An operating temperature range defines conditions for the stated operation. It does not mean identical capacity or power at every point in that range.
Charge
Charge method and temperature window
Discharge
Load, cutoff voltage and heat transfer
Storage
Temperature, SOC and duration
Charging, discharge and storage are separate
Keep the charging window, discharge window and storage requirements separate. A low-temperature discharge statement does not establish permission to charge at that temperature. Test curves from another model are useful reading examples, not specifications for this catalogue.
Reference: Molicel · Example of condition-dependent cell curves
Load affects voltage and heat
Ambient temperature differs from the temperature inside or on the surface of a working cell. Load, layout and heat removal affect that difference. As a simplified electrical reference, resistive voltage drop scales with I × R and resistive heating with I² × R. These relationships do not supply a complete cell thermal model.
Resistive reference: ΔV ≈ I × R Resistive heating reference: P_heat ≈ I² × R
Read the curve conditions
For an energy or power requirement, ask for the relevant discharge curves and their initial SOC, current, voltage cutoff and temperature. AC impedance and DC pulse resistance use different measurement methods; retain frequency or pulse duration, SOC and temperature when comparing them.
Reference: INL / US DOE · Battery Test Manual for Electric Vehicles
Questions to prepare
- What are the ambient conditions during charging, operation and storage?
- What airflow, enclosure or cooling arrangement is planned?
- What energy and peak-load requirements apply at the temperature extremes?
Common questions
Can a storage limit be used as an operating limit?
Use the condition for the corresponding operation, including storage duration when specified.
Is a warmer ambient the same as a hotter cell?
Cell temperature depends on the load and heat transfer as well as the surroundings.