Can I use a 5V 1A USB charger to charge a 5V 2A device?

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xtarflashlight
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Can I use a 5V 1A USB charger to charge a 5V 2A device?

Many users asked us, can I use a 5V 3A USB adapter to charge my XTAR VC2 charger (requires 5V 2.1A)? Or can I use a 5V 1A phone charger to charge XTAR 5V 2A charger, or vice versa? I always receive these kinds of questions. So many users want to know what happens when they use the wrong charger specification.

There are two points you need to know.

Firstly, the Voltage supplied by the USB power supply must exactly equal what your device requires. Or some damage may occur to either.

Secondly, the Current of the USB power supply should equal what the device requires or be larger. If it is smaller, the device may charge slow or may not charge.

A device will only draw the current it needs. Under the same voltage, if your device is rated at 2A, it will only take around 2A from a 3A output of the USB power supply, leaving a 1A of headroom. So, as long your device needs less power than the USB power supply can provide, no need to worry.

If your device is rated at 2A and your USB power supply gives a maximum of 2A or even can’t reach 2A, it means it is working at 100% and will heat up. Your device will either charge slower or just drain the battery slower (if battery powered) or refuse to work (not enough power to operate).

Any more ideas or suggestions? Please comment below.

Forsythe P. Jones
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Necro’ing old thread because it asks a relevant question and then doesn’t answer it. What DOES happen if I use a 1 amp charger to charge a device that wants 2 amps? A properly designed device is supposed to negotiate power draw if it wants more than 100 mA, but most stuff doesn’t. So I see 3 possibilities if you try to charge a device that wants more power than the charger can supply:

  1. It charges fine, just slower than if you used a 2 amp charger. This is perfectly ok and I’d hope the device is designed to ensure that this is what happens.
  2. It doesn’t work, e.g. sits there without charging, but isn’t damaged. Not great but no real harm done.
  3. Device is damaged, catches on fire, stuff like that. I very much hope this doesn’t happen.

I am reminded of this question because I have a Ryobi lantern powered by an 18v tool battery, that has a USB outlet for charging phones, but it says 1 amp maximum and if you try to draw more than that, damage can result. That is crazy, imho.

Lightbringer
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Old/original usb was supposed to be limited to 500mA unless negotiated higher (to allow “dumb” doodads to still work, like usb lights, fans, etc.).

I use an old laptop to charge, eg, 16340s, at 500mA max.

Then again, I got a “lipstick” powerbank that I’d use to speed-charge my old tablet ‘cause it’d dump as much current as sucked down, to the point of getting quite hot (powerbank and plug/socket). LOL

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Forsythe P. Jones
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You were supposed to negotiate power draw above 100ma, up to a max of 500ma, if I have it right. In fact ports could pretty much all supply the max 500ma and it was usually ok to use it. Next thing after that is it started going way over 500ma…

Lightbringer
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Yeah, sumpin’ like that. Don’t think I ever had anything actually being limited to 100mA, though. Guess they were designing ports that were rather “generous”.

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Patu
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Quote:
If your device is rated at 2A and your USB power supply gives a maximum of 2A or even can’t reach 2A, it means it is working at 100% and will heat up.
If that is legit then that is very useful to know.