The BTC-500 (Battery Testing Calorimeter) is a floor-standing adiabatic calorimeter for the safe testing of thermal, electrical, and mechanical stress (abuse) tests on larger battery cells, and small modules. Evaluation of these tests facilitates the assessment of the safety performance of battery cells, enables the battery’s safe operating limits to be defined, and facilitates research and development into the mechanisms of thermal runaway and thermal propagation.

• Characterizing differences in cell performance
• Defining safe operating limits
• Exploring thermal runaways and thermal propagation

Features and Options

Type of Test

• Thermal stress: the BTC-500 enables a cell to be subjected to thermal stress under adiabatic conditions, allowing for assessment of its thermal stability and the characterization of thermal runaway events.
• Electrical stress: Full integration with charge-discharge units supports testing of overcharging and discharging rates. External short circuits can also be applied. Resultant thermal runaway events can be characterized under “worst-case”, adiabatic conditions.
• Mechanical stress: the BTC-500 can be equipped to perform nail penetration puncture tests, and allows for the characterization of the subsequent thermal runaway.
  • High data rate acquisition, up to 10,000 Hz is available for characterizing extremely fast reactions. 100 Hz data acquisition and unique tests are available for compliance with GB/T 36276-2018
  • Additional capabilities to aid further mechanistic understanding of thermal propagation and thermal runaway include:
    • Automated gas sampling for vent gas analysis.
    • Triggering a cell at a specific position within a module to undergo thermal runaway.
    • Integrated video camera to record changes to the test sample.
    • Thermal mapping (multipoint temperature measurement) of a sample.

Battery/Sample Size

• Cylindrical cells (upwards from 18650), prismatic cells, pouch cells, and small modules.
• Chamber internal size – 500 mm diameter / 500 mm tall.

Temperature Control

• Ambient to 500 °C.
• Optional: sub-ambient temperatures starting from -40 °C

Intelligent Software Control and Analysis

• Control software enables regular data logging, multi-step recipes, parameter control, and feedback loops.

Safety Features

• Automatic, user-configurable event detection and shutdown procedures, to ensure user safety
• Containment vessel designed to retain fragments and fumes should a sample decompose
• N₂ purge for when operating under sub-ambient conditions, or for the safe purging of hazardous gases after a thermal runaway
• Automatic hardware and software fail-safes are installed on every system

Applications

Safety Testing

Define safe operating limits:

• It is essential to identify the safe operating limits of battery cells, modules, and packs in order to avert the risk of thermal runaway, and the potentially catastrophic consequences to which it could lead. Therefore, batteries need to be subjected to mechanical, electrical, and thermal stresses in order to define their safe operating limits.
  • Thermal stability data from thermal stress tests can help define the safe working temperature of the battery
  • The evaluation of over-charging and discharging rates allows the maximum safe voltage and maximum safe current to be determined
  • The consequences of mechanical stresses and external short circuits (ESC) can be evaluated

Exploring thermal runaways and thermal propagation

• In general, most extreme conditions can result in thermal stress on the battery cell, which can lead to a thermal runaway. Therefore, for the development of safe batteries, it is essential to understand the mechanism of the thermal runaway in a cell, and how it propagates within a module or pack so that appropriate mitigation strategies can be implemented.
  The data obtained from the stress tests performed in the BTC-130 and the BTC-500 can be used to model a cell’s predicted thermal behavior. Successive onset temperatures of decomposition of components within the cell can be detected, and the resultant heat released determined. This can help to facilitate a mechanistic understanding of the thermal runaway within the cell. Further insight can also be derived from the external analysis of the composition of any evolved gases collected.
  The BTC-500 also enables the triggering of a cell at a specific position within a module to undergo a thermal runaway with a mechanical- or electrical-induced short circuit, while the integrated camera will visually capture the event unfolding. The induced thermal runaway allows the risk of thermal propagation to be evaluated, the magnitude of the thermal event to be characterized, and appropriate mitigation measures to be implemented within the module design to ensure heat dissipation is greater than heat generation.

Performance Testing

Characterize differences in cell performance

• The BTC-130 and BTC-500 can be used to characterize the cell performance under more extreme operating conditions. The absolute limit of safe, repeated use can be assessed with the automated cycling of the battery cell until the heat generated by its discharge causes the onset of self-heating. Similarly, puncture tests provide an indication of the structural stability of the cell. The resulting thermal event can also be captured on camera on the BTC-500. These tests enable the safety performance of the cells to be compared.

Find out more in our guide Solutions in Battery Technology Testing: Hazard screening, safety testing and performance characterization