Stellantis patents ‘EV exhaust system’ to prevent thermal runaway

It sounds like a ‘contradictio in terminis,’ an exhaust system for fully electric vehicles that are supposed to have no emissions at all. Still, Stellantis Group, parent company to Peugeot, Jeep, and Fiat, among others, has filed a patent with the United States Patent and Trademark Office (USPTO) for a system that would evacuate dangerous gases in the ‘unlikely event’ of a battery fire.

Rechargeable batteries, especially lithium-ion ones used in consumer electronics or electric cars today, can experience what engineers call a ‘thermal runaway.’ Damages or charging defects can result in overheating and the release of flammable gases that ignite and cause a domino effect and a fire or even explosion that is difficult to put out.

Removing dangerous gases

Green Car Reports was the first to point at the patent published by USPTO. Stellantis argues that removing those gases could prevent thermal runaway from escalating into fires and release pressure from the battery pack.

The gases that can be formed are far from harmless, including highly flammable hydrogen and methane, ethane, ethylene, acetylene, propane, cyclopropane, and butane.

EV makers do everything today to avoid such a scenario, but think about the occasional newspaper reports of exploding cell phones or e-bike batteries. Or why do you think most airlines forbid transporting certain types of batteries in the cargo bay on planes because of their instability in certain situations?

Hard to extinguish

EV fires get a lot of media coverage because they can be spectacular and take hours to extinguish. They must be dropped in a water container to prevent reigniting time after time. Still, several studies have concluded that EVs are far less likely to combust than cars with internal combustion engines.

The most likely scenario for an EV battery to catch fire is when cells are damaged or pierced in an accident and the highly flammable electrolyte liquid used in today’s lithium-ion batteries leaks. This risk would be far less with batteries of the future generation, using a solid-state electrolyte instead. Or when something goes wrong during charging.

Preventing fatalities

Today, EV makers do everything to prevent these fatalities, including advanced thermal management and vast amounts of crash protection to protect the battery pack from deformation. The packs are also wrapped by liquid cooling systems and monitored at the module or cell level to cut off a defective part instantaneously.

However, Stellantis wants to be prepared for the worst by using an exhaust system and mitigating the effects of a battery fire causing a thermal runaway in ‘the unlikely case.’

As Green Car Reports remarks, Stellantis’ four new modular STLA platforms are designed to accommodate combustion engines, their exhaust systems, and all-electric powertrains, so there’s room for the necessary plumbing.

The patent describes not only how the dangerous gases are evacuated into the open air but also how they are treated and ‘scrubbed’ in a way of speaking to become less harmful.

Stellantis mentions in the filing: “a plurality of treatment zones for chemically treating the flow of gases to eliminate or at least reduce the number of various chemical species from the flow.” It is somewhat similar to a catalytic converter in today’s ICE exhausts.

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