Designing Multi Temperature Thermal Soak Schedules for Commercial Battery Dossiers
Multi temperature thermal soak schedules isolate micro shorts and establish valid cell voltage decay dossiers prior to volume cell procurement.
Thermal Chamber Uniformity
Meaning
Spatial temperature consistency across a test volume ensures that all specimens experience the same environmental conditions during validation. Achieving thermal chamber uniformity prevents localized hot or cold spots from skewing the results of a large batch of cells. Fans and baffles direct airflow to eliminate gradients that might cause one side of the chamber to be warmer than the other.
Mapping the heat distribution is a standard part of equipment qualification.
Spatial Variance
Deviations in temperature across different rack positions can lead to inconsistent aging or capacity results. When thermal chamber uniformity is poor, a cell in the corner might be two degrees warmer than a cell in the center. This small difference significantly alters the internal resistance and discharge curves of the units.
Laboratory standards usually require the variance to stay within one degree Celsius.
Sensor Grid
Calibration procedures use a distribution of thermocouples to verify the air temperature at multiple points. Mapping the thermal chamber uniformity involves placing sensors at the top, bottom and corners of the internal volume. The data from these sensors is recorded over several hours to ensure the stability of the air currents.
This grid provides a three dimensional view of how the heating and cooling elements interact with the load. Technicians use this map to identify dead zones where airflow is blocked by the test fixtures.
Environment Consistency
Maintaining a stable climate is the only way to ensure that tests performed in different locations are comparable. If the thermal chamber uniformity is verified, the lab can guarantee that every cell in a module test experienced the same stress. This level of control is necessary for meeting international testing standards like ISO or UL requirements.
Reliable spatial data allows the lab to certify the results for commercial use.