Thermal Runaway Propagation Testing
Thermal Runaway Propagation Test of Lithium-Ion Batteries is a critical safety evaluation performed to understand how a battery cell behaves under extreme conditions—specifically, how thermal runaway in one cell can spread (propagate) to neighboring cells in a module or pack. This test is especially important in electric vehicles (EVs), energy storage systems (ESS), and consumer electronics.
The key goal of this test is to
- Prevent propagation from a single failed cell
- Minimize the risk of fire or explosion
- Ensure safety of people and property
- Comply with industry standards
Thermal runaway propagation test simulates the failure of a single cell withing a battery module/pack to determine:
- Whether failure propagates to adjacent neighboring cells
- The speed and severity of propagation
- The effectiveness of mitigation strategies like thermal barriers, venting, cell spacing, heat sink material, passive fire protection material etc.
- The risk of fire or explosion
Various thermal runaway initiations in the cell are used:
- External heating
- Overcharging
- Nail penetration
Once thermal runaway is initiated in one of the cells, thermal propagation is monitored by measuring temperature of all the cells, time to propagation, maximum temperature of neighboring cells, energy release rate, cell venting and ruptured behavior. A video is prepared to record the events and gas composition is determined.
Standards
UL 9540A – Thermal runaway fire propagation in BESS
SAE J2464 – Abuse testing for automotive batteries
IEC 62660-2 – Safety performance of Lithium-ion cell for EVs
GB/T 31485 – Safety requirements for EV batteries (China)
AIS-048 – Indian standard for battery operated vehicles safety requirement
Sample Simulation model to replicate Thermal Runaway Propagation Testing:
Here is an example of a simple thermal model of a battery pack of 5S x 5P design (Cylindrical 18650) where, trigger cell in the center heats up from 20 deg C to 150 deg C in 20 minutes. Then let it heat and go over 400 deg C. Surrounding cells heat up due to heat transfer from the trigger cell. Thermal runaway reactions have been suppressed.
Simulation model to replicate Thermal Runaway Propagation Testing
FAQ:
1. Why is battery propagation testing important?
Because a single-cell failure in a lithium-ion battery can escalate into multi-cell fire/explosion. Propagation testing helps evaluate whether safety features can contain the failure.
2. What parameters are typically measured during testing?
- Temperature rise and maximum temperature
- Propagation delay time between cells
- Flame, smoke, and explosion intensity
- Electrical behavior (voltage/current drop patterns)
3. What’s the difference between abuse testing and propagation testing?
- Abuse testing: Puts a single cell through worst-case conditions (overcharge, crush, short, etc.) to check robustness.
- Propagation testing: Examines what happens when one cell fails and whether the failure spreads through the module/pack.
4. What design features reduce propagation?
- Thermal barriers between cells
- Fire-retardant materials
- Venting channels for gas release
- Liquid or phase-change cooling systems
- Cell spacing and mechanical isolation