Accidents and fires are typically the result of:
- Structural defects
- Technical defects
- Improper use such as; mechanical damage caused by dropping, damage to the protective casing caused by pointed objects, bending etc.
- Thermal strain caused by external heating
- Overloading (sharp temperature increase caused by the exothermic process)
- Not using the correct power connector
- Auto-ignition and severe reactions to fire, with cells exploding like small fireworks combined with rapid fire spread
Apart from improper use, danger lies in the battery cells and systems themselves
Strong currents are possible (temperature increases caused by electric arcs, short circuits etc.).
If there is a fire, poisonous and/or flammable contents can leak and form an explosive mixture.
The materials and components have a high fire load.
If the safety valve fails, batteries and battery cells can suddenly burst when they heat up or if thermal runaway occurs.
Normally caused by an electronic error or mechanical damage, thermal runaway is a typical fire scenario for Li-ion batteries and accumulators. It starts in relatively unspectacular fashion: The oxidation of the electrolyte heats the interior of the battery to around 80°C, causing gas and steam to appear in the cell. If this process is not stopped, it triggers a chain reaction. At around 120°C, the separator between the anode and cathode melts. This causes a short circuit and the thermal decomposition of the cathode. This releases oxygen which, combined with the heat energy, ignites the materials in the anode, cathode and electrolyte (mainly organic solvents, light metals and graphite). At this stage, temperatures can reach up to 1,000°C.
The potential danger of lithium ion batteries is determined by the product design and the output of the module/system itself, which is why it is important to refer to the manufacturers SDS (Safety Data Sheet) and never use non-specified recharging equipment.