Is your Android device charging slowly and you can't explain it? This is why.
USB cables have a data wire and a charging wire within the cable itself. Most USB cables, probably over 99+% are 28/28. Buying after market micro USB cables will pretty much always result in getting cheap quality 28/28 cables and your device will barely break 500mah when it charges, maybe even less.
This isn't the only issue though. After you use a cable for a while it pushes slight stresses on the micro USB connector itself and compresses it. This causes poor connectivity between your device and the wire. This is why it seems like your device port feels like it's getting loose and you think something is wrong. It's most likely the cable being slowly damaged over time.
Solution? Get a 28/24 gauge cable. 24 gauge is ~ 60% larger and can handle 2amps. This is what is usually sent when you buy a tablet or large phone device. Your wire slowly gets damaged over time or may even stop working entirely. You order a cheap cable off Amazon or eBay and it never appears to charge at the correct speed anymore.
For the longest time I always thought my actual chargers were slowly dying and my charging speeds were getting worse but it turned out to almost always be poor quality cables.
Monoprice is the only place I have found that lists their cable gauges. Here is a search for the correct term. 28/28 cables still show up so make sure to order the right cables if you need them.
Buying better quality cables is always better, but here is some more info. As far as the quality of the conductor itself, copper is always the best option. USB cables should be copper. Copper wire doesn't get "slowly damaged over time" just from conducting electricity. Other types of cheaper conductors do, sometimes made of aluminum and other materials. And even those materials fail because of physical stress and fatigue or corrosion. Not because it has conducted x amount of current for x amount of time and had reached its end of life.
Over time the connector does fatigue as you said but it's important to note that the port on your phone also does this. But at different rates depending on the quality of both the port and the connector. Higher quality cables are more likely to have tighter tolerances in manufacturing the connector on the cable and use better materials too, but if you have a poor quality phone/charging port or you dropped it on the charging port while it was plugged in, a good quality cable won't help you.
While 24 gauge wire can "handle" higher current than 26 gauge, ultimately it's up to the charger (wall plug/wall wart) to provide this. Getting a bigger wire won't increase your current unless the charger is capable of providing that. Chargers don't have the capability to "measure" the gauge of wire connected to it. On a larger scale this could be dangerous if the charger provided current greater than the current capacity of the wire. In extreme worst case design scenarios, it would then ignite and act as a fuse and the wire would break. Instead, you device controls how much current is drawn. A bad cable can make the best chargers charge weakly. The phone can't tell the difference between a thin cable and a weak charger. And as far as charging speed, the difference doesn't matter.
For getting a fast charge it's important to get a charger that has at least the same output as your original one. Look for something that says "output 5v 1000ma”. A larger current output (ma or amps) than the factory charger is OK because it is up to your phone to decide how much it wants to draw. The ideal output is equal to the output on the factory provided charger. A higher output charger will not speed up the charge time unless the charger you used previously was lower output than the factory provided charger.
The output is always printed on the side of the part that plugs into the wall. If it's not, don't use it. Chargers without labels are manufactured in a place with extremely low standards and tolerances (China) and could damage your device and burn your house down. But just because it had a label doesn't mean it's good quality. Always know that your charger came from a reputable manufacturer.
Another reason to buy good quality cables is for thicker wire enamel. This is the (usually) black plastic that surrounds the cable- the part if the cable you can see. While a good quality cable usually appears thicker, is not only because the charging conductor is (sometimes) a thicker gauge, it probably also gas thicker enamel. This helps prevent damage from nicks and other wear. Also the shield of the wire which helps prevent electrical interference will be thicker.
Like the OP said, it's always great to identify the conductor size when buying a cable. A poor quality cable could appear to be higher quality by just making the plastic enamel thicker instead of increasing the size of the (more costly) copper conductor. The difference in thickness could appear about the same as the difference between a USB 1.0 cable and a USB 2.0 cable..
1. the USB specification has two different modes that are available to devices.
There is data/charge mode and charge only(aka:fast charge)
The charger has to have two of the four wires shorted out in order to tell your phone to use fast charge, and a lot of cheap chargers do not do this.
Also, cheap cables sometimes leave out the data wires completely, (or use really weak wires for data that break quickly) which can prevent that communication from happening.
Tldr: buy 2.0amp capable chargers and larger gauge cables, or expect slow charging.
2. "Fast charge" is not always fast. It's just possible to go faster than standard USB.
Standard USB charges with up to 500mA. "Fast charge" is typically up to 1000mA, but I've measured way below 100mA on cheap chinese ones.
Just because your phone says "fast" or "AC", it doesn't have to be faster than USB. You need a good charger and a good cable.
The 2 usb modes are 500mA, and 2000mA.
If your charger is labeled for fast charge but doesn't supply (at least) 2000mA, then it is not designed to spec.
If it's not designed to meet the USB spec, DON'T USE IT. (for the layman, it has to have passed testing to legally use the "USB certified" logos. )
> The 2 usb modes are 500mA, and 2000mA.
When we say "fast charge" here, I'm assuming DCP (Dedicated Charging Port) according to Battery Charging Specification 1.2, which basically says 0.5-5A. And above 500mA it's even allowed to go below 4.75V.
Which specification do you assume?
> If your charger is labeled for fast charge but doesn't supply 2000mA, then it is not designed to spec.
I have not seen a charger labeled "Fast charge", but the maximum current is stated. Some of the way too cheap ones does not comply with DCP, and don't even short the data pins.
There's also some that's expensive enough, and actually can supply more than 500mA, but also doesn't short the data pins to indicate DCP. I have not tested how well they comply with the other parts of the specification.
Note: "fast charge" is the term used to describe DCP charging (data disabled) on android devices.
You are correct that the BC 1.2 revisions of the 2.0 spec show a suggested maximum allowed current of 5 amps for certified DCP host devices.
The required operating range for the DCP spec is 0.5amp to 1.5amp @2-5V. CDP is 4.75-5v up to 1.5amps.
Meanwhile, the Maximum allowed load for a single portable device to pull is 1.5amps. (section 4.6.1)
DCP ports have no maximum current load set by this spec, in order to allow port/host device designers to provide sufficient current to charge multiple devices from a single port.
The spec still caps out at 1.5amps for a single device charging from DCP.
USB Chargers rated for less than 2amps of available current are not sufficient to provide a constant charging source for a 1.5amp device to charge at full speed.