Charge Curve
A charge curve is a graph that plots an EV's DC charging power (in kW) against the battery's state of charge (SoC percentage). It reveals how charging speed changes as the battery fills up — information that peak charging speed alone cannot convey.
How It Works
When you connect an EV to a DC fast charger, the Battery Management System (BMS) negotiates with the charger to determine the maximum safe charging power at each moment. This power level depends primarily on the battery's current SoC, temperature, and cell chemistry.
Most EVs accept their highest charging power at low SoC (typically 10–30%), then gradually reduce power as the battery approaches 80%. From 80–100%, charging slows dramatically to protect cell health. This tapering pattern creates the characteristic shape of the charge curve.
A "flat" charge curve that maintains high power across a wide SoC range (like many 800V vehicles) produces the fastest real-world charging experience. A curve that drops steeply after 30% SoC will feel slow even if the peak number is impressive.
Why It Matters
The charge curve is arguably more important than the headline peak charging speed. An EV with a 350 kW peak that drops to 100 kW by 30% SoC may charge slower overall than one with a 200 kW peak that holds steady until 60% SoC.
On EVKX, every EV has a detailed charge curve chart showing power at each SoC level, plus calculated 10–80% charge times — the most practical metric for comparing real-world charging speed.
Key Metrics
- Peak power: the maximum kW the car can accept (often at 5–15% SoC)
- Average 10–80% power: better indicator of real-world speed
- 10–80% time: the benchmark charging duration, typically 18–45 minutes
- Optimal arrival SoC: 10–15% for fastest charging stops on road trips