New Sensor Technology Could Save People From EV Fires

Lithium-ion batteries provide high energy density and fast charge/discharge rates, which is why they are so popular today. The same factors that make lithium-ion batteries ideal for smartphones and laptops also make them optimal for electric vehicles. But lithium-ion batteries are susceptible to thermal runaway, which is a serious concern for the massive battery packs used in electric cars. New sensor technology from Amphenol provides an early warning of thermal runaway and could save lives.

A few minutes on YouTube are all you need to find video examples of lithium-ion thermal runaway. Most of those videos show smartphones bursting into flames. That makes sense, because almost every adult in the developed world owns a smartphone. Those fires often result in serious injury, but that is trivial compared to the danger of thermal runaway in an electric car When the batteries in an occupied Tesla catch fire, there is a high risk of death. Amphenol's sensor technology, and sensors from other companies that are sure to come, will reduce that risk.

Thermal runaway happens when one failing cell in a lithium-ion battery experiences oxidation and reduction reactions. That causes the cell to rupture and release gases that are hazardous and flammable. Even if those gases don't catch fire, they can cause neighboring cells in the battery to rupture. The result in a chain reaction and all the battery's cells soon follow suit. The released gases are a direct hazard, but they are also very flammable. In the presence of a suitable ignition source, they produce a hot and dangerous fire.

Current battery protection technology relies on monitoring current, voltage, and temperature. Those are dependable for detecting when a battery has already experienced catastrophic failure, but they don’t always provide an early warning. A battery's cell could rupture without affecting the current, voltage, or temperature by a detectable amount beyond a reasonable tolerance. This means that your first indication of a problem could be a fire.

The solution, as Amphenol sees it, is to look for the gases that lithium-ion cells emit when they first rupture. There are two important gases that they can detect: CO2 and hydrogen. They can detect CO2 using non-dispersive infrared spectroscopy sensing. They can detect hydrogen using thermal conductivity sensors. Put the two together and you get Robust Early Detection of Thermal Runaway (REDTR).

Amphenol's REDTR solutions, which recently hit the market, come in several forms. Engineers can place self-contained devices inside of existing battery compartments or they can install packages onto battery management system (BMS) PCBs. In testing, Amphenol's partners found that REDTR products provided fast and consistent detection of the cell venting that correlates with the early stages of lithium-ion thermal runaway. There is little doubt that technology like Amphenol's REDTR will soon be common in electric vehicles.