What amps do USB output?

[TheMidnightNarwhal]

Does it regulate to the device needs? I got a electric lighter and it says do not use with charger with above 1A

[Bananasplit_00]

USB from your computer? 2A i think

[samcool55]

Most usb ports are 1A.

Some USB 3.0 ports can be more, 2A is quite common.

On notebooks it's possible to have a few 0.5A ports.

 

But don't worry about it, pc usb ports are smart enough to not fry your devices.

[AresKrieger]

USB 2.0 is set to 0.5A max

 

3.0 is 0.9A

[gilm0re3]

Theoretically you should be safe no matter what you plug into. USB is fairly smart about now allowing more amperage than the device can take, but I could see how something like a cheap USB lighter wouldn't have the proper resistors or whatever to comply with the USB spec for safety. Especially since you are trying to charge a simple lighter it really shouldn't matter whether you charge off of a .5 or 1 amp port since the lighter won't be slurping power away like a phone would because it isn't in an always on mode like a phone. Newer phones usually can't do .5 amps simply because they are using more power by the phone being on and running the display than they are are taking in from the power brick. 

[BeatJ]

So normally a USB 2.0 can deliver 500mA max. and USB 3.0 can deliver 900mA max

 

[You_are_a_cunt]

Signal

5 V DC
Max. voltage    
5.00 (USB 2.0)
5.00 (USB 3.0)
Max. current    
0.5 A (USB 2.0)
0.9 A (USB 3.0)
3 A (type-C)
 

[mariushm]

The USB standard says usb version 2.0 should output 5v at maximum 0.5A , or 2.5 watts . The usb version 3.0 raises the power up to 5v at 0.9A  or 4.5 watts.

 

However, most motherboards have a lot of usb connectors so in order to save money on components, they don't implement power monitoring and limiting on each usb connector. Instead, most motherboards group up to 4 usb connectors behind a protection chip that monitors the power used and trips a virtual fuse if more than 2A of current is used (to protect the motherboard traces). So, all four in total could use up to 2A, or just one of those 4 could use up to 2A.

If the usb cable has thick enough wires, it's quite possible for a device plugged into your usb port to consume up to 5v at 2A , or 10 watts.

 

The electric lighter may have a very basic charging mechanism that doesn't monitor how much power the battery receives and just relies on the charger itself not being capable of delivering more than 0.5A to protect the battery. If this is the case, if you charge the electric lighter with a charger or from a usb port that is capable of delivering more than 0.5A, you may overheat or damage the battery inside that electric lighter.

 

[Unimportant]

I'd like to add that since the standard states that a USB2.0 port is limited to 500mA, most devices that use more then that look for certain voltages on the data pins of the USB port to check if they are allowed to pull full power or not.

 

Phone chargers and such have a resistor voltage divider network on the data pins of the USB port to supply certain agreed voltages on said data pins. The phone checks the presence of these voltages to determine if it is attached to a high current charger and can thus pull full power or attached to a pc and should limit to 500mA.

 

If this electric lighter is anything decent it might also make this check and refuse to work on a pc.

[Huntsman]

USB2.0 has a maximum of 0.5A no matter how you draw it. USB3 and above however, has a max of 0.9A without negotiating for more power packets. When properly negotiated, can draw up to 2.1A. These specs are assuming that the source USB is a PC. However, if we're talking about wall chargers, all bets are of. They will supply the max the hardware can provide.

 

By your description, your lighter must not have any over-current protection so it is best to plug it into a PC or a low current wall chargers.