- Note: Please consult your product's user guide to determine compatibility with your device.
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.
Update:
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.
Buy AmazonBasics 2-Port USB Car Charger with 2.1 Amp Output (Black) Now
I have been using it since last two weeks now. This is simply awesome product.
I have used "Griffin Powerjolt Dual Universal USB Micro" before and AmazonBasic is much better than Griffin for following reason
1) Design: Griffin is so small that it gets stuck in the car charger. Amazon basic is perfect size .. neither too small nor too big (it looks huge in pics but actually is small)
2) Charging time: This is why you buy a car charger ... Amazonbasic is 2.1 amp vs griffin which is 1 amp... Amazonbasic charger charges phone twice as fast griffin. I use iphone 4 and it gets fully charged (from 10% battery) while i m listening to music in an hr
3) Quality: Griffin use to get very hot (and even my phone use to get hot) after 1 hr of charging ... amazon car charger is of much better quality ... I have used it all day and neither charger nor phones get hot
Overall I would highly recommend this product if u have a iphone (or any smart phone). Whether you are charging one device or two devices simultaneously it charges faster than any other product in market
UPDATE: Aug 28: Its been 10 months and this product is awesome... Actually I have noticed that my iPhone changes faster in car compared to even wall socket.
Read Best Reviews of AmazonBasics 2-Port USB Car Charger with 2.1 Amp Output (Black) Here
I've been using a now unavailable Kensington PowerBolt as my car charger, mainly for my iPhone 4, but occasionally to reanimate my iPad 2. A single USB socket is fine for commuting, but on long car trips when my car is filled with children and gadgets, a double socket makes for a lot less futzing.
I tested this by charging my iPhone 4 while in use, while simultaneously charging a Kindle Fire and it seems to work fine. On my 40 minute commute, I can add about 20% to the charge status of the Kindle while topping of the iPhone, all without any overheating or fuses popping. A couple years ago, I went through many chargers trying to find one that could reliably power an active iPhone, so I'm glad that cool running chargers have become so inexpensive even while powering two devices.
Devices I've tested and found to work:
iPhone 4
iPhone 4S
iPod Touch 3rd Generation
Kindle Fire
Kodak Playful pocket video camera
Sony Bloggie Touch camera (Needs a USB extension cable or it blocks the other charging port.)
Remington hair clipper
Jabra Extreme Bluetooth headset
Devices I've tested which didn't work:
HP Touchpad
Materials are pretty cheap looking, and the device is much, much larger than the PowerBolt; this makes it easier to insert and remove but I'd have been happier with something compact as the large size makes it easy to knock it out of kilter and stop charging which you might not notice while concentrating on driving. This can be really annoying. So not a perfect charger by any means, but a useful budget model.
Want AmazonBasics 2-Port USB Car Charger with 2.1 Amp Output (Black) Discount?
I am trying to get a 2.1 Amp (or atleast 1 Amp) car charger for my HTC Vivid and HP Touchpad (CM7). These devices consume lot of battery when using gps in car. I had lot of hope on the amazon basics car charger. However, both my devices get only 500 mA from these chargers (which is not sufficient for GPS usage). The devices recognize the chargers as USB port and hence only 500 mA. I have performed amperage analysis on both Vivid and Touchpad using currentwidget for android. See customer images.
01/02/2011 Update:
Well, few people have suggested me about "data pin shorting protocol" for phone to differentiate between real usb port and charger's usb port. I would like to question the rationale behind ME doing it instead of AMAZON (or whoever the manufacturer really is). My wall chargers already have these data pins shorted. They charge every device I throw at them including iPhone. So why can't amazon manufacture them with data pins shorted initially.
Also I would not recommend end user meddling with power electronics. I value my phone and tablet more than a $10 (now $20!!) car charger. No thanks. Its simply not worth the hassle when its time to claim warranty.
OK, here's the key thing. THERE IS NO UNIVERSAL STANDARD FOR HOW A HIGH-POWERED USB CHARGER SHOULD WORK.
One that does things the Apple way, like this one, will ONLY work WELL with Apple products (except, it seems, Amazon's Kindle uses the Apple way too).
One that does things the USB standard way -that has pins 2 and 3, (AKA D+ and D-) shorted when manufactured, will work WELL with most other products. (So will this one WITH the very laborious soldering modification others describe.)
Many reviewers don't realize that their power-hungry device is not charging as well as it can if matched with the proper charger.
For example: A charger with the data pins shorted won't be able to charge an iDevice except at the slow 500mA rate.
And its even more complicated the Apple way is actually not one way, but severalvarious voltages on D+ and Dmean various things, and prompt different power draws.
References: see the Wikipedia USB article (and its references). And I've been through many USB car chargers. Lots of 'em burn out if a device tries to draw more current than they can handle.
AMAZON GETS MINUS 2 STARS FOR HAVING A LOUSY DESCRIPTION OF THE DEVICE. THIS IS A TOTAL COP-OUT "Note: Please consult your product's user guide to determine compatibility with your device." WHEN THEY DON'T EVEN PROVIDE THE BASIC SPECIFICATIONS (I.E. EXPLAIN THAT THIS DOES *NOT* FOLLOW THE USB STANDARD.) I don't even know if it's UL or CE certified. With these devices, that's important, as certification requires better design/specs than many of the lower quality chargers out there.
