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Mediabridge makes two versions of this dual USB charger. This one is for devices that use the USB standard for charging devices: Samsung, Kindle, Motorola, LG, and so forth. The plastic case is grey, and the box is labeled "12 Volt USB Charger 3.1 Amp Shorted Grey". Note the words "shorted" and "grey".
The other version Mediabridge High Output Dual USB Car Charger For iPad and iPhone (Dual Port High Output Design: 1.0 Amp USB for iPhone; 2.1 Amp for iPad or additional iPhone) is for Apple products, and has a black plastic case.
Since 2007, the USB standard says an A/C adapter that can supply more than 500mA (1/2 Amp) should identify itself by connecting together ("shorting") the two data lines (the middle two of the connector's four wires). This charger does that. Apple expects a charger that can supply more than 500mA to identify itself by putting 2.0 volts on one data pin and 2.8 volts on the other (with respect to the ground pin). Obviously, if the two data pins are connected together (as required by the USB standard) they will have the same voltage; one can't be at 2.0 volts and the other 2.8 volts.
What this means is you can't make a charger that just works with products that comply with the USB standard and also with certain Apple products. Most of the dual chargers have one USB socket that works with Apple and one socket that works with standard products. That's great if you have both products. If you don't have any Apple products, then you're paying for a dual charger and only getting a single working socket with those products. With this one, both sockets work!
Some chargers are designed to work with Apple products but come with a special cable that shorts the data pins. With those chargers, regular USB cables will charge Apple products but the supplied cable won't (at least, not at high current). And regular USB cables won't charge standard products at high speed, only the supplied cable will. I think this is just asking for trouble. Not only do you have to keep track of which cable to use for charging, it also introduces a cable that looks like a USB cable but won't work WITH ANY PRODUCT for connecting to a computer for data (because the data lines aren't connected properly). Why would anyone want to have a cable like that floating around, just waiting to cause trouble?
So, bottom line: if you don't have Apple products to charge in your car, this is a great dual charger. If you only have Apple products, order the black version instead. And if you have a mix of standard and Apple products, look for the dual chargers that have one socket for each (but watch out... most of those have low current on the standard socket and high current only on the Apple socket).
One small problem: this product came with the manual for the Apple product (the black plastic model), which says it is compatible with iPad and isn't compatible with Samsung Galaxy or Motorola Xoom. That's wrong. Just ignore the manual.
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When driving with the GPS and Bluetooth on, the power on my Samsung G3 would drop faster than the regular charger could replace it, especially if you make a few calls. On road trips, when my wife is driving and I'm playing games, it was even worse. With this charger I can put on 1% in about 8 min if I'm off the phone with GPS and Bluetooth is on if it's plugged into the 2.1 amp slot. We have two 12v sockets in our cars so I cannot speak to charging a low use device in the 1.0 amp slot at the same time.
I am also able to charge/use my 8.9" KindleHD 4G LTE in a similar fashion.
This review is focus on the light grey android version, not the black Apple version. While I have heard conflicting reports about whether they are interchangeable, my friend has a black apple version and it seemed to charge my Samsung phone and KF HD w/o a problem so it you are a member of a mixed race family (Android/Apple) you can probably share...just don't hold my feet to the fire on this, it worked w/o problems for my equipment (Apple working on Android devices) on 2 long trips. It was what convinced me to buy the android version. I would email rhe company if you have any questions.
You WILL get an email directly from MediaBridge after your purchase asking if you have problems and they will respond...how often does that happen these days.
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The documentation in the package is wrong. It states that the charger is only useful for Apple products and not for Samsung, Asus, etc. This is incorrect. It is perfectly suitable for charging non-Apple devices, IOW, as advertised.
I checked the wiring and found the D+ and D(green and white wires) are appropriately shorted together. This is in compliance with the USB standard for high-current charger devices. (Apple uses a completely different wiring and voltage signaling scheme on D+ and D-, which preceded the USB standard now used by everyone else).
I then tested the actual output using a variable current load. The "1.0 AMP" socket produced about 1.4 amps before the voltage dropping to about 4.2V. The "2.1 AMP" socket went to about 1.9 amps before dropping to about 4.3V. Part of the voltage drop was due to the cables I was using, so the actual voltage at the socket was a bit higher. This is fine.
So, ignore the supplied documentation. The voltage and current capability is perfectly well suited for charging the big batteries in your USB devices. It essentially supplies the maximum current permitted by the Standard. The so called 2.1A rating is a nominal upper limit, and generally no device, for example my Nexus 10, pulls more than about 1.8 amps.
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Well made and shipped quickly. Plugged it into cigarette lighter outlet using regular power/data usb cable and Nexus 7 Android system settings/battery shows charging as AC.
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Now that we are a smartphone-using, ipod-playing, tablet-reading household, we often need to charge multiple items simultaneously in the car. We leave this plugged in with two cables (one for phone, one for 30-pin iPods) and never have to worry about whether we have the right stuff to make sure we can stay connected while we're mobile.
