The fastest way to charge the Nexus 6P or 5X is with the included type C (reversible connector) USB charger, generically rated at 5V 3Amps. Don’t expect a steady 3 Amps out of this, but the upper limit of what you get out of this is 3 Amps.

There are a bunch of quick charging standards, Some (Apple) supplying 9 Volts through a type c connector. But you wouldn’t try using that, would you? Something that DOES happen is using a phone rated for this standard and connecting it to an Apple laptop with this connector and the phone tries to draw too much current from the laptop and ruins the laptop port. That DOES happen. But you wouldn’t try that, would you?

To protect against this sort of thing most a to c cables have a built-in 56k ohm resistor to signal a limiting current (by voltage on the USB pin for that) to talk to various kinds of chargers or USB ports. This resistor can also directly limit current from relatively dumb interfaces.

So, I’m reluctant to just plug ANY c type charging supply to the Nexus 6P.

I have been told that any Qualcomm Quick Charger, either type 2 or type 3 is safe as long as the a to c cable has a 56k ohm resistor in it (which is standard). This is why you’ll often see a reference to this or the cable “conforming to IF standards”. There are copyrighted symbols for standards conformity, also. All this stuff will get standardized, but it’s still a bit of the “wild west” out there with a few companies breaking the rules to get a rave review at how fast their charger is. But you wouldn’t just buy anything, would you?

Needless to say, I was a little wary of a type c charger (with a c connector at BOTH ends of the wire, claiming to be a 5 Volt 3 Amp smart charger.

I bought one from Amazon for $15 including a c to c charging cable. The company is Yootek. It works identically to the very good charger that comes with the Nexus 6P (or the similar one that comes with the Nexus 5X). This is a big deal for me, to find a cheap and very rapid charger

.Here’s how to read the screen capture of the Google battery display in Android 6.01 (Marshmallow) Nexus 6P. Yesterday the battery was charged to the top. At around midnight the phone was left alone and went into a very slow usage mode (almost a flat line). At about 11 AM, the phone had about 30% charge (!) and was operated (iHeart radio) to about 17% charge. It was put on the Nexus (supplied) rapid charger and reported “charging rapidly” and it would take about 1:48 to be full. This charging rate (at 17%) was reported at about 2.5 Amps by the “Ampere” app, which is a “guesstimate” and sort-of works okay on the Nexus 6P. (Results vary, because it’s just a guess, based on voltage change and reported battery capacity.) The gray almost-vertical line is a guesstimate also, based on the voltage change over a few minutes. The steepness of the line is how fast the charger is, if you get my drift. 

The new Yootek type c charger arrived and was plugged it in using its supplied c to c cable. The screen capture is on the right. The Ampere app screen got capture got lost because I forgot to save it. The results were, in my opinion, identical. The rapid charging message was displayed and the current was similar.  After a few minutes the charge was at the 40% level and the charge rate guesstimate was the same slope and the “time left to full” was around an hour(!).

I would rate the Yootek charger as identical in effectiveness and quality to the OEM charger.

I also tried a variety of cables and chargers and would rate the charging speeds (that I could test) in this order of speed:

Using a “real” USB type c USB 3.1 computer port (you don’t have one), with a c to c cable, sort-of quick, sometimes going faster than 2 Amps, based on the Ampere guestimate, but not reported as “charging rapidly”.

Using a USB 3.0 type A port on the computer (few people have this) and a USB compliant a to c cable would charge at about 800 mAmp (.8 Ampere), which would surely get the job done.

Using the same port and a a to micro USB “charging cable, the kind you probably have, and an Anker (very small) micro USB to c adapter on the end the charging rate was a little slower, around 400 to 500 mA.

Don’t take the current (amperage) readings as anything more than an estimate for comparison, similar to the mph estimates on a car sticker. Disregarding the exact numbers, the two type c chargers did exactly what was promised and would charge the battery from bottom to top in about two hours. Also the charging rate when the battery was low was really rapid, charging to 80% in something like 20 minutes. And that should probably get you trough the day. The full charge should last a day and a half.

For type A connectors there is a great in-line amp and volt meter, which you could use on regular chargers to compare quick chargers, including Qualicom Quick Charge 2 and 3. The USB type c (c to c cable) labeled as 5V 3Amp, are reported as at least a little faster. Some say the preference is for the type 3. Some say the type 2 is not good enough.

There IS at least a slight difference between the Nexus 5X and 6P (different manufacturers). The 6P seems to display the “rapid charging” message based on voltage or current and the 5X seems to do some digital handshaking. I haven’t checked this, just noted it on a YouTube video about using quick charge 3 on each, that both worked okay, but 5X reported “charging” and 6P reported “charging rapidly”.  When an inline type c amp and voltmeter comes out for cheap, I’ll have better answers.

Charge on!