This is a good article about lithium batteries....
http://www.techlicious.com/blog/the-risk-of-exploding-lithium-ion-batteries/
What causes lithium ion batteries to fail?
Lithium ion batteries have circuitry inside to prevent overcharging and short circuits, but if this circuitry is damaged, the battery could become overheated, resulting in a process known as "thermal runaway." Thermal runaway is a chemical process where the battery generates heat, causing additional reactions that generate more heat, and so on until the entire thing finally erupts in flame. Manufacturing defects can also result in
thermal runaway.
How much heat it takes to get a battery to go into thermal runaway may vary based on the type of battery. According to Tony Olson, CEO of D2 Worldwide, which conducted the lithium ion battery test for PC Pitstop, thermal runaway can occur if the battery is heated to anywhere from
140 degrees fahrenheit up to 350 degree fahrenheit. Not standard household temperatures, obviously, but possible if the battery experiences a failure.
While the likelihood of lithium ion battery fires is still very low, two factors are increasing the risks. First is the simple fact that it's becoming far more common for us to own devices containing lithium ion batteries, including laptops, tablets, smartphones, Kindles, etc. Secondly, as manufacturers are pushing to put more and more power into these devices, the results of a failure become more pronounced.
To help avoid issues with your batteries, the Consumer Product Safety Commission recommends the following safety tips:
- Only purchase batteries and chargers directly from the manufacturer or from a manufacturer-recommended source. Buying counterfeit or poorly manufactured batteries increases the chance of having an issue.
- Do not let a loose battery come in contact with metal objects, such as coins, keys, or jewelry. Metal objects can cross the electrical connections and cause an incident if the internal protection circuitry isn't functioning correctly.
- Do not crush, puncture or put a high degree of pressure on the battery, as this can cause an internal short-circuit, resulting in overheating.
- Do not place the phone or batteries in areas that may get very hot, such as on or near a cooking surface, cooking appliance, iron, radiator or the dashboard of your car in the summer.
- If you drop your phone or laptop on a hard surface, it can potentially cause damage the battery. If you suspect damage to the battery, take it to a service center for inspection.
- If your phone gets wet, even if the device dries and operates normally, the battery contacts or circuitry could slowly corrode and pose a safety hazard.