Operating in extreme heat
What changes above 40 °C ambient, and how the car protects itself.
You'll learn
- Explain operating in extreme heat at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real vehicle
Overview
Above roughly 40 °C ambient, every radiator in the car loses much of its margin, and the thermal system shifts from radiator-led cooling to chiller-led cooling almost entirely.
In depth
| Ambient temperature | System behaviour |
|---|---|
| Up to 30 °C | Radiators handle most cooling duty; chiller rarely needed |
| 30–40 °C | Chiller assists increasingly, especially during fast charging |
| Above 40 °C | Chiller does most of the work; sustained high loads may trigger power derating |
Park in shade before a fast charge
A pack that starts a charging session cooler has more thermal headroom before the chiller becomes the limiting factor, often allowing a faster session.
Key takeaways
Remember this
- Radiator effectiveness collapses as ambient approaches coolant temperature.
- The chiller becomes the primary cooling path above roughly 35-40 °C.
- Pre-charge shade and timing can meaningfully improve fast-charge speed in heat.
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