Batteries in electric vehicles can fail quickly, sometimes catching fire without much warning. Sandia National Laboratories is working to detect these failures early and provide passengers with appropriate warnings.

While electric vehicles have systems to detect lithium-ion battery performance problems, these systems do not address the immediate safety issues.

“The nature of battery fires can vary greatly depending on the mode of failure. Some batteries self-heat for hours, while others are abrupt and aggressive,” said Alex Bates, a member of Sandia’s battery safety group.

“The battery starts to heat up uncontrollably, eventually resulting in a fire.”

Current measurements in battery management systems capture temperature and voltage, but these are late indicators of safety issues.

This means that a warning may not appear until it is too late, especially when the battery is about to catch fire or is already on fire.

“We’re focused on extending the warning time,” said Loraine Torres-Castro, Sandia’s battery safety manager.

“Our goal is for the diagnostic system to provide an early warning, allowing time to safely park and exit the vehicle.” She added that the ultimate goal is to integrate this warning system into the car’s dashboard.

Electrochemical, gas sensor

Talking to IETorres-Castro said Sandia’s Battery Abuse Test Lab tests batteries used in various applications for performance and safety.

Work is focused on extending warning times for battery failures. The team tested commercially available diagnostics on single-cell packs and batteries, focusing on methods such as rapid electrochemical impedance spectroscopy (EIS) and gas detection.

Fast EIS differs from traditional battery management methods in measuring impedance across frequencies in near real time.

This approach can detect subtle changes in cell impedance before traditional temperature and voltage-based indicators show any sign of failure.

Unlike conventional EIS, which can be slow and often Impeccable for dynamic, in-operando monitoring, fast EIS is designed to operate at a faster scale, making it more suitable for real-time on-board diagnostics.

On the other hand, the team is also testing sensors for emissions of volatile organic compounds (VOCs) and hydrogen (H2), which can provide additional markers of failure. VOC sensors, for example, detect off-gassing in the early stages of battery degradation (often before visible off-gas is seen).

Fast detection of EV battery fire

Testing focuses on evaluating the effectiveness of technologies rather than the specifics of their integration.

However, the goal is for these diagnostic tools to be compact and lightweight for integration into an electric vehicle’s battery management system.

Unlike traditional diagnoses which is based In terms of voltage and temperature monitoring, fast EIS can identify internal battery faults before they become visible symptoms.

This ability to provide an earlier warning allows for timely intervention, particularly in the prevention of thermal runaway.

In addition, fast EIS can help assess battery health and detect problems such as capacity degradation and internal short circuits.

The team is currently rigorously testing these technologies to ensure reliability and determine the effectiveness of the methods under various conditions, such as overtemperature and overload.

There is still work to be done before this technology can be implemented in electric vehicles. As a next step, Sandia will have battery packs from electric vehicles in the lab. The cells will be tested at different scales to check the limitations of current diagnostics on the market.