This is the mini-adjustable regulated power supply with nice clear acrylic casing. It cost around 5 USD to 7 USD and it comes with voltage and current indicator display screen. I bought it to test small circuit especially Joule Thief current draw and min/max voltage supply.
However I was thinking that since the voltage can be adjusted why not try to charge a smart phone using it. And so to my surprise when i tested charging Samsung Galaxy A5 phone using 6 x AA batteries approximately 8 to 9 volts and set the adjusted setting to 5 volt as per standard smart phone voltage charging the current draw is about 1 Amp and sometimes peak around 1.3 Amp which is way faster than the original manufacture phone charger.
The original Samsung phone charge adapter can only supply around 500 mA to 590 mA maximum on 240 Volt AC. So i thought this is an amazing device to share although the voltage adjust button aren't so smooth as i expected.
Think of the possibility what it can charge such as iPad, Samsung, iPhone, and other gadgets probably charging 12 volts battery. And you can use any batteries such as AA, AAA, palette/coin batteries, 9 Volt battery, 18650 battery etc. You have the choice to adjust the voltage flexibly.