I want to use a USB cable and an AC to DC adapter as a supply to my electronics project. I plan to connect the USB cable to the USB port on the AC to DC adapter then I will cut the other end of the cable. There will be 4 lines in the wire namely 5V, Gnd, D+ and D-. I will use the 5V and Gnd lines as a power supply. However, based on my research, if you cut the data lines of the USB cable, the 5V and Gnd will supply less current that it is intended to because it won't be acknowledged by the connecting end that it is used for charging (ex: connecting the USB cable between a phone and a USB port of the laptop). Will this be true even if I connect it to an AC to DC adapter?


1 Answer 1


Barring specialty chargers such as USB-C power delivery standard or Qualcom quick charge standard, regular USB chargers are dumb. They have no idea what is connected to them. They will supply up to the rated current if the load demands. It is up to the device to detect what kind of charger it is connected to and decide whether it will pull full current out of the charger.

  • \$\begingroup\$ I'm only using a USB Type A cable. I connected it to an AC to DC adapter that supplies 5V and 2A. Meaning if I cut the data lines and use the Vcc and Gnd pins, I can still get that power from the adapter? \$\endgroup\$
    – LinkedRom
    Mar 6, 2019 at 11:44
  • \$\begingroup\$ @LinkedRom Yes, barring the charger being specialty. You can always try it first to test it. You would just have to hack up a cable. \$\endgroup\$
    – vini_i
    Mar 6, 2019 at 11:45
  • \$\begingroup\$ Thanks. I want to test it using a multimeter but I currently don't have one today. \$\endgroup\$
    – LinkedRom
    Mar 6, 2019 at 11:52
  • \$\begingroup\$ You can't test charger current with a multimeter. \$\endgroup\$ Mar 6, 2019 at 14:27

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