Many users expect that a 90 W charger will charge a smartphone twice as fast as a 45 W one, but this is not the case. The reason lies in the principles of fast-charging technology, which does not allow maximum power to be used constantly. Here’s why doubling charging power does not lead to a twofold speed increase, and what actually affects real charging speed.

How Fast Charging Works

The main goal of fast charging is to provide high charging speed without overheating the battery, which could accelerate its degradation. To achieve this, manufacturers use complex algorithms that adjust power depending on the battery’s condition. For example:

  • A 120 W charger may deliver maximum power only during the first 1–2 minutes, after which it drops to 100 W, then to 80 W, to protect the battery.
  • An 80 W charger, on the other hand, may stay at peak power for longer, reducing the gap in speed compared to a more powerful adapter.

As a result, two smartphones with different chargers (for example, 80 W and 120 W) can reach 100% charge at almost the same time. That’s why manufacturers often specify charging time to 50% rather than to 100%. For example, “50% charge in 24 minutes” sounds more impressive than “full charge in over an hour.”

Why More Power Does Not Mean Double the Speed

Doubling charger power (from 45 W to 90 W) does not double the charging speed for several reasons:

  • Power reduction: Maximum output is used only at the start, when the battery is nearly empty. As it fills, power is reduced to prevent overheating, which narrows the gap between adapters.
  • Manufacturer algorithms: Different brands use their own fast-charging approaches. For example, the HONOR 400 with a 6000 mAh battery and 80 W charging takes 51 minutes to charge fully, while the realme 14 Pro+ with similar specs takes over 60 minutes. This is due to differences in optimization and temperature management.
  • Smartphone design: Charging efficiency also depends on the cooling system, battery type, and software settings—not just on adapter power.

In Short

Fast charging is a complex technology where doubling power does not mean doubling speed. Maximum power is used only at the start and then reduced to protect the battery. Differences in charging algorithms and smartphone design also affect total charging time. To understand real charging performance, rely on tests rather than just the charger’s stated power. This will help you choose a smartphone that charges quickly and safely.