WOBBLpack.py
Will this battery pack overheat in a sealed box during a one hour discharge?
HOT
Hottest point reaches 74.5 C (limit 60 C) at (18.5, 18.5, 31.8) mm after 60 min. It passes 60 C after about 21.1 min.
max temperature
74.5 C
limit
60 C
power
6 W
mesh nodes
9,610
Confidence high
- passed mesh convergence, energy balance, hand calculation, units and sanity
Checks
| status | check | result |
|---|---|---|
| pass | mesh convergence | temperature rise at the hottest point settled: 39.5 -> 39.5 C over 2 meshes, last change 0.0% |
| pass | energy balance | over 60 min, heat in 21.6 kJ, stored 7.98 kJ, out through the surfaces 13.4 kJ (1% apart) |
| pass | hand calculation | lumped model with convection and radiation (Biot 0.012) gives a mean of 72.2 C at the end; FEA mean is 72.8 C (1.6% of the rise) |
| pass | units and sanity | temperatures between 69.5 and 74.5 C |
How to fix it
Raise heat transfer about 2x
The temperature rise scales with 1/(h A). A small fan takes h from about 5 to 25 W/(m2 K); fins or a larger case add area. Either way you need about 2x the current 5 W/(m2 K) times area.
Cut the power to 3.04 W
Lower current or duty cycle; the rise is proportional to the heat made.
Assumptions
- Li-ion cell (lumped, effective): conductivity 3 W/(m K), specific heat 950 J/(kg K), density 2500 kg/m3.
- Heat is generated evenly through the part.
- Convection uses a fixed film coefficient; real coefficients vary with temperature and airflow.
- Surrounding air or coolant at 35 C does not heat up.
- Radiation with emissivity 0.9.
- Contact resistance between parts and internal airflow are not modeled.