What if the lithium battery catches fire？ Fire precautions for lithium batteries

According to the Local Fire Service of Australia (CFA), on July.30 2021 a fire broke out at an electrical storage facility in Moorabool, Australia, a 13-tonne Set of Tesla Megapack batteries caught fire and more than 30 fire engines arrived at the scene to take part in the operation, which took 150 firefighters four days to contain until August 3. Battery fire is an extreme safety accident, large to energy storage power station, small to electronic toys, battery fire is not necessarily the cause of the battery (core), may also be caused by electrical failure of the battery system. What if the battery catches fire?

The essence of lithium battery fire is that the heat in the battery is not released according to the design intention, causing the internal and external combustion material to catch fire after ignition, the main causes are external short circuit, external high temperature and internal short circuit.

1. internal short circuit: due to the abuse of batteries, such as overcharged, battery production process dust and other long-term use of dust and dust to produce a micro-short circuit, the release of electrical energy led to temperature rise, temperature rise brought about by the material chemical reaction expanded the short circuit path, forming a larger short-circuit current, resulting in out-of-control heat fire.

2. external short circuit: take electric vehicle as an example, in the extreme case, short circuit point over the vehicle fuse, while the battery management system failure, a longer period of time external short circuit will generally lead to the connection weak point in the circuit burned, thus causing the external short circuit fire.

3. external high temperature: due to the characteristics of lithium battery structure, high temperature core internal material decomposition reaction, electrolyte decomposition will also react with positive and negative poles, core diaphragm will melt and decompose, a variety of reactions lead to a large amount of heat generation. The melting of the diaphragm causes the internal short circuit, the core explosion-proof film to rupture, the electrolyte ejection, resulting in burning fire.

Analyzing the causes of battery fires, when lithium batteries need to be put out to fight fires, let’s look at Tesla’s recommendations

1, if encountered a small fire, the flame did not spread to the high-pressure battery part, can use carbon dioxide or ABC dry powder fire extinguisher fire extinguisher.

2, in a thorough inspection of the fire, do not come into contact with any high-voltage components, always use insulation tools to check.

3, if the high voltage battery in the fire bending, twisting, damage, in short, become not like, or suspect that the battery problem. Then the water consumption when extinguishing the fire should not be too small, fire water should be sufficient.

4, Battery fire may take 24 hours to completely extinguish. Using a thermal camera ensures that the high voltage battery is completely cooled before the accident is completely complete. If you do not have a thermal camera, you must monitor the battery for re-ignition. Smoke indicates that the battery is still hot and monitoring will remain in control until at least an hour after the battery is no longer smoking.

According to the U.S. Fire Protection Agency, electric vehicles can catch fire “over 2,760 degrees Celsius” and “the use of water or foam can cause violent flames, as water molecules break down into explosive hydrogen and oxygen.” So it’s not safe to put out a small amount of water, and an electric car alone requires dozens of tons of water.

Simply put, lithium battery fire fighting uses a lot of water to cool the battery, it takes a long time and patience, cooling is the key.

Electrical safety monitoring subsystem

Energy storage systems and fire protection systems are not separate units, but should become a centralized and intelligent whole, improving the system flexibility and safety of fire protection systems is fundamental to ensuring the commercialization of energy storage systems. In the future, the new energy storage mode and fire protection plan will increase, and the energy storage fire protection system will gradually tend to be centralized and intelligent.