FTRC (Fractional Thermal Runaway Calorimeter)
Description:
Fractional Thermal Runaway Calorimetry is an experimental assessment that is performed to estimate the fraction of total energy released through a cell’s casing and through its ejecta material in the event of a thermal runaway. This data is needed by battery pack and container designer, and thermal modeler of battery pack.
The purpose of this test is to account for all the energy released by a cell in the event of thermal runaway in Belmont Scientific’s fractional thermal runaway calorimeter (FTRC). It seeks to do this by calculating energy gain and conductive losses over the whole system over time. The goal is to estimate the cell can energy, ejecta energy, and total energy of the cell.
FTRC test provides
- Can Energy
- Ejecta Energy
- Total Thermal Runaway Energy Gas Volume
- Separator Shut Down Temperature
- Vent Open Temperature
- Cell Peak Temperature
- Residual Weight
Equipment used:
- Inhouse BSI’s FTRC equipment
Picture 1: Belmont Scientific’s FTRC equipment
Picture 2: Schematic of a cell
Sample Test:
A typical 21700 Li-ion cell was heated to thermal runaway. Heat release (from cell casing) heated the holder and ejecta energy (from vent) heated the ejecta tube. Heat release from the cell casing (11 kJ) was estimated from the change in heat capacity of the holder and ejecta energy (108kJ) was estimated from the change in heat capacity of the ejecta tube. Total energy release from the cell was found to be 119kJ and it accounts for 9.1% of total energy from cell casing and 90.9% from ejecta.
Sample Plot:
Figure 1: FTRC result
Example Test:
Table 1: FTRC Test result
| Test # | Cell Type* | Initial Voltage, V | Weight Loss Percent, % | Maximum Cell T, ˚C | Total Energy, kJ | Cell Can Energy, kJ | Ejecta Energy, kJ | Cell Can Fraction | Cell Ejecta Fraction |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 21700 | 4.177 | 86.46 | 218.6 | 121 | 4 | 117 | 0.03 | 0.97 |
| 2 | 21700 | 4.225 | 86.42 | 218.6 | 122 | 6 | 116 | 0.05 | 0.95 |
| 3 | 21700 | 4.147 | 86.88 | 268.6 | 126 | 8 | 118 | 0.06 | 0.94 |
| 4 | 21700 | 4.137 | 86 | 343 | 115 | 11 | 104 | 0.13 | 0.87 |
| 5 | 21700 | 4.171 | 63.93 | 572.2 | 111 | 25 | 86 | 0.23 | 0.77 |
| AVG | 4.17 | 82 | 324 | 119 | 10.8 | 108.2 | 0.10 | 0.90 | |
| AVE DEV | 0.02368 | 7.2032 | 106.72 | 4.8 | 5.76 | 10.56 | 0.064 | 0.064 |
*Cylindrical cell 21700, 100%SOc
FAQ:
1. How is FTRC different from ARC?
The ARC is a good tool to measure total heat generated during thermal runaway but has a limitation of cell size and amount of heat generated but can not provide the information regarding what fraction of total energy is released from cell casing vs. ejecta as done by FTRC. In addition, FTRC can handle bigger cells and higher energy cells.
2. What kind of batteries could be tested by FTRC?
All cell formats of batteries pouch, prismatic and cylindrical cell. Cells with various chemistry like Lithium-ion, Sodium-ion, Lithium-metal, Solid state.
3. Who should do FTRC testing?
Battery pack and container designer, thermal modeler
Q (joules) = Mcell (g) x Cpcell (Joules/g.C) x Adiabatic T rise (°C)