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Fire damage

Overview

A number of fires at Li-Ion BESS facilities have occurred, in some cases resulting in injury to fire crews
This has focused attention on the need to improve the design, quality control, fire safety systems and operational procedures for Li-Ion projects in particular
Fires are usually caused by thermal runaway, when damage to or abuse of an individual cell (including excessive ambient heat) causes it to heat up uncontrollably and trigger the same in neighboring cells
This is typically accompanied by the release of flammable gases, such as hydrogen. The ability of the system to vent such gases is important and guidelines such as NFPA 68 and NFPA 69 provide helpful design advice in this respect
Fires may also be caused by faults on wiring or control systems which are not directly related to a defect on the batteries themselves, or on the inverters and transformers which are often located within or near to battery enclosures
Water based fire suppressant systems are the most effective at slowing thermal runaway but if triggered by mistake can cause widespread damage to non-faulty equipment
Clean agent fire suppressants extinguish normal electrical fires without causing wider damage, but do not stop thermal runaway
The onus is on manufacturers to prove their products' resilience to thermal runaway damage by carrying out fire testing, for example in accordance with UL9540A

Avoiding fires requires adequate control at the design stage:

Compliance with a recognized fire code
Large scale fire testing of battery cells and modules by the Original Equipment Manufacturer (OEM) to establish how they behave in the event of thermal runaway. UL 9540A is a universally recognized test method for this. However it cannot recreate all real-life scenarios for a thermal runaway event
Allowing sufficient distance between modules to stop fire propagating between units (the standard requirement is three feet according to the NFPA 855 and ICC IFC guidelines but larger distances reduce the risk)
Early gas/smoke detection systems and adequate dry agent or water-based fire suppressant systems
Indoor BESS facilities must have adequate fire walls between batteries and inverters/transformers
Condition monitoring at cell, module and unit level to detect abnormal currents or voltages, plus surge protection and fuses to disconnect power if these occur
During operations, the Heating Ventilation and Air Conditioning (HVAC) system must maintain correct operating temperature within the BESS
Aggressive cycling (charging and discharging) of the cells can also result in failure, or reduced battery life

What's next: Corrosion damage