Fire fighting for lithium battery fires

There are different views on the use of water as an extinguishing agent. Because lithium is very reactive, some people advise against bringing it into contact with water. However, recent research suggests that larger amounts of water are able to contain and effectively fight lithium fires. The explanation given here includes the cooling effect, which slows down the reaction of the cells. Large batteries, for example from burning electric cars, regularly present fire brigades with an enormous challenge, however. This can be explained by looking at the structure of a traction battery:

A large traction battery consists of many smaller cells that are connected together. If a single cell heats up, in the worst case in the middle of the module, the neighbouring cells will also inevitably heat up. This results in a chain reaction that leads to a considerably higher release of energy. If the chain reaction was triggered at the centre of the battery, it is almost impossible to reach it with an extinguishing agent, e.g. water, and thus stop or contain the reaction. If you now try to cool the module, the water only reaches the outer layers or the battery housing. The situation is different for smaller modules where fewer cells are used. Here, external cooling usually has a direct effect on the reacting cells.

In the summer of 2019, the VdS published leaflet 3856 "Sprinkler protection of lithium batteries". For the first time a differentiation was made by energy content per storage unit and the risk was classified according to the following table:

The recommendation is to store a maximum of 50 kWh per storage unit (e.g. Euro pallet). This is equivalent to Hazard Level II. The sprinkler system must be designed in accordance with VdS CEA 4001. Tests by the American property insurer FM-Global and the German Insurance Association (GDV) have shown that the spread of lithium battery fires in high racks can be prevented by a targeted sprinkler system. However, the findings from the tests are only valid for small lithium batteries packed in cardboard boxes. The sprinkling of large battery units is nevertheless advisable, as although the fire is not usually extinguished at the individual battery, the spread to neighbouring batteries can be slowed, if not prevented.

However, a significantly higher amount of water is needed to fight the fire than in conventional fires. In order to accelerate success and, if necessary, to reduce the amount of water required as well, various additives can be added to the extinguishing water. If there is a reaction, there is a risk of hazardous substances such as hydrochloric or hydrofluoric acids being released from inside the cell. This may appear in the form of vapour for example, which could injure workers through skin contact or inhalation. When a fire is extinguished the extinguishing water can dilute the acids, they can seep into the ground (if there is no suitable containment device) and cause environmental damage.

Another extinguishing possibility for lithium fires is aerosol extinguishing technology. This is a permanently operational technical system that is used to suppress the fire until the fire brigade arrives to finally extinguish the fire. The extinguishing technology operates according to EN 15276-10, without addition of water. The extinguishing generator effectively interrupts the chemical combustion process within 4.5 to 15 seconds (depending on model) when the temperature rises. This technology is environmentally friendly and human-compatible (not harmful to health, does not displace oxygen). Among other things, it is listed as an official "HALON replacement extinguishing agent" by the United States Environmental Protection Agency (U.S.EPA). Due to the low weight/installation volume and the fact that no piping is required, simple and quick installation is possible. Investment and follow-on costs also remain low, as aerosol extinguishing technology is maintenance-free and has a long product life.