Accelerating Rate Calorimeter (ARC) for Battery Testing
Accelerating Rate Calorimeter (ARC®) is a specialized calorimeter used to study the thermal stability and runaway behavior of chemicals and batteries (lithium-ion, sodium-ion). Primarily it was developed to measure thermal behavior of chemicals but now it is commonly used to evaluate the thermal safety of batteries.
ARC provides pressure and temperature response when sample is subjected to heat. It is used to obtain thermodynamic properties of chemical reactions:
- Number of exotherms
- Onset temperature of exotherm
- Temperature and pressure rise rate
- Total pressure and volume of gases
- Vent opening pressure and temperature
- Adiabatic temperature rise
- Heat of reaction (Total heat generated)
Exotherm rates as low as 0.02°C/min can be detected under heat-wait-search heating mode, or as low as 0.005°C/min for iso-aging mode. The significant advantage that the ARC offers over other similar techniques is exothermic onset detectability at 0.02°C/min along with simultaneous pressure measurement.
Standards / References:
ASTM E1981 “Assessing Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry”
Equipment used:
- CSI ARC 2000
- TIAX (Netzsch Instrument) ARC 254
CSI ARC 2000
TIAX/ Netzsch ARC 254
Example Test:
A typical cylindrical 21700 Li-ion cell was tested for thermal characterization using CSI ARC as open test with continuous cell voltage measurement. A plot of cell temperature and voltage vs. time is shown below and test results are reported below in the table.
Cell Temp & Voltage vs. Time plot
Temperature Rise rate vs. Temperature
Table 1: ARC Test result
| Cell Type | Wt. Loss | Onset T of Exotherm* | Max. Holder T | Max. Cell T | Heat of Reaction | Max. Cell dT/dt | Max. Cell Holder dT/dt | Cell V Drop T | Cell T at 15 °C/min |
|---|---|---|---|---|---|---|---|---|---|
| Typical | % | °C | °C | °C | kJ | °C/min | °C/min | °C | °C |
| 21700 | 66 | 90 | 434 | 1352 | 81 | 29,292 | 627 | 106.2 | 171.4 |
FAQ:
1. How does Accelerating Rate Calorimeter (ARC) work?
- Sample placement: The test cell (battery, chemical, powder, etc.) is placed inside a sealed chamber of the ARC.
- Heating: The ARC slowly heats the sample in small temperature steps (e.g., 5–10 °C).
- Heat–wait–search mode: Heat a step → Wait to stabilize → Search for self-heating.
- If no self-heating, continue heating.
- If self-heating is detected, the ARC switches to adiabatic tracking mode.
- Adiabatic tracking: The chamber follows the sample’s temperature rise, ensuring no heat escapes, so the ARC records the true self-heating rate.
- Runaway capture: If thermal runaway occurs, the ARC measures temperature, pressure, and heat release rate
2. Is ARC a safety certification test, are there any typical criteria for success?
No. ARC is not a compliance/certification test, but a diagnostic / research tool and one of the option tool recommended in certification document (SANDIA . It provides quantitative data (onset temperature, heat release, self-heating rate) used for thermal runaway characterization, thermal management and thermal modeling of battery.
Unlike regulatory abuse tests (UL 1642, UN 38.3, IEC 62133, Sandia/USABC SAND2017-6925, SAE J2464, GBT 36276-2023), there is generally no official “pass/fail” success criteria for ARC.
3. Can we measure amount of heat and gas generated during thermal runaway?
Yes, During runaway, ARC maintains nearly adiabatic conditions (no heat loss). This means almost all heat generated by the sample stays inside and is measured as a temperature rise. The ARC records the maximum adiabatic temperature rise (ΔTad). If the heat capacity of the sample + container is known, the heat released (Q) can be calculated:
Q (joules) = Mcell (g) x Cpcell (Joules/g.C) x Adiabatic T rise (°C)
4. How is ARC different from thermal ramp (oven) tests
Thermal Ramp test is a qualitative test (fire/no fire, explosion/no explosion, venting). Thermal Ramp is a regulatory safety abuse test. However, ARC provides Qualitative and Quantitative data (exothermic reaction onset, self-heating rate [dT/dt], pressure, pressure rise rate [dP/dt], heat release). ARC is more precise, provides detailed thermal runaway kinetic parameters, used in battery design, material evaluation, and thermal modeling.
In simple terms
Thermal ramp tells us – Will this battery blow up if overheated?
ARC tells us – At what temperature does runaway start, how fast does it heat itself, and how much energy and gas does it release?