Fast charging in practice: why 10-80% says more than the peak-power figure

The peak charging power in kW is a marketing figure: it is often reached for only a few minutes, at a favourable state of charge and battery temperature. The usable measure is the time from 10 to 80% state of charge. This guide explains why. We make no recommendation.

The peak figure and the charge curve

A manufacturer states, for example, “up to 250 kW”. That is the top of the charge curve, not the average. The curve builds up from a low state of charge, holds the maximum briefly and then steps back down to protect the battery. Above ~80% the pace is sharply throttled. A car with a lower peak but a flatter, more broadly held curve can finish the 10-80% stretch faster than a car with a higher peak that drops off quickly (factory figure and owner/test figures; curves vary per model and software version).

Why 10-80% is the usable measure

On a long trip you rarely charge from 0 to 100%. Below ~10% you do not want to go, and above ~80% every percent costs disproportionately much time. The 10-80% stretch therefore approximates the real stopover. Factor in the added kilometres: a 10-80% session of ~25-30 minutes that yields ~250-350 km is a different practical story than the same time for ~150 km, even if both cars put “fast charging” on the spec sheet (indicative; figures vary per model and charge point power, owner forums and independent charging tests as the source).

Temperature and preconditioning

The charge curve applies with a battery at operating temperature. A cold battery in winter charges considerably slower until it has warmed up. Many EVs preheat the battery when a fast charger is set as the destination in the navigation (preconditioning); without that a winter session can take noticeably longer than the stated 10-80% time (self-reported on public forums, not measured by us). The temperature influence on range and charging is related; more on that in the tool below.

What you place side by side

Per model, compare not the peak figure but: the stated 10-80% time, the kilometres added in that stretch, and whether preconditioning works automatically. If a 10-80% time is not reliably established, we prefer to show that as n.b. rather than a derived estimate.

Indicative, no buying advice. Charging performance varies with charge point, software and temperature. Compare with independent charging tests.

Continue with the data: look at the electric models, calculate with the real-vs-WLTP tool and the range-by-temperature tool, or put candidates side by side in the comparator.