Metis Engineering’s Cell Guard is an advanced sensor that provides real-time insight into the condition of lithium-ion battery packs. Designed to extend pack longevity and safety, it detects cell venting, the earliest sign of catastrophic battery failure, helping to reduce the risk of fire in electric vehicles (EVs) and energy-storage systems (ESS).
Most EV battery packs already employ a battery-management system (BMS), but these systems often have limited visibility into pack health. Temperature sensors may only monitor every few cells, delaying detection of local anomalies, and voltage readings can mask early degradation as parallel cells balance the load.
While EVs are statistically safer than internal-combustion vehicles, rare thermal incidents still attract significant attention.
By supplementing the BMS with direct environmental sensing, Cell Guard provides early detection of cell venting and other instability markers, offering a more complete picture of internal pack conditions and enabling earlier intervention before a fault escalates.
Developed under ISO 26262 processes and tested to ISO 7637-2:2011, ISO 16750-2:2012, and ISO 16750-4:2010, Cell Guard is produced under automotive-grade quality systems and is already deployed in ASIL B applications by multiple OEMs and Tier 1 suppliers.
Last year, Sandia National Laboratories tested Cell Guard alongside two competing sensors, one designed for ESS applications and another for hydrogen detection in EVs (published in the Journal of the Electrochemical Society). The hydrogen sensor responded about seven minutes later, detecting the event only after thermal runaway was well underway.
“The report noted that hydrogen was not detected during the venting phase because it typically forms later, around 200 °C, during major cathode decomposition,” said Joe Holdsworth, managing director, Metis Engineering. “By contrast, Cell Guard’s VOC and combined-gas sensing provided a seven-minute warning, enough time for an electric bus to stop and safely evacuate passengers under GTR 20, the Global Technical Regulation on Electric Vehicle Safety.”
Commercial gas sensors response during over-temperature test of an 11.6 Ah pouch cell: (red) VOC; (brown) combined VOC, CO₂, H₂; and (orange) H₂. (Image: Metis Engineering)
Cell Guard transmits over a configurable CAN interface and includes a low-power monitoring mode that allows it to operate while a vehicle or energy-storage system is inactive. When a preset threshold is reached, the sensor wakes automatically, activates its 500 mA low-side drive output, and resumes full communication.
Optional hydrogen detection serves as a secondary indicator in high-VOC environments, while the integrated accelerometer records impact magnitude and duration, generating traceable data useful for resale evaluation, insurance assessment, and battery reuse.
Measurements, such as dew point, humidity, and absolute air-water content, help optimize pack cooling and prevent condensation on terminals that could cause short circuits.
Features include:
- Monitoring of VOCs, absolute and relative humidity, dew point, pressure, and air-water content
- Optional hydrogen detection and ±24 G three-axis accelerometer
- Low-power standby mode with wake-on-event capability and 500 mA low-side drive output
- Configurable CAN bus speed and address with supplied DBC file
- Compact 5-pin Molex Nano-Fit connector for straightforward integration
- Designed and assembled in the UK to ISO automotive standards
Development and link kits are available for evaluation or multi-sensor network testing. By providing early warning of thermal events, continuous environmental monitoring, and compliance with automotive standards, Cell Guard offers engineers a reliable tool for improving the safety and resilience of battery systems.
Filed Under: Sensors, Tech Spotlight, Technology News