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> chargers and cables are advertised with the wattage they support, but it's really the voltage and current that matters.

watts = volts * current

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GP's point is that although chargers are labeled with wattage, they can't output any combination of volts and currents as long as they multiply to the stated wattage. Can you take a normal 100W charger and ask it to output 100V and 1A? It can't.

The Apple 29W charger supports two configurations only: 14.5V × 2A, or 5.2V × 2.4A

The Apple 30W charger supports these four instead: 20V × 1.5A, 15V × 2A, 9V × 3A, 5V × 3A

Do you see a problem here?

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