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A little modification...
on December 28, 2011
Smart phones and tablets have two charging modes: USB and AC. The mode the phone uses depends on what it thinks is charging it. If it thinks it is connected to a dumb charger it will go into AC mode and ask for as much current as it needs. If it thinks it is connected to a computer it goes into USB mode and asks for 500 mA because that is what the USB bus on most computers is capable of providing. Because of this, USB charge mode charges much more slowly than AC mode and on some devices that need a large amount of current (like iPads) USB mode might not charge your device at all (the device will still be receiving charge, just not enough, so it will lose battery, just at a slower pace).
When I hooked my phone into this charger it went into USB charge mode (500 mA) even though the charger is rated at 2.1 Amps (it is 2 Amps max shared between the two ports but I have not checked to see if that means 1 Amp per port, or if only one port is connected that single port can use the full 2 Amps). The way that your phone determines which mode to enter depends on if the data pins of the USB port are shorted together or not; if they are shorted (the data pins are the center pins of the 4 pin USB connector) it will enter AC mode, otherwise it thinks it is a computer port and will enter USB mode. On this charger the pins are not shorted. I have found this to be the case with the overwhelming majority of chargers I have experimented with. They are rated for 1 Amp or more but consistently put my phone into USB mode. I assume this is because you can buy regular USB connectors in bulk much more cheaply than you can buy a properly wired AC charging USB connector. So the ability to put out more than 500 mA is there, your phone just will never ask for more.
It is easy enough to fix the charger so that it will enter AC mode if you know how to solder. You just unscrew the power end of the charger where the fuse is, then use a flat head screw driver to pop the casing open down the seam. Once you do this you are left with the circuit board that the USB connectors are attached to. Solder the center pins together on each USB port (it's a somewhat tight fit soldering the port on the side where the LED is connected but completely doable) and then just pop it all back together. If you are careful in taking it apart you won't damage the casing at all. After doing this my phone and all other device I have tried report that they are in AC mode.
I have tried charging an iPad with this charger (both by itself and with another device connected) and in both cases it reports that it is "Not Charging". This leads me to believe that it is a max of 1 Amp on each port (the iPad needs 2.1 Amps, at least when the screen is on). If you put the iPad to sleep it charges fine, with or without another device connected on the other port. And again, when an iPad or iPhone says that it is not charging, it is still "charging" just not fast enough to meet the needs of the device so the battery will still get drained.
I hope this helps anyone who has had problems with the charger or is considering buying it. I think it works perfectly fine (then again I was irritated with it until I modded it). It is really difficult to tell if one of these chargers is wired for AC mode until you get your hands on it and try it out. And if you have a device that doesn't check the data pins and kick itself into USB mode you should get the full current of the charger without modding it. It is technically the phone that is limiting the current being delivered not the charger.
Wow, they raised the price on this charger to $20. It was $10 when I got it. I wouldn't pay $20 for it. Buy a mini or a micro charger that sits flush with your dash (or close to it). This charger is pretty big. Or get a charger that can do a dedicated 2 Amps on one of the ports. I'd say it is worth it for $10 but not much more.