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Why some phone chargers are faster than others (video)

By Joe Levi July 25, 2014, 2:04 pm
Pocketnow Power User

Whether you’re using Android, iOS, or Windows phone, there’s one thing that unites us all: phone chargers.

This week, Natalie and Kristin want to know why some chargers charge phones faster than others. Kristin bought a brand new phone charger that charges her phone about twice as fast as Natalie’s in-wall charger. What gives? To answer that, first we have to talk a little bit about electricity.

We’ll dig into that, get into some Ohm’s Law, and talk about rectifiers and inverters on this episode of the Pocketnow Power User.


The power inside our walls is AC (alternating current). The power that our phones and other mobile electronics use is DC (direct current). Somehow we’ve got to convert that AC into DC so we can charge our phones and tablets.


This conversion from AC to DC electricity happens inside our chargers (which are actually rectifiers, although some incorrectly refer to them as inverters). What they do is take the AC and, through a series of circuits, convert it into DC for use in our phones.

In electronics we live by something called Ohm’s law that explains the interrelation of Amps, Volts, and Ohms. All of our phones these days use USB (or Apple’s equivalent) to charge. Since USB charging is all done using 5 volts DC, how come some chargers are faster than others?

The other two variables are resistance (measured in Ohms) and current (measured in Amps). Resistance shouldn’t be a big deal unless you’ve got a cheap cable or charger, one of them is damaged, or one of the connectors is loose (in which case, resistance will be higher). What’s more likely is that your charger outputs fewer Amps.

The lower the Amps, the slower the charge.

Generally speaking, the more Amps that you push into the device, the faster it will charge. Keep in mind, however, that your device is only designed to charge at a certain rate. Trying to push more amps than your device is designed for will probably result in irreparable damage.


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