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A single AC USB charger for different devices

 
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Solis
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Joined: 05 May 2009
Posts: 1

PostPosted: Tue May 05, 2009 9:01 pm    Post subject: A single AC USB charger for different devices Reply with quote

Perhaps not the most technical question, but I've been trying to get a solid answer for something and I'm still left slightly confused.

I have 3 devices that charge from a USB AC adaptor: a cell phone and two digital video cameras. All use lithium ion batteries. The power output for all of their AC USB chargers according to the labels is +5V, but each has a different amperage rating (of .65, 1.0, and 2.0 respectively). All other specs seem to be the same, except that the cell phone charger shows a max AC input of 0.2a whereas the camera chargers are 0.3a (not sure if this matters).

Given that the only difference between these chargers is the amperage, would it be possible for each of them to use the same charger? From how I understand it, the 2.0a charger should work with all devices that require 2.0a or less? Or is having too high of an amp rating detremental and/or dangerous to devices which charge through USB?

The second question, which is perhaps slightly more fitting for this forum, is would it be possible for any of these devices to be charged directly from a PC USB port? With the cell phone, I noticed that you're supposed to be able to charge it when you have their software installed and running when you plug in the phone, but is there a way to use a PC's USB output as a universal charging device in the way that a wall socket charger is?
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Wed May 13, 2009 3:28 am    Post subject: Reply with quote

The USB standard voltage is 5 volts. You are right, as long as the voltage is what the device needs, the supply current just needs to be at least what the device needs.

For example a 12 volt battery that is made from 8 AA batteries or a 12 volt car battery will charge your mobile GPS unit just fine even though the car battery can potentially provide hundreds of amps of current.

The basic USB standard only provides for 500mA of current which is only 0.5 amps. There are some new standards which can provide more current in some situations but I wouldn't bet on it being present.

If those are the true charge requirements then I would not plug them into a computer USB port to charge. I am thinking that the numbers may be incorrect since I have never seen a phone yet that can't be charged using a computer USB port.
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