Two electric cars rated for the same peak charging power can differ substantially in how long a long journey takes. The reason is the shape of the curve rather than its highest point.
Peak power lasts a short time
A car reaches its advertised maximum charging rate only within a narrow band of battery state, usually low, and holds it briefly. Outside that band the vehicle requests considerably less.
The limit is set by the car, not the charger. A charging station simply supplies what the vehicle asks for, which is why a higher rated post does not always shorten a stop.
Advertised peaks are therefore a poor comparison tool. The useful figure is average power delivered across a realistic range of charge, which is what a driver actually experiences.
The curve tapers to protect the cells
As a lithium cell fills, the voltage difference driving charge into it narrows, and pushing high current becomes both less effective and harder on the chemistry.
The battery management system responds by reducing current progressively. The taper usually begins well before the pack is full and steepens as it approaches capacity.
This is why the last portion of a charge takes disproportionately long. The energy added per minute near the top can be a fraction of what it was at the start.
Short stops beat long ones
Because the curve is steepest at low charge, the fastest journey usually involves several short stops in the productive part of the range rather than a smaller number of long ones.
Charging to the top wastes time in the slowest section of the curve, and arriving at the next charger nearly empty spends time in the fastest section.
Route planners that account for this will often propose more stops than a driver expects, and the total journey time comes out shorter despite the extra stops.
Temperature moves the whole curve
A cold pack cannot accept high current safely, so the curve is suppressed until the battery warms. In winter the first minutes of a session may be spent heating rather than charging.
A hot pack, after sustained fast driving or repeated rapid charges, is throttled for the opposite reason, since additional heat cannot be removed quickly enough.
Preconditioning while driving to a charger addresses the cold case, which is why cars that know the destination is a charger will begin warming the pack in advance.
Pack architecture sets the ceiling
Higher voltage architectures can deliver a given power at lower current, which reduces resistive heating in the cables and in the pack itself.
Less waste heat means the cooling system can keep up for longer, so the vehicle sustains high power further into the session before tapering.
That structural advantage shows up in average charging speed rather than in the peak figure, which is precisely the number most buyers compare.