Hi how can i emulate USB power?

I want to make this box which can get power from usb portable, so i know my way around a usb cable and i could just cut one but what battery configuration would i need?
THank you very much!

bmlbytes7 years ago
The USB 2.0 standard says that a single device may draw 5 volts and up to 100 mA from a computer. So you really need 5 volts worth of batteries. 100 mA is not a lot of draw, so even small batteries should work for a while. You could put 4 AA, AAA, C, or D batteries in series, with a 5v regulator (like $1 from radio shack) or a single 9v with a 5v regulator. Most devices will probably work with the 4 AA batteries without a regulator, because the 6v is not much different than 5v. Now there are a few exceptions to this. Certain devices use special USB ports, or need certain computers to charge. If the cable looks like it has 2 ports on one cable, or you have a device known to need special USB ports, you may need a bigger battery to keep the device running. For example, the Apple iPad needs 1000 mA. That is 10 times more power than a standard USB port.
amishra123 (author)  bmlbytes7 years ago
urm the usb cable which i connect the device with is one of these ( http://media.snipesoft.net.nz/pictures/c3312eb4-f07f-bca9-e9d9-44c756fa2579-10.jpeg ) i dont know if thats what you meant or not? When you say voltage reg do you just mean as in a chip?
lemonie7 years ago
You need 5V. 4 NiMH might do it What are you wanting to power with it? L
Re-design7 years ago
3 - 1.5 volt batteries in series would run most usb stuff.