Thermal runaway detection

Detect early warning signs to prevent battery fires, system failures, and safety hazards.

Thermal runaway rarely starts with heat. Long before temperatures rise, cells release gases that signal the onset of a failure event. Detecting these early warning signs gives battery management systems valuable time to respond – protecting passengers, assets, and manufacturer reputation.

Why choose our thermal runaway sensors for battery monitoring?

●Early detection of battery failure events
●Automotive-grade sensing technology
●Reliable operation in demanding environments
●Designed for long-term vehicle lifetimes

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Early detection for battery safety

The safety challenge inside every battery pack

Modern EV battery packs contain large amounts of stored energy. While advanced battery management systems significantly reduce risk, early fault detection remains one of the most critical challenges in battery safety.

Why is the detection window so short?

Thermal runaway is not a sudden event. It develops through a sequence of chemical reactions inside the cell. The earliest warning signs are often invisible, arising before any measurable increase in temperature.

Why is conventional monitoring not enough?

Voltage, current, and temperature measurements play a crucial role in battery protection. But by the time temperature sensors detect abnormal heat generation, it may be too late to stop the failure process.

Hydrogen: an early warning signal for thermal runaway

Among the gases released during the earliest stage of cell failure, it is typically hydrogen that first appears in measurable concentration – ahead of the rise in temperature that conventional monitoring detects. That makes it a practical target for early gas sensing before the failure becomes self-sustaining.

How early detection supports BMS intervention

Detecting battery degradation at the earliest opportunity enables the BMS to initiate protective actions such as cooling, power limitation, system warnings, or module isolation before a critical safety event occurs.

Want more detailed information?

Download our latest article on EV safety for free. Our expert Martin Ebner provides an in-depth understanding of safety technology and the importance of sensor technology.

Article on EV safety

Want more detailed information?

Download our latest article on EV safety for free. Our expert Martin Ebner provides an in-depth understanding of safety technology and the importance of sensor technology.

Article on EV safety

Three requirements for reliable battery safety monitoring

High confidence, zero false alarms

Battery systems operate in highly dynamic environments. Detection methods have to accurately identify genuine failure events while avoiding false alarms caused by normal operating conditions, which erode trust in the system and can trigger unnecessary interventions.

Long-term signal stability

Automotive platforms are expected to run reliably for more than a decade. Safety-critical sensing has to maintain performance levels despite aging, environmental stress, and changing operating conditions, throughout the vehicle’s full service life.

Reliance under real-world conditions

Battery sensors have to withstand temperature fluctuations, vibration, humidity, and contaminants. Credible safety decisions rely on measurements that are just as accurate and repeatable under these demanding conditions as they are in the lab.

Hydrogen sensor options for thermal runaway detection

Sensirion offers STC42A and SGP42A as alternative H₂-sensing technologies for battery monitoring. The right choice for you will depend on your pack architecture, response-time requirements, and integration constraints.

Comparison of response time, package size, and integration requirements

Specification	STC42A	SGP42A
Sensing principle	Thermal conductivity (TC)	Metal oxide (MOx)
Measured gas	Hydrogen (H₂)	Hydrogen (H₂)
H₂ measurement range	0 to 40 vol% in clean air	Contact Sensirion
Specified sensor response	1 s, τ63	<4 s
Operating temperature	-40 to 105 °C	Contact Sensirion
Package size	3.5 × 3 × 1 mm	2.44 × 2.44 × 0.85 mm
Designed lifetime	DS	DS
Automotive qualification	AEC-Q100	AEC-Q100

Complementary smoke detection for battery safety systems

Particle-based smoke detection can be included alongside H₂ sensing as part of a broader monitoring concept.

Discuss with your expert

Sensirion supports component selection and design-in guidance. The system integrator retains control over application-specific details such as placement, thresholds, diagnostics, and the use of individual signals; no single sensor can ensure compliance at the pack or vehicle level in isolation. Ultimate validation takes a complete system design in line with applicable market requirements.

On-demand webinar

Advancing safety on the road: Detecting thermal runaway in battery electric vehicles

Martin Ebner, Business Development Manager

Watch now

Further applications

Electrolyte leakage detection

Lithium-ion batteries are hermetically sealed during production and are designed to remain sealed throughout a vehicle's lifespan. Electrolyte leakage into the battery pack is an early sign of a fault. Detecting this allows for preventive maintenance, avoiding potential failure. Sensirion's SGP4x sensors, based on metal oxide technology, are ideal for this application.

Product: SGP4x

Water ingress detection

Battery packs are designed to be watertight, but prolonged use can compromise seal integrity, leading to water ingress from the environment or cooling system leaks. This can cause insulation faults, short circuits, electrolysis, and corrosion. Detecting water ingress early is crucial for taking corrective action to avoid harm. Sensirion’s SHT4xA sensors, based on our proven CMOSense technology, are perfect for this application.

Product: SHT4xA

Smoke detection

Smoke from fire or smoldering is a strong indicator of safety risks. Our ultra-compact SPS6x single-chip sensors are ideal for detecting smoke in confined spaces like battery packs.

Product: SPS6x

Hydrogen leakage detection for FCEV

Hydrogen-powered fuel cell electric vehicles are seen as eco-friendly alternatives to internal combustion engines. Due to hydrogen's flammability, detecting leaks is critical for safety. Our STC4xA thermal conductivity sensors are ideal for this purpose.

Product: STC42A