The BATSO (Battery Safety Organization) battery test laboratory at the ITRI test institute shows a video on riskiness of unsafe batteries.
 

 
The ITRI test laboratory was designed for battery pack safety testing using the BATSO standard. It was built in Germany under the leadership of ExtraEnergy for Taiwan Industrial Technology Research Institute (ITRI). In 2007, the lab was shipped to Taiwan in order to help to check safety of battery packs in a quick and cost effective way, also in Asia.

Video of BATSO Tests
ITRI records all tests on video. This video shows, how different batteries can react on crush, external short circuit, and overcharge:

• crush test (mechanical failure): Mechanical damage of a battery can occur e.g. within an accident or when it is dropped on the ground.This can easily cause an internal short circuit which can result into an even more dangerous situation than an external circuit.
• external circuit test: Discharge of the whole battery occurs. This can result into overheating or explosion. Glowing cable connections can cause fire, too.
• overcharge test: Overcharge might occur when the battery charger doesn`t stop pumping energy into an already fully charged battery.