how my phone can charge without being plugged into a power source


I have a USB charger plugged directly to the wall outlet without my phone plugged in. I remove the charger from the outlet and then connect the charging end to my phone. My iPhone makes the charging sound and shows that it’s charging for a second, then stops charging. Why does this happen?

PS. I noticed this in Europe since I’m currently traveling. I don’t believe I’ve seen this happen back home (US). Does it have to do with the higher voltage in Europe?

In: Technology

3 Answers

Anonymous 0 Comments

I can’t give a huge explanation because I myself don’t quite get it (I think).

But basically the brick that you plug into the wall and your cable into, is a transformer. It converts AC current of 120V and 15-20 Amps, to 5V and 2ish amps (depending on your brick quality) and DC current. And how it does this is with a couple of coils of copper wires and induction (??)

Inside the brick there are two coils and the basic gist is that it makes it safe for your phone and smaller everything (amps and volts). But these are some pretty hefty coils, and I’m pretty sure they, along with a few capacitors in there, can hold enough charge in them to give your phone the split second of charging. The one major varying factor that I’ve noticed, is that a brick with a rating of 5.2v and 2amps is much more likely to give it this extra little pulse than a brick with a measly 5v and 1amp….

So that’s how I understand it….I really hope someone covers all the other essentials I missed.

Anonymous 0 Comments

There is a capacitor inside the charger. It holds electricity, and take a few seconds to bleed down to zero. The phone sees the residual power in the charger, then it’s gone.

Anonymous 0 Comments

One of two things is happening:

1) The phone charger may have a capacitor inside it that’s storing a small amount of electrical charge, even after you’ve pulled it from the wall.

2) The motion of inserting the charger into your phone may be inducing a slight current, causing your phone to think it’s being charged. This is much more unlikely, since it requires there to be a magnet somewhere in the mix.