Power Banks and Fast Charging Explained: Watts, PD, GaN
By Sidra Salman · November 6, 2026 Last month I stood in an electronics aisle staring at a wall of chargers and power banks, and I realized something embarrassing: I write about gadgets for a living, and even I couldn't tell at a glance which of these bricks would actually charge my laptop. One box shouted "240W!" Another said "GaN II" like it was a movie sequel. A power bank promised 20,000mAh — a number it will never actually deliver to your phone. So I spent the last week reading the actual USB specifications, engineering guides from chip makers like Renesas, and a stack of independent buying guides. This is the plain-English version — the stuff that decides whether your phone charges in 30 minutes or three hours. Watts are the speed. mAh is the tank. Stop mixing them up. Capacity and speed are two different numbers, and the box puts the impressive-looking one in the biggest font. Capacity is measured in milliamp-hours (mAh). It tells you how much...