Some micro USB cables charge faster than others, why?

[Ricerocket]

I made myself a custom car dock for my GS3 so I could use my Titan Kraken case modified to take an extended battery. The setup works great, but I've noticed something very strange. I have an NFC tag in the dock to launch Carhome Ultra. I was noticing that on my 30 drive home from work, my battery (which is charging in the new dock) would discharge about 2%. I was using a generic micro USB cable plugged into my Ravpower DC adapter, which maxes out at 2.1 amps, which is plenty. As an experiment, yesterday on the way home, the first 15 minutes I had the generic cable plugged in. After it dropped a percentage point, I unplugged the generic cable and plugged in a cable I got with a Mophie that I had. The last 15 minutes of the trip it went up 2 percentage points. Keep in mind, same DC adapter, same phone & battery and same apps running.

Can anyone explain why this is? I have experienced the same drop with at least 2 other cables. The Mophie cable and one other that I have will 'keep up' with the power demands and actually charge the battery too.

Just wondering what I should look for when buying USB cables in the future.

 

[FoxKat]

Interesting hypothesis but it goes against all that I know about cables. There are simply wires running from one end of the cable at the connector to the other end at the connector. The size of the wire should easily be sufficient to carry substantially more current than the phone is pulling without having a negative effect on the output. We're not talking rocket science here, simply electrons traveling along a stranded copper wire. Only over LONG runs is there enough resistance in these cables to attenuate the current and/or voltage at the other end. Over the short distances of these cables it may be barely measurable differences on a high resolution scope.

I suggest the differences could have been related to something other than the cable, such as perhaps whether the phone was in an area with strong signal strength versus weak (which will cause the phone to consume more power). It's not uncommon for a phone to use more power while in operation than the charger can supply, and result in the battery actually losing power rather than being charged. This is (dare I say), virtually ALWAYS related to what the phone was doing and/or signal levels that cause the phone to consume more at one time than at another. For instance, if using navigation and also streaming internet radio via Bluetooth to the car's head unit, the phone may very well consume at a rate faster than the car adapter supplies.

 

[wcjeep]

I've seen this problem before. It was always with the Vzw Nexus I had. Cheap cables were bad for charging while running navigation and Pandora. Expensive cables would usually do better but not great at charging the GNX. It used to be possible to buy higher gauge USB cables. Not sure now. My S3 is alot more efficient at power consumption.

 

[Ricerocket]

I understand and agree with all of your points foxkat. The only problem is that this is an observation that I have made over the course of several days. Coming home from work today, taking the same route and same apps running (most notably carhome ultra) using the Mophie cable the battery went from 80% to 84%. As I mentioned earlier with the other cable my percentage would do usually 2 percentage points. I have even noted this behavior running carhome ultra with my phone docked at home plugged into AC (more as a test than anything).

I have also noted this behavior on another Galaxy S3 that I have that I'm selling...

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