USB to 2.1mm DC Booster Cable - 12V

This cable is kinda fascinating - it has an integrated boost converter, so you can plug it into any USB port (from a computer, battery pack, etc) and it will give you a higher DC voltage!
It's a handy way to power 9V powered devices with a 2.1mm DC barrel jack from a USB port.
These are rated at 500mA output, but you can go a little higher, we pulled 700mA and we got a little voltage droop but it worked fine. Probably best not to draw 700mA continuously though!
Here's our measurements for various current draws when we set our bench supply to provide a steady 5V voltage
5V Variant



Current
Output
Input
Efficiency


50mA
9.0V
100mA
90%


100mA
8.95V
205mA
87%


200mA
8.9V
410mA
86%


300mA
8.8V
620mA
85%


500mA
8.8V
1060mA
83%


700mA
8.8V
1550mA
80%



12V Variant



Current
Output
Input
Efficiency


50mA
12.4V
150mA
83%


100mA
12.4V
290mA
86%


200mA
12.3V
570mA
86%


300mA
12.2V
870mA
84%


500mA
12.1V
1500mA
81%


700mA
11.4V
2140mA
75%



So, overall there's a 85% or 90% efficiency (depending on the cable chosen) at low current draw that drops do about 80% at high current use. There's also a 3 mA quiescent current. Note that often times the USB port voltage can droop too, and in addition you may have power losses with any thin or low quality cables with high resistivity!
TECHNICAL DETAILS

Cable Length: ~1.2m / ~47"