Product Description
USAMS (Black) Compact High Output Dual USB Car Charger - 3.1A Output Ideal for Charging iPhone, iPad, iPad 2, new iPad and iPad Mini as well as Galaxy, Blackberry, HTC, Droid, GPS, and Other Tablets, Smart Phones and USB Powered Devices (Data cable not included).
Product Details
- Amazon Sales Rank: #85 in Single Detail Page Misc
- Size: Mini
- Color: Black
- Brand: USAMS
- Model: USAMS31-B
- Dimensions: 1.00" h x 1.00" w x 1.75" l, .3 pounds
Features
- USAMS Dual Port USB Car Charger charges your iPad, iPhone, iPod, HTC, Blackberry, MP3 Players, Digital Cameras, PDAs, Mobile Phones
- Input:12-24V 2000mA; Output:DC 5V 3.1A or 5V 1A (A max. total of 3.1A)
- Dual Port Design, one 2 Ampere port for iPAD and one 1 Ampere port for Mobile phones or other devices.
- Use your existing USB charging cables to charge most USB powered devices
- Small light weight mini profile design for snug fit to any standard cigarette lighter adaptor
Most helpful customer reviews
26 of 26 people found the following review helpful.
Buyer beware - yet another fraudulent product!
By Paul Clifford
I bought this auto-to-usb adapter in part because as an electrical engineer I was intrigued at how the manufacturer packed a 3A adapter/charger into such a small volume. As it turns out, they hadn't -- this is not a 3A charger. Although they disingenuously marked the specifications right on the enclosure as "5V 3.1A" this power adapter in fact can supply only a little more than 1A.
I first tested it by placing fixed resistors across its output, noticing that whenever I tried to supply more than 1.5A the output would start cycling ON and OFF. So, I opened it up to see what's inside.
What I found is that the unit uses an FR9886 switching regulator IC (you can easily find its datasheet on the web). The FR9886 is rated for a maximum 2A output, but only if the IC is mounted and heat sunk properly. If the chip overheats, it shuts itself OFF automatically, and turns itself back ON a few seconds later. If the chip is mounted and heat sunk correctly it can provide 2A. And if you connect an appliance that draws more than 2A it will overheat and keep cycling on/off.
Unfortunately, in this product the chip is not heat sunk very well, so you can't get the full 2A out of it. I tested it further and found that it can sustain a 1A load continuously at an ambient temperature of about 20C. If the enclosure is opened so that it's circuit board is exposed to free air, at 1.5A and an ambient temperature of 20C it works (although the chip gets very hot), but at an ambient temperature greater than 30C the chip overheats, and it starts thermally cycling. At a load of 1.75A or more it always overheats within a minute or less. As it enters thermal runaway its output increases to 5.6V (which may harm the device you are charging) at which voltage it cuts-out, only to turn back on a few seconds later, repeating the cycle, ad infinitum et ad nauseum.
Even so, I found in testing that the unit can sustain a 1A load continuously. At that current the regulator chip inside gets hot, but not too hot to continue functioning. Because of its built-in thermal protection, this product is a rather nice 1A adapter, so long as the device being charged can withstand the maximum of 5.6V provided just before thermal shutoff.
As an aside, the product overview describes the two ports as "one 2 Ampere port for iPAD and one 1 Ampere port for Mobile phones". In fact, the two ports are connected directly together and behave interchangeably. Their data lines are both connected together, and they both provide a "fast charge capability" signal to the device being charged. Some reviewers noticed different behavior from the ports, but I think that their adapter had already overheated, and they were simply noticing the confusing time-dependent auto-shutoff/recovery behavior of the adapter.
You can safely draw 1A from this adapter, but no more. However, it is marketed and sold as a 3.1 A device, and that is simply commercial fraud. I do not know, but assume, that the certification agency marks on the enclosure are all forged. This product could never have made it through the most rudimentary testing. It may be that at one time there had been a similar looking product that was genuine, but that has now been replaced with a counterfeit. With counterfeits so prevalent it's difficult to know if the various reviewers here have even reviewed the same product or not.
If you charge a device that draws less than 1A this adapter may work for you. But if it requires more current you'll see all sorts of unpredictable behavior. Further, the adapter fraudulently reports itself (by signaling on the USB data lines) as a fast charger adapter to the phone or tablet. Some phones/tablets may react badly to an adapter that misrepresents itself; they try to draw the specified current then cycle their charging circuitry when the required current isn't forthcoming, resulting in a drained battery instead of a charged one. Other phones/tablets may degrade more gracefully. Still others may be harmed when the adapter goes out of regulation and provides too great a voltage just before it thermally cycles off. You may see all kinds of unpredictable behavior.
I understand how difficult it is to test products like this, but I wonder how much of Amazon's revenue accrues from selling fraudulent products like this one?
8 of 9 people found the following review helpful.
Terrible...DO NOT BUY!!
By Dlearious
Waited 3 weeks to receive item. The first time I used the item it fried. Literally, the unit smoked and was clearly defective. This item was junk, never worked
4 of 4 people found the following review helpful.
Stopped working after 2 months.
By John N.
I barely used it, and it stopped working after 2 months. It didn't play well with my HTC One S either. Sometimes it would charge fine, other times the phone would say the charger was not compatible.
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