12v USB Charger problem

[mikeboatboy]

Hello friends, I recently bought these 12v USB chargers, and was testing them out yesterday with my 12v 10-amp power supply. For some reason when I plug my phone into the USB charge port it only draws 0.3 amps @ 12v which I'm guessing gets converted to about 0.8 amps @ 5v, which is barely enough charge to keep the phone going, much less charge it. Does anyone have any idea why this is happening? Thanks, I'm a total newbie to electricity. I tested both usb ports and results were the same.

 

[DarrylG]

Here is a thought: I see these are quick charge 3.0 specs. That has requirements that would greatly exceed your 5v .8 amps, but possibly the USB cord or your phone doesn't support or need the higher voltage/amperage draw. Or your phone was mostly charged already... Or settings are set to slower charging.

I believe the max output power of QC3.0 is 36 watts (12 V × 3 A). But it only pulls whatever input it needs for the specific task.

 

[mikeboatboy]

That's interesting. Why would the phone pull more juice when plugged into the wall charger vs these little usb chargers? It's not maxing out the usb charger by any means.