29 August 2026
Fast charging explained: what the watt number really means
A 65W charger will not make a 20W phone charge three times faster. Here is how the negotiation actually works, and how to pick the adapter your device can use.
Every fast-charging claim comes down to one thing: how much power the phone is willing to accept. The charger only offers; the phone decides.
Volts, amps and the handshake
When you plug in a USB-C charger, the two devices negotiate a profile — 5V/3A, 9V/2.22A, and so on. The wattage printed on the adapter is the ceiling of what it can offer, not what your phone will draw.
So is a 65W charger wasted on a phone?
Not wasted, but not magic either. A 65W GaN adapter will charge a 20W phone at exactly 20W. What you gain is headroom: the same charger also runs a laptop, and it runs cooler because it is never at full load.
The cable matters more than people think
A cable rated for 3A cannot carry a 5A profile no matter what is on either end. If your 100W laptop charges slowly, check the cable before blaming the adapter.
Practical advice
- Match the adapter to your fastest device, not your slowest.
- Buy one good cable rather than three cheap ones.
- Heat is the enemy of battery life — charge on a hard surface, not under a pillow.
