Since a few years ago, I’ve been using an iPad charger to charge my iPhone. I always thought it charged faster, though I was never able to (or rather, never got around to trying to) verify it. Google gave mixed answers. Engineers and technical people said it doesn’t matter, that the iPhone will draw 1A regardless of how much current the charger is able to provide. Some people swear that their phones do charge faster.
First, some background. The USB port on a computer provides 500mA, or 0.5A. A standard iPhone charger provides 1A of current, while iPad chargers provide 2.1 or 2.4A. An iPhone plugged into a computer charges slower, and this is not surprising since the phone is only able to draw half the current it can normally draw. An iPad that is plugged into a computer will not charge, and may not even maintain the battery level if the iPad is being used. This same iPad plugged into an iPhone charger (1A) will charge, but slower than if it were plugged into an iPad charger (2.1/2.4A).
Then I started to wonder, if I plug an iPhone into an iPad charger, will the iPhone draw more current, and hence charge faster?
Recently, I suddenly thought of testing this out, and thanks to a cheap USB power meter, I was able to run a simple experiment.
It turns out, my perception of charging times was wrong! The iPhone draws 1A current from both chargers.
While randomly pugging the meter around, I seemed to notice that the USB cables seem to affect current draw as well. Perhaps if there’s interest, I can run another experiment on cables.