Isothermal Battery Calorimeter (IBC)
An Isothermal Battery Calorimeter (IBC) is a specialized calorimeter designed to measure the heat generated by batteries under controlled and constant temperature (isothermal) conditions. IBC is primarily used
- To quantify heat generation during charging/discharging cycles.
- To evaluate efficiency and thermal performance of batteries.
- To provide data for thermal management system (TMS) design and safety assessment.
The battery is placed inside a thermally insulated chamber maintained at a constant temperature (isothermal environment). Any heat generated by the battery is absorbed by a heat transfer fluid (often water or oil) circulating around the test chamber. The calorimeter measures the heat flow using sensitive heat flux sensors or by monitoring the temperature rise of the fluid.
ITBC test provides
- Heat generation rate (W) during cycling.
- Reversible heat (from entropy changes in electrode reactions).
- Irreversible heat (from resistive/ohmic losses).
In battery research and safety testing, the applications of IBC are:
- Characterizing heat generation of new battery chemistries (Li-ion, Na-ion, solid-state).
- Comparing performance at different C-rates, temperatures, and duty cycles.
- Providing data for pack-level thermal design.
- Researching how operational conditions affect battery lifetime.
Standards / References:
ASTM D7896 – Standard Test Method for Heat Generation Rate of Batteries by Isothermal Calorimetry
This is very close to IBC – it specifies how to measure heat flow under isothermal conditions.
Equipment used:
- NETZSCH IBC 284
- Battery Cycler
NETZSCH IBC 284
NETZSCH IBC 284 Schematic
Test details:
The calorimeter has been designed to drive the heat generated by the battery through the heat flux sensors located underneath the bottom plate of the calorimeter, on which the battery sits. To achieve high precision and high temperature stability, the calorimeter is submerged in more than 30 gallons of temperature-controlled heat transfer fluid. Heat generated and/or absorbed by the sample is measured using sixty high-sensitivity heat flux sensors specifically selected for this kind of application. The temperature of the lower side of the heat flux sensors is controlled by the isothermal bath. The temperature of the upper side of the heat flux sensors is influenced by the battery. When a thermal event occurs in the battery, changing its temperature, the temperature of the upper side of the heat flux sensors changes, generating a voltage proportional to the temperature difference between the two sides of the heat flux sensors (Seebeck effect). This voltage is converted into a heat flux signal, in milliwatts, using a calibration coefficient. The calibration is performed using a high precision resistor through which a controlled and monitored current is applied.
Example Test:
A prismatic cell was cycled (charge and discharge) at P/4 for three times in an isothermal temperature of 25˚C. Data collected were cell voltage, current, power and temperature and summarized in figure 3 below. In addition, heat flux was measured and total heat energy generated during cycling was calculated and summarized in Figure 4 below. It was found that heat generation was significantly higher during discharge than the charge. An average of 16.12 +/-404 kJ of energy was generated during charging at P/4 was significantly lower than the energy released 64.67 +/-144 kJ during charging.
Figure 3: Battery thermocouple temperatures during P/4 charge/discharge cycles. Maximum and minimum temperatures are marked.
Figure 4: Analysis of the heat flux peaks, calculation of total heat energy, and battery efficiency during P/4 cycles.
FAQ:
1. Who requires Isothermal Battery Calorimeter (IBC)?
- Battery thermal management designer.
- Battery management systems, BMS designer
- Automotive and energy storage companies designing safe battery packs.
2. How is IBC different from Accelerating Rate Calorimeter (ARC)?
- ARC (Accelerating Rate Calorimeter) → For abuse and runaway testing (adiabatic conditions).
- IBC → Quantify heat generation during normal operation (charge/discharge) (isothermal conditions).
In short, the IBC is the tool of choice when you want to measure how much heat a battery produces during normal operation rather than during abuse or runaway conditions.
3. Why is IBC important?
- Provides accurate heat generation data.
- Supports thermal management system (TMS) design.
- Helps improve battery safety, performance, and efficiency.
- Supplies input data for battery thermal models.
4. What is the temperature at which the test can be done?
The temperature window is –20 °C to +60 °C in the isothermal bath.
5. What kind of batteries can be tested?
Prismatic and pouch cells of minimum size 4” x 4” and maximum size of 9” x 12”.