Technologies to Detect Li-Ion Cells Thermal Failure

Several lithium-ion (Li-ion) cells undergo thermal runaway each year. Thermal runway refers to a catastrophic failure wherein all electrical and chemical energy in the cell is rapidly released as heat. Many of these events occur without apparent cause and under normal operating conditions, though research into thermal runaway blames mechanical, thermal, or electrical abuse to a cell.1

These unexplained thermal runaway events can be disastrous, ranging from explosions at Li-ion energy storage systems (ESSs) to unplugged cars exploding in their owners’ garages. Deploying robust monitoring and detection technologies in Li-ion systems is the only way to curtail events like this effectively.

Thermal Runaway Detection Systems: Legal Requirements

The Chinese government has issued strict guidelines on the function and inclusion of thermal runaway detection systems inside electric vehicles.2–4 It is mandated by such guidelines that five minutes before a hazard occurrence in the passenger compartment, any electric vehicle system must provide a warning of a thermal runaway event.

Though there have been similar safety measures for electric vehicles outlined in UN guidelines, these remain just guidelines, and there are no legal requirements within the United States around thermal runaway detection.5

To define constraints and operating conditions for thermal runaway detection, Amphenol Advanced Sensors works closely with research labs and OEMs worldwide.

Thermal Runaway Detection: Performance Requirements

There are stringent performance requirements for thermal runaway detection systems.

Passenger safety is critical in electric vehicle (EV) applications. Any thermal runaway event must be detected long before it poses any hazard to the vehicle’s inhabitants.

Stable operation must be provided by a thermal runaway detection system throughout the entire service life of a battery pack, which in automobile applications can run as high as 10-15 years.

To power auxiliary systems such as keyless entry and alarms, electric vehicles typically deploy a 12 V secondary battery system, which can markedly restrict the power draw of a thermal runaway detection system. To avoid depleting this secondary battery system, a robust thermal runaway detection system must have a very low current draw.

Electric vehicles and energy storage systems commonly use different cell geometries and configurations and one of several different battery electrochemistries. Thermal runaway detection solutions must provide reliable detection regardless of any battery system and be agnostic to all of these.  

The final factor essential for a thermal runaway detection system is the cost. Installation of a $10,000 detection system with a $5,000 battery pack is not feasible for an OEM. It is crucial instead for the detection system to be consistent with typical sensor costs in EV applications, putting them in the range of tens of dollars.

Amphenol Thermal Runaway Detection Sensors

Research into thermal runaway events has shown that gas sensors provide notable advantages in detecting the early warning signs of thermal runaway. Gas sensors also have the benefit of low cost, low power consumption, and small footprints, as well as providing rapid early detection compared to parameters such as temperature and cell voltage which respond slowly to cell venting.

The Robust Early Detection of Thermal Runaway (REDTR) system from Amphenol has been designed based on gas detection technology. It detects concentrations of flammable gases vented early during Li-ion cell failure to provide an accurate warning of impending thermal runaway within seconds.

The battery management system (BMS) is enabled by this quick response to protect vehicle occupants, engage countermeasures, and provide warnings to nearby personnel in energy storage system applications.6

From a single cell within a battery pack, REDTR provides fast and accurate detection of cell venting regardless of configuration, cell size, and electrochemistry. REDTR can be used as a standalone device or integrated directly into BMS architecture, with a compact form factor and a demonstrated performance life of up to 20 years.

To learn more about the thermal runaway detection sensor REDTR from Amphenol, contact the team today.

References and Further Reading

  1. Xiong, R., Ma, S., Li, H., Sun, F. & Li, J. Toward a Safer Battery Management System: A Critical Review on Diagnosis and Prognosis of Battery Short Circuit. iScience 23, 101010 (2020).
  2. GB 18384-2020: PDF in English. https://www.chinesestandard.net/PDF.aspx/GB18384-2020.
  3. GB 38031-2020: PDF in English. https://www.chinesestandard.net/PDF.aspx/GB38031-2020.
  4. GB 38032-2020: PDF in English. https://www.chinesestandard.net/PDF.aspx/GB38032-2020.
  5. UNECE | ECE/TRANS/180 | Global Technical Regulation on Electric Vehicle Safety (EVS). https://unece.org/fileadmin/DAM/trans/main/wp29/wp29wgs/wp29gen/wp29registry/ECE-TRANS-180a20e.pdf.
  6. Thermal Runaway Detection in Lithium Ion Batteries - Application Spotlight. https://www.amphenol-sensors.com/en/product-spotlights/3498-thermal-runaway-sensor.

This information has been sourced, reviewed and adapted from materials provided by Amphenol Advanced Sensors.

For more information on this source, please visit Amphenol Advanced Sensors.

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