energy, often involving fire, smoke, or a physical rupture. This event, often called an “explosion,” is a safety concern due to the widespread presence of batteries in homes, vehicles, and personal electronics. Understanding the factors that lead to such incidents is important for safe usage.
Understanding Battery Failure
A primary mechanism behind battery failure at elevated temperatures is known as thermal runaway. This is a self-accelerating cycle where an increase in temperature within a battery cell causes chemical reactions to speed up, which in turn generates more heat. If this heat cannot dissipate quickly enough, the temperature continues to rise uncontrollably, leading to further degradation and a potential thermal event.
Several factors can initiate or accelerate this heat buildup. Internal short circuits, often caused by physical damage like punctures or crushing, or by manufacturing defects, can lead to a rapid discharge of energy and intense localized heating. Overcharging a battery beyond its designed capacity can also generate excessive heat and stress internal components, pushing the battery towards thermal runaway. External heat sources or prolonged exposure to high ambient temperatures can also trigger this process.
Temperature Thresholds for Common Batteries
Different battery chemistries exhibit varying temperature thresholds for dangerous thermal events. For lithium-ion batteries, thermal reactions can begin around 80°C (176°F), with runaway typically occurring between 140°C (284°F) and 850°C (1562°F). During thermal runaway, the internal temperature of a lithium-ion cell can reach over 600°C (1112°F) quickly.
Nickel-Metal Hydride (NiMH) batteries are generally more stable than lithium-ion cells, but they can still overheat, particularly during overcharging. Excessive heat in NiMH batteries can lead to electrolyte leakage, internal pressure buildup, and in severe cases, bursting or fire. Charging them above their rated temperature can cause damage or venting.
Lead-acid batteries are also susceptible to thermal runaway, especially when subjected to high ambient temperatures or overcharging. For every 10°C (18°F) increase in temperature above 25°C (77°F), the lifespan of a lead-acid battery can be halved due to accelerated chemical reactions and increased corrosion. Though less prone to explosions than lithium-ion batteries, severe overheating can still result in melting, fire, or rupture.
Safe Battery Handling and Storage
Preventing batteries from reaching dangerous temperatures involves specific handling and storage practices. Always use the charger designed for your battery and device, and avoid overcharging, as this is a common cause of excessive heat generation. Unplugging once fully charged remains a good practice.
Storing batteries in cool, dry environments away from direct sunlight or heat sources is important. For lithium-ion batteries, an ideal storage temperature range is typically between 10°C and 25°C (50°F and 77°F). Physical damage, such as puncturing, crushing, or dropping, can compromise a battery’s internal structure and lead to short circuits, so protecting batteries from impact is important. Avoid using or storing batteries in extreme hot or cold environments, as this impacts battery health and safety. Choosing reputable battery brands and products also helps ensure manufacturing quality and integrated safety controls.
Responding to Overheating Batteries
If a battery shows signs of overheating, such as swelling, hissing sounds, smoke, an unusual odor, or excessive heat to the touch, immediate action is necessary. If connected to a power source, disconnect it immediately. Move the device or battery to a non-flammable surface, away from combustible materials, using a long-handled tool if possible to avoid direct contact.
For lithium-ion battery incidents, water is effective for cooling and can help prevent reignition; submerging the battery in a sturdy container of water for at least 24 hours is recommended. While general-purpose fire extinguishers may suppress flames, specialized Class D fire extinguishers or those containing Aqueous Vermiculite Dispersion (AVD) agents are designed for metal fires and lithium battery fires, offering better cooling and suppression. In the event of a significant fire or explosion, evacuating the area and immediately contacting emergency services is essential.