[HTC 10 Guides, News, & Discussion] lagittaja:
And I might just add to this conversation regarding the amperage rating of cables. Some of you probably already know this stuff but some might not.

It's basically the gauge of the wire and the length that dictates how much current (amps) you can pass through a cable.

The thicker the wire, the more current you can pass through it. With AWG, lower number = thicker > 26AWG is "better" than 28AWG.

The longer the wire, the more resistance will there be which will be affecting the voltage on the other end of the cable.

Let's do some math (well I'm gonna use a calculator but it's basically just math).

I have a HTC One M7 A-microB cable here, judging from it's thickness and flexibility it's 28AWG.

It's length is 94cm not including the connectors. The charger is 5V 1A.

The maximum (target) voltage of USB 2.0?/3.0 spec is 5V and it allows a variation of +5%/+5% (5.25V) and -12%/-11% (4.40V/4.45V)

So, what happens when you draw 5V 1A through that 94cm 28AWG cable?

Assuming the charger outputs 5.00V > the voltage drop is 8% across the cable which means that the voltage at the other end of the cable is 4.60V

Certainly within spec. Although this is just the cable, conductors themselves play a role and then there's the condition of the cable and so on.

But that 8%/4.6V should be really close.

So, what kind of wire gauge do you need for higher currents at that same 94cm?

With 28AWG and 5.00V charger you can just barely get away with 1.3 amps.

Voltage drop would be 10.4% or 4.48V at the end.

That's why we've seen many 5V1.2A phones/chargers.

Manufacturers want to go as cheap as possible and higher the gauge, the less copper you need > lower cost.

So how about those really higher currents?

With 5V2.4A the bare minimum is 26AWG which is at the edge of the spec, 4.40V so 25AWG or 24AWG is a better choice which would be 4.52V and 4.62V respectively.

With 5V3A the bare minimum is 25AWG which is at the edge of the spec, 4.40V so 24AWG is a better choice which would be 4.52V.

So here's the million dollar question. Do most of these 5V chargers output 5.00V or ~5.20-5.25V? The spec allows for +5% so it would only make sense to make use of that. I don't have a spare USB cable I could gut right now to go and check few of my chargers..

Using 5.25V...you could get away with

5.25V1.0A = 31AWG 4.45V (instead of 29AWG 4.5V)

5.25V2.4A = 27AWG 4.49V (instead of ~25/26AWG 4.42V/4.4V)

5.25V3.0A = 26AWG 4.49V (instead of ~24/25AWG 4.52V/4.4V)

Charging 24AWG/94cm cable at 5V3A vs 5.25V3A > 13.56W and 14.31W respectively, or +5.53% more power.

Too long, didn't read:

If you want the best possible charging speed and efficiency: buy the cable with the thickest gauge possible and the shortest you can deal with.

The gauge is basically limitless but connectors (microUSB or C) do have their limits on how big wires you can shove into them.

From my understanding, 18AWG is basically pushing it while 20AWG is actually the thickest the Type-C spec lists in their "typical wire gauges for reference only" tables.

24AWG cables should be abundant and would be the thinnest I would go for. Thicker the better but there's of course downsides.

The thicker the gauge the sturdier it is and not so flexible. So it makes sense to have a dedicated charging cable.

Thicker gauge > larger bend radius = it's not so flexible and if you bend it too much you can damage it.

If the manufacturer or website or the packaging doesn't tell you the gauge, I wouldn't buy it.

If you're looking at a cable in the store and the cable itself doesn't have the numbers printed on it (or on packaging, website etc), I wouldn't buy it.

So how much benefit from thicker or shorter cable?

Assuming "15W of power" eg. 5V3A

25AWG 94cm = 4.40V * 3 = 13.20W

24AWG 94cm = 4.52V * 3 = 13.56W

22AWG 94cm = 4.70V * 3 = 14.10W

20AWG 94cm = 4.81V * 3 = 14.43W

Going from barely enough 25AWG to 20AWG is almost 10% more power.

You can directly translate that into faster intial charging speed before the charge enters the constant voltage mode, like uhm 0%>~90% and 90%-100%.

Going to a 50cm cable

24AWG = 4.75V * 3 = 14.25W

22AWG = 4.84V * 3 = 14.52W

20AWG = 4.90V * 3 = 14.70W

Or if you want a 2 meter 5V3A charger, you need 21AWG to make it work, voltage would be 4.5V, so yeah it will work but it's slower than a shorter cable.

P.S.

Also yes, I know. If power is kept constant when voltage goes up > current goes down = relative voltage drop also goes down.

So with 12V 1.25A the difference between a 94cm 20AWG and 25AWG is a negligible 1.5%.

But I decided to focus on 5V which is a nice number and happens to be the USB spec and so on.