I always seen these USB charge boosters on sale all over the place.
But I never trusted them, since there was no way I could actually see wheter it was working or not other than through a gut feeling. But a few weeks ago I acquired a USB voltage meter, so now I CAN see wheter it works or not!
A disclaimer before hand, I'm not an electrician, but just someone who has read up on the topic on the Internet so if anything blows up when you try this. Don't blame me.
The speed of your charging depends on how many AMPs flows into your device, based on this Wikipedia article on USB charging we find out that normal USB ports usually only supply 500mA whereas it's possible for a dedicated charging port to deliver more than that.
I've measured most of my USB power sources previously, and other than the dedicated power plugs which came with the phones, they all delivered only 500mA of current when charging. Whereas the dedicated plugs could supply roughly 1A.
So I tested it with the the charger in my car, a Kensington Duo Powerbolt Charger first we use it without the charge booster.
And the charger supplies juice at a current of 0.5A. Next we plug in the charge booster.
Now the current is around 0.8A, definitely higher although not exactly the 2 times faster that the box is talking about.
So I guess it DOES work, even though it might not be as good as they say it is but I guess every little bit counts when it comes to juicing up your devices faster.
One interesting caveat though, the booster has 2 modes of functioning, one is where it'll boost your charging but it means you can't transfer data with your PC in this mode even if it's connected to a PC's USB port. The other mode is normal mode where you can sync data with your PC. My Nokia Lumia 1020 behaved EXTREMELY weird when connected to anything in this mode, basically the phone kept dropping in and out of charge mode, probably due to how the current is being passed through it. I recommend that if you do get this and you need to be NOT in boost mode? Just don't plug the thing in.
Because of this little issue, I have a theory about how this thing works. According to the Wikipedia article a dedicated charging port is identified by shorting it's data pins, so what this charge booster is doing could just be that it's shorting the data pins when it's on so that the device knows it can draw more current from it.
You can find this thing around town, I've seen them selling between RM60 to RM40 under various brands (since it is some China OEM product I guess) The cheapest price was at IP Mart so you can go check it out if you're interested.
A few more things to be aware of before you go.
- Charging at a higher current heats up the battery/device faster. And since doing data transfer intensive processing on the device (like using Waze) also generates a ton of heat on the device, your device might get pretty hot with this. And then 2 things might happen, either the battery stops charging due to it's thermal protection circuit, or if the thermal protection circuit is faulty the battery *might* catch fire. :P Depends on the ignition temperature of the components inside the device I guess.
- Someone once told me that if you had a device that was drawing much more current than the power supply could provide at best nothing happens and your device doesn't get charged, at worst you damage the power supply.
Scared yet? ;)