Thermal Stability Test

Thermal Stability (Abuse) Test

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Description:

Thermal stability is a type of thermal abuse test where a cell is exposure to high temperature and to measure the maximum temperature at which a cell is stable indefinitely. That means cell does not go to thermal runaway. It helps battery pack engineers to implement safeguards in battery pack in such a way that battery temperature should never reach to this temperature

Test Procedure:

The test procedure involves starting with cell at 100% state of charge:

Heating the cell at 5˚C increment at a rate of 5˚C/min then holding at that temperature for 30 minutes.
If an exotherm of 1˚C/min is detected, then the temperature will be held at that temperature until the cell temperature stabilizes (+/- 5˚C oven temperature for 30 minutes).
Otherwise, this process will be repeated until

(1) an exotherm is detected

(2) Cell goes to thermal runaway, or

(3) Oven reaches maximum operating temperature of 250˚C.

Standards Followed:

SAE J2464 – Electric and Hybrid Electric Vehicle Rechargeable Energy Storage System (RESS) Safety and Abuse Testing

Equipment used:

Inhouse BSI setup to perform Thermal Stability Test

Picture 1: Inhouse BSI setup to perform Thermal Stability Test

Sample Test:

A typical 18650 cylindrical cell was subjected to thermal stability test. The test protocol for this test includes continuous monitoring of cell voltage and temperature throughout the test. Oven Temp & Cell Temp vs. time are shown for two different samples in the accompanying plot, with corresponding quantitative data summarized in the tables below.

Sample Plot:

Figure 1: Oven Temp & Cell Temp vs. Time plot for Sample 120

Figure 2: Oven Temp & Cell Temp vs. Time plot for Sample 130

Example Test:

Cell ID	Oven Set T	Cell Max. T	Peak Heating Rate	GO/NO-GO	Findings
Typical	°C	°C	°C/min	–	–
18650	148	594.6	263.3	GO	Thermal Runaway
18650	132	720.3	352.8	GO	Thermal Runaway
18650	119	123.2	4.11	NO-GO	No Vent Open
18650	123	128.3	4.35	NO-GO	No Vent Open
18650	122	129.2	4.35	NO-GO	No Vent Open

FAQ:

1. What is Battery Thermal Abuse Testing?

Battery thermal abuse testing is a safety test performed on batteries (especially lithium-ion batteries) to evaluate how they behave under extreme heat conditions that might occur during misuse, accidents, or external hazards. It is a type of abuse test where a battery is subjected to elevated temperatures beyond its normal operating range.

2. What is the purpose of thermal Abuse testing?

To check if the battery:

Undergoes thermal runaway (uncontrolled self-heating leading to fire/explosion).

Vents gases safely without ignition.

Maintains structural integrity or fails catastrophically.

3. Is Thermal Stability test same as thermal ramp test?

Although they sound similar, Thermal Stability and thermal ramp test are not the same. Thermal stability testing checks the highest temperature at which cell is stable indefinitely. While thermal ram test is often used to induce thermal runaway to study behavior and failure modes. It provides data on thermal runaway initiation temperature, maximum temperature reached, and energy released

4. Is Accelerating rate calorimetry (ARC) same as thermal stability test?

Although they sound similar, ARC and Thermal Stability test are not the same. Thermal stability testing checks the highest temperature at which cell is stable indefinitely.

ARC provides Qualitative & Quantitative data (exothermic reaction onset, self-heating rate [dT/dt], pressure, heat release). ARC is more precise, provides detailed thermal runaway kinetics Used in battery design, material evaluation, and thermal modeling. However, it is not possible to obtain visual observation of the test during ARC testing.