Diagram of thermal runaway


Thermal runaway refers to a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. Typical causes of thermal runaway events can be forced discharge of electrodes, which are insufficiently wetted by electrolyte, or excessive discharge currents, as in an internal or external short circuit.

In other words, "thermal runaway" describes a process which is accelerated by increased temperature, in turn releasing energy that further increases temperature. In chemistry (and chemical engineering), this risk is associated with strongly exothermic reactions that are accelerated by temperature rise. In electrical engineering, thermal runaway is typically associated with increased current flow and power dissipation, although exothermic chemical reactions can also occur under some conditions.


When handled improperly, or if manufactured defectively, some rechargeable batteries can experience thermal runaway resulting in overheating. Sealed cells will sometimes explode violently if safety vents are overwhelmed or nonfunctional. Especially prone to thermal runaway are lithium-ion batteries. Reports of exploding cellphones occasionally appear in newspapers. In 2006, batteries from Apple, HP, Toshiba, Lenovo, Dell and other notebook manufacturers were recalled because of fire and explosions.[1][2][3][4] The Pipeline and Hazardous Materials Safety Administration (PHMSA) of the U.S. Department of Transportation has established regulations regarding the carrying of certain types of batteries on airplanes because of their instability in certain situations. This action was partially inspired by a cargo bay fire on a UPS airplane.[5] One of the possible solutions is in using safer and less reactive anode (lithium titanates) and cathode (lithium iron phoshate) materials together with non-flammable electrolytes based on ionic liquids. In lithium-ion cells, thermal runaway can be triggered by internal short circuits, physical damage, or overheating of the cell (typically from exposure to temperatures above 60°C). The result of thermal runaway in a lithium-ion cell is typically a fire or explosion.





APC Smart-UPS 700 Issues - Battery Thermal Runnaway

C Smart-UPS 700 Issues - Battery Thermal Runnaway