# Can I use a power adapter from one laptop on another laptop?
**URL:** https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148
**Category:** Factual Questions
**Created:** [June 23, 2020, 12:20am UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148 "2020-06-23T00:20:37Z")
**Posts on this page:** 6
**Page:** 2
### Author:  [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)
#### Post date: [June 25, 2020, 9:01pm UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/21 "2020-06-25T21:01:06Z")
I don’t know.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [June 26, 2020, 12:52pm UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/22 "2020-06-26T12:52:02Z")
Since USB is all 5 V, the chargers differ by their current ratings. If your device complains that a charger is inadequate, it means that the charger’s current rating is inadequate: Either it’s not advanced enough to be able to negotiate currents higher than 1 A, or it can negotiate but knows that it can’t safely deliver as much as the device would like.
Most likely, if you plugged a computer into a charger meant for a phone, it would complain about it and charge only extremely slowly. You might even need to turn it off for it to charge at all: It might otherwise be getting less power from the charger than it uses for standby. On the other hand, plugging the phone into the computer’s charger would be hunky-dory all around. In no event should anything be damaged, provided everything follows the standards.
Of course, that’s a non-negligible “if”. There are a fair number of devices that use USB-shaped plugs but which don’t follow the USB standard. Caveat emptor.
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### Author:  [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)
#### Post date: [June 26, 2020, 1:35pm UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/23 "2020-06-26T13:35:12Z")
> [@Chronos](#):
>
> Since USB is all 5 V, the chargers differ by their current ratings.
That may be true of USB 2.0 or 3.0, but the computer chargers I mentioned are USB-C, which can carry higher voltages and wattages.
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### Author:  [@Melbourne](https://boards.straightdope.com/u/Melbourne)
#### Post date: [July 24, 2020, 12:43am UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/25 "2020-07-24T00:43:27Z")
> [@Dewey\_Finn](#):
>
> That may be true of USB 2.0 or 3.0, but the computer chargers I mentioned are USB-C, which can carry higher voltages and wattages.
But the part where you said “USB-C is a standard just for the plug and cable” wasn’t informative. PD (as used by a USB-C charger) is a standard protocol, negotiation and set of “Power Rules” which define a set of voltages and current, backward compatible with USB and BC 1.2 signalling.
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### Author:  [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)
#### Post date: [July 24, 2020, 12:46am UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/26 "2020-07-24T00:46:11Z")
I don’t think I’m the one who said “USB-C is a standard just for the plug and cable”.
> [@CookingWithGas](#):
>
> USB-C is a standard just for the plug and cable; the voltage and current can vary based on the charging device. The chargers are not interchangeable. I have a few chargers with USB-C plugs, but if I don’t use the one that came with my phone, the phone shows a warning that it is charging slowly and recommends to use the OEM charger. It works, but that is not the same as being generic.
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### Author:  [@Melbourne](https://boards.straightdope.com/u/Melbourne)
#### Post date: [July 24, 2020, 12:47am UTC](https://boards.straightdope.com/t/can-i-use-a-power-adapter-from-one-laptop-on-another-laptop/912148/27 "2020-07-24T00:47:56Z")
> [@CookingWithGas](#):
>
> IANAEE but this is probably true. A 5% voltage variance may be OK. (A higher voltage would probably be more risky than a lower one.)
A simple low-drop-out switching regulator will burn out if fed a low voltage. It will draw more current, which will pull the supply voltage down, so it will draw more current, which will pull the supply voltage down — until it exceeds it’s own current rating and burns out.
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