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USB to 2.1mm DC Booster Cable – 9V

by Adafruit

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!


  • Cable Length: ~1.2m / ~47"