[bombela]

Recently I bought and returned to amazon around 5 different USB SD card reader.

Turns out they all used the exact same USB hub/combo card reader chip.

This chip burns enough power at idle to heat up almost 30°C above ambient.

After enough testing I found out that on many motherboards, you can turn on USB power saving per port. This effectively get the device to consume almost nothing at idle.

But this only works on those ports. Anything indirect; for example apple usb-c to USB + HDMI dongle; the device would be burning power and heating up.

Same behavior on all three major operating systems. What matters is the motherboard ability to control power to a single USB port as far as I can tell.