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This question already has an answer here:

Two questions on points not covered in either of these two threads about AC adapters:

Choosing power supply, how to get the voltage and current ratings?

Reading and understanding electrical specs on laptop AC adapters

1) Watts aren't mentioned. Is it okay to replace a 65w AC adapter for a laptop computer with 90 or 120w?

2) Voltage: It says an adapter must not have higher or lower voltage than a device's specification but it doesn't say how much higher or lower, e.g. whether a difference of 1 volt out of 20 is a rounding error, or physically meaningful. Specifically, is it okay to replace a 20v adapter with a 19v one, for a laptop computer?

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marked as duplicate by Tom Carpenter, winny, Charles Cowie, Voltage Spike, Harry Svensson Jul 6 '18 at 16:31

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ They tell you that voltage is most important. They also tell you that you have to deliver at least as much current as needed. More is OK. Since power is the product of voltage and current, you see that you need a power supply of the correct voltage, and the same or higher power rating. \$\endgroup\$ – JRE Jul 6 '18 at 11:10
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    \$\begingroup\$ 19V is often close enough to 20V ... but not always. For something expensive like a laptop, would you risk it? I wouldn't. \$\endgroup\$ – Brian Drummond Jul 6 '18 at 11:30
  • \$\begingroup\$ @replete ahh, my bad, misread the question as wanting to replace a 90W supply with a 65W supply. 1) Rated power needs to be >= required power, no problem being higher. And 2) Maybe. \$\endgroup\$ – Tom Carpenter Jul 6 '18 at 12:49
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Is it okay to replace a 65w AC adapter for a laptop computer with 90 or 120w?

1) Yes. As long as the wattage is higher, it's fine.

Specifically, is it okay to replace a 20v adapter with a 19v one, for a laptop computer?

2) It depends on the device, but it will probably work. Devices generally will not be damaged by a voltage that's too low. They just may not work correctly.

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