Charge older Samsung phone (with Quick Charge 1.0 technology) at full rate

Question

I own a Samsung Galaxy S Relay, which is an Android phone a few years old. It's sort of similar to the Samsung Galaxy S III, but it also includes a slide-out physical keyboard.

Like the Galaxy S III, it supports Qualcomm's Quick Charge 1.0 technology — a technology which Qualcomm admitted was "little-known". I owned the phone for a long time before discovering that it supports Quick Charge 1.0.

What type of charger do I need in order for the phone to charge as fast as possible? Do I need a charger with some special certification or features? Or, is there any other way I can charge the device as swiftly as possible?

Answer 1

Qualcomm marketing manager PJ Jacobowitz writes:

Quick Charge 1.0 makes all this is available to the user with existing USB charging accessories — no new cables and wall chargers to buy.

OK, so I don't need a charger with a special Quick Charge logo or anything. Good.

Still, surely an underpowered charger won't allow the phone to charge as quickly as possible. OK; what charger do I need?

Android Authority contributor Rob Triggs adds:

Qualcomm’s Quick Charge 1.0 technology was designed to maximise charging efficiency for up to 10 watts of power, by allowing for a maximum current draw of 2 amps through a standard USB adapter and port voltage of 5 volts.

Though Android.SE user "TurboFool" warns:

Nearly all chargers that advertise themselves as 2.1A are optimized for iProducts, which require a different grounding scheme in the charger to reach their full speed, and that same scheme limits Android devices to 500mA. So counter-productively you'll find that most 1A chargers will charge your Android device faster than 2.1A chargers. [...] The way around this is to buy a charger that's specifically designed to adapt to whatever device you're using.

Ah. So I'll need a charger which is able to provide 2 amperes even to my device. (Related question: "How can I tell how many milliamps my phone is drawing from the attached charger? Preferably without having to use a multimeter.")