[Moto Z Accessories] rczrider:
Here's more information than any of you probably care about, but I'm tired of seeing the same misinformation and confusion being thrown around (not just in the Moto Z forum, but in a bunch of others, too).

That's not true. Case in point: my ZTE Axon 7 and LeEco S3 both use QC 3.0 and both are USB-C. The common confusion comes from using "USB-C" (a connector) and "Type-C" (interchangeably used to refer to the connector and the power specification) incorrectly. Clarification below.

This is mostly true. "TurboPower" is the stupid name Moto uses to refer to the Type-C power specification. Actually, I'm being unfair: it's confusing that they called it "Type-C" in the first place and Moto took the opportunity to market the spec as their own thing.

Before going any further, let's use a common analogy to make the relationship between, wattage, voltage, and amperage easier to understand in broad terms. Wattage is the amount of water going through a pipe. Voltage is how fast that water is moving and amperage is the size of the pipe. 15W is 15W, but you can get there by having a tiny pipe (1A) with water moving really fast through it (15V) or a really big pipe (3A) with water going more slowly through it (5V). They both move the same amount of power, but in different ways. Got it? Good.

Anyway, Type-C has a fixed voltage and maxes out at 15W (5V@3A). Quick Charge 1.0 does only 10W (5V@2A), 2.0 does 18W (5/9/12V @ 3.6/2/1.5A respectively), and 3.0 does 18W with varying voltage (3.6-20V) and amperage (5-0.9A) to match. That is the advantage of QC over Type-C: a higher voltage can (usually) be run through those old and cheap USB cables without issue since voltage tolerance is determined largely by the phone and the charger. As long as the amperage doesn't exceed the capacity (gauge) of the wire, higher voltage is fine.

Amperage, though, that's what causes non-compliant or crappy cables to burn up. Really old or especially cheap cables can handle 1A max (heck, if they were built to spec, only 500mA for USB 2.0), but most cables of reasonable quality can handle 2A without much issue. They tend to use lower gauge (thicker) wires and should *not* feel warm at all when using it to charge. Some manufacturers (Samsung, for example) used to disable data on their USB cables and use it for additional amperage capacity, which is why you would occasionally buy a phone with a cable that wouldn't work for data transfer in the computer but would charge your phone just fine.

Moving on. Technically, QC 1.0 and QC 3.0 do not violate the Type-C power spec. QC 1.0 because it can't exceed it and QC 3.0 because it's variable. That said, QC 3.0 (and possibly QC 1.0, I don't know) require protocol negotiation; if that negotiation is lacking (in the case of the Moto Z), it's going to default to a "safe" charging rate (around 5W, plus or minus some). Your QC 2.0 does technically violate the Type-C spec because its voltage and amperage rates are fixed: you can get 5V at up to 3.6A. The "up to" bit is the important part. I have seen in various threads folks claiming their non-QC 3.0 phones will work with QC 2.0 chargers just fine and it's probably because the amperage tolerance is there (ie. it will actually allow 3.6A, violating spec) or it gets throttled (ie. sticks to 3A, keeping to spec).

All Type-C and USB-PD compliant devices are picky about the charge specs, not just the Moto Z. Or, at least, they're supposed to be for the reasons outlined above (namely the amperage). QC devices are less picky because it frequently uses higher voltage, which we established above as being much more tolerable for cables of varying quality.

Your cable melting and glowing is to be expected when you push 3A through a cable that likely can't handle more than 2A or so. Your phone charging port survived because it's designed to handle 3A.

I'm not entirely sure about which pins do what on a USB-C connector, but you're right in the C-to-C is the only connection that (should, according to spec) support Type-C and USB-PD (Power Delivery). The rate is negotiated via the USB Power Delivery 2.0 "power rules", which define four acceptable voltages (5/9/15/20) and variable amperage (0.1-5) to obtain charge rates as low as 0.5W and as high as 100W. "Type-C" is part of the Power Delivery spec, but is usually limited to only the 5V rule. I'm fairly certain the Moto Z does not support anything past the first level power rule, which is why you likely won't find the Moto Z to charge significantly faster with the TurboPower 30 included with the Moto Z Force than it does with its original TurboPower 15 charger. No clue as to whether that's a hardware or software limitation.