We finally know what caused the fire of the two electric buses in Paris

Electric cars still have many detractors, even if sales continue to increase around the world. And this despite stagnation in Europe, due in particular to the reduction in government aid.

Multiple causes

If autonomy is less and less of a problem, just like the price which tends to fall, other arguments are often stated against this engine. Among them, the risk of firewhich would be higher than that for a thermal vehicle. Except that a recent study had in fact proven that this was particularly rare and that there is therefore nothing to worry about in that regard. Yes, but everything is not rosy either.

Because failures can still happen from time to time, even if they are very isolated cases. Indeed, we remember that in 2022, two RATP buses caught fire in Paris, a few days apart. If one was empty, the other carried 14 passengers, but fortunately none were injured in the fire, which completely destroyed both vehicles. These events led the transport authority to immediately withdraw all buses of the same model.

Two years later, experts have finally revealed the results of the investigation, carried out by the BEA-TTthe Land Transportation Accident Investigation Bureau. This is the same organization that recently released its conclusions on the dramatic accident involving a Tesla Model 3 in 2021 in the capital. In the document, which can be consulted online, we learn that several causes are ultimately at the origin of the two fires.

As a reminder, these vehicles, from the Bluebus brandare equipped with six battery packs, four of which are installed on the roof, due to the limited space in the floor, which is particularly low. This is the LMP chemistry (lithium – metal – polymer)which has the particularity of containing a solid polymer electrolyte. The latter helps reduce the risk of overheating, among other things. Which was clearly not enough, as the investigation report explains.

Several recommendations

In fact, several factors contributed to the fire, as is often the case with such incidents. First, this can be attributed to a production errorwhich caused a short circuit between the battery cells. The latter should have been detected by the BMS (Battery Management Systemin charge of battery management), which did not happen. That's not all, because no alert was triggeredwhich would have made it possible to warn the driver, who could have evacuated the vehicle more quickly.

But there is also another concern. You should know that fire resistance is not tested on solid electrolyte batteries, since the latter is considered non-flammable, as explained by Geoffrey Pauwels, battery expert on LinkedIn. Except that’s clearly not the case. And precisely, the investigation office now wants to remedy this problem and states seven recommendations to prevent this from happening again. These are intended for Bluebus, but not only. The first concerns early detection “ faults that could lead to fires and the reporting of appropriate alarms ».

The BEA-TT also calls for improving the passenger protection process with regard to high temperatures, the risk of batteries falling on the roof and splashes of molten metal during evacuation. Experts also ask that the recording of important data preceding the incident be maintained and transmitted regularly. They also recommend “ the continuation and facilitation of research concerning the effectiveness of the means of control to be used during events of the same type » and wish that regulations are evolving for all vehicles of this type and that the emergency services are better informed to be able to act more quickly.