Tuesday, August 18, 2015

Android Phone (Samsung Galaxy Note 4) Power Usage

I was playing around recently with my Android phone and decided to take a look at it's power consumption when charging from my laptop USB port.

While the device comes with a quick charge power adapter, my little USB power meter is not expecting to draw a couple amps from a USB circuit, so in the interest of not damaging it, I gave it a standard USB 2.x port as a power source.  As we can see it is quite hungry and draws a consistent 2.1 watts in this mode, with only about 75 mA headroom on a standard USB charging rate of 500 mA.  The device does not seem to change its power consumption when using the device while charging or allowing it to sleep.  The device uses the typical method of various sense resistor values between the USB pins to determine if the special charger is in use or a standard one to limit current draw to USB specifications.

When charging on the quick charger, I am seeing about 1.27 amps when measured with my multi-meter, but it seems to walk around a bit from about 1.0 to 1.45 amps.

Once the charger has brought the battery up to 100% charge, I put it back on my little USB power meter and find a much more respectable 43 mA current draw.  Again, it doesn't seem to matter if the display is lit or not.