usb amps

Discussion in 'General Electronics Chat' started by aac9876, Feb 26, 2012.

  1. aac9876

    Thread Starter Active Member

    Dec 9, 2006
    I have a cheap car inverter that has AC and DC output. The instructions dont say how much amps the USB dc 5v out has.... I have a Fluke meter and it has DC amps.
    Where do you put the leads to check a USB plug for amps..????
  2. BillB3857

    AAC Fanatic!

    Feb 28, 2009
    If it is the Black & Decker inverter, it uses a series resistor with a zener to ground to give you the 5 volts. It isn't a physically large zener so I wouldn't expect much in the way of current out of the USB connector. Just had mine apart but didn't check the resistor value. It does get warm to the touch with a 15 volt input.
  3. wb2vsj

    New Member

    Feb 19, 2012
    USB from a PC is about 500mA - that's a pretty standard value. I would hazard a guess that's about what it puts out.

    I wouldn't plug an Apple iPad into it, those iPads need about 1Amp.

    If you want to really test it, here are the pin outs for a USB port
  4. aac9876

    Thread Starter Active Member

    Dec 9, 2006
    the rep said its 1 amp. Its a Cyberpower BU150 car inverter. It works good but noisy fan.