PERFORMANCE
Now lets take a look at the performance. More to the point, what performance are we concerned with? After all, isn’t a charger a charger (I think we’ve already established that’s not the case)? First we tested the chargers ability to adapt its power output to the device being charged, then we tested the efficiency, and finally a couple of those safety features. One note to make here is that USB cables have their own set of specifications which allow some cables to carry more power than others. The differences in these cables is related to the intention of a cable to carry power and data versus a cable meant to carry only power. For testing I had only one cable available that was able to support higher power draw, and since I use this cable constantly, I just couldn’t destroy it for an inline current measurement.
For this test I used four devices of varying power draws:
- Amazon Kindle Fire
- Samsung Galaxy Note 2
- Samsung Avail
- LG Tone 700 bluetooth headphones
The fire was the only device that would draw over 1 A when connected to the correct cable, as indicated by the LED’s on the charger. To determine the efficiency we connected 4 devices and would measure the voltage and amps drawn to each device at various levels of charge then average them together. Since I have many USB charged devices, I have an actual use for my USB cables, so I was only willing to sacrifice one cable that would have to be continuously swapped around between the different devices in the test and the different ports on the charger. The power draw on a measureable cable for each device was as follows:
- Amazon Kindle Fire – .625 Amps
- Samsung Galaxy Note 2 – .362 Amps
- Samsung Avail – .676 Amps
- LG Tone 700 bluetooth headphones – .139 Amps
I was a bit surprised to see the Avail drew more power than the Note, but after trying multiple configurations the numbers were consistent. The total amps drawn were 1.802 amps at 5 volts each for a total power consumption of 9.01 watts. Compared to the input of .085 amps at 124.6 volts for a total of 10.591 watts, quick math will show that we get an efficiency of 85%. This is just 1% below the advertised efficiency which can easily be attributed to testing methods and my undoubtedly less accurate testing equipment. (I tested and measured each device multiple times at various states of charge to get an average of the amps and voltages, but I had to reconfigure between every test and Arctic would no doubt have better equipment in place).
If you charged 24 hours a day, 7 days a week, then you’re spending pennies to charge all your devices. With that in mind the efficiency of a USB charger may not seem important, but that’s exactly why we want to verify it, it might be a little more important if it was costing something more than pennies. In other words, 85% efficiency means you don’t notice anything on your electric bill, but if Arctic didn’t pay attention to this and put out a product on the extreme opposite end of the spectrum, say 5% efficiency, then that could potentially be enough to put a noticeable mark on an electric bill. So in this way, Arctic is watching out for our pockets as well.
When it comes to the protection of your devices, there was a bit of difficulty testing that. All of the devices I was charging for this test are personal, so I couldn’t damage them to get a higher draw and didn’t want to risk burning up my phone (for me, that would be a life-ending event). So I had to look for some other testing option. The only test I could think of was to put a constant current load on one of the ports and see how the device reacted. The results were interested. From a single USB port using a constant current DC load, I was actually able to draw up to 4.781 amps. What’s this telling us? The most likely answer is that the advertised 2900 mA per port and 4500 mA total limit is actually a result of the units logic more so that physical capability. While this does raise a question of the chargers capability to protect your devices, there was an accident during testing when all four ports were being used and live wires on the test cable made contact. This was an accident made during testing that I wouldn’t want to repeat due to equipment risk, but it is worth noting that the charger reacted exactly as advertised and stopped providing power to all devices immediately. Once the devices were all removed and reconnected, it was business as usual.
