Thermal Runaway Collars: Delivering Safety and Peace of Mind to Electric Vehicle Drivers

Electric vehicles are growing in popularity but there are some legitimate safety concerns regarding the lithium-ion batteries they contain. A battery cell only needs to reach an internal temperature of 200 degrees Fahrenheit to see oxidation begin to occur. When this happens, the fuels contained in the battery react with the oxidizer and release extremely hot jet fire flames. These flames can rapidly raise the temperature of neighboring battery cells causing a perilous chain reaction.

Electric car manufacturers typically equip their vehicles with Battery Management Systems consisting of temperature sensors, cooling fans, and insulating layers between cells, and these systems do pretty well to temper the risk involved in operating an electric vehicle. But their success rate is not perfect. So, what happens when the battery management system encounters a problem and fails to turn on the cooling fans in time? That’s where ACS comes in.

ACS has, for decades, been the global leader in Pyrotechnic Airbag Inflator Filters. These filters work by containing the harmful particles and burning metals released by the chemical reaction that inflates an airbag. The rapidly released gas contains about 60% burning metal. It is pivotal that the filter completely contains the harmful elements without slowing down the flow of gas into the airbag. ACS has adapted these airbag filter technologies to function as Thermal Runaway Collars in electric vehicles.

Our Thermal Runaway Collars act as a failsafe in the event of thermal runaway by muffling the released flames without causing any potentially calamitous backpressure. Our filters are designed so that the backpressure does not exceed the pressure inside the bank of cells and thus, compounding chain reactions don’t occur. The filters allow the resultant internal combustion pressures to be far below the maximum design backpressure and the failure point of the bank of battery cells. This way the filter is not the controlling orifice, rather it is an optimized flame arrestor for any bank of EV cells.

Thermal Runaway Collars on the market today typically consist of small, crimped mesh caps on each battery cell. These filters reduce emitted flames but do not eliminate them. The technology used greatly resembles early versions of the Pyrotechnic Inflator Filters ACS produced decades ago, before inventing Variable Expanded Metal™ radial filters. VEM filters employ multiple layers of expanded metal to create a flow path that has been proven to be the most effective system available for remedying airbag risk without slowing inflation. We have adapted this technology to fit on a lithium-ion battery cell to completely eliminate emitted jet flames and provide electric car drivers with the same peace of mind that our pyrotechnic airbag inflator filters always have.