Windows Fully Charged
When Windows says "Fully Charged", does it stop charging the battery and start using pure AC power? Or does it keep using battery but the AC keeps charging it? Or does it do something else?


It depends on the design of the laptop and the power demands. But basically, the battery will remain fully charged under all normal usage conditions. Whatever power the laptop needs will be drawn from the AC power source.


It goes off of AC power, you'll notice on a laptop if you pull the battery while it's charging the computer will stay powered on without any issues.

  • Sorry, so let me clarify because I don't fully understand your answer. When you say "off of" does it means it's running from AC power? Or it's not on AC power? Also, I don't see the point you're trying to make with your second statement about staying powered on. If you can clarify, I would highly appreciate it. Thx – Kevin Pei Dec 28 '13 at 20:13
  • This is false for many laptops. Without the battery, many laptops can't supply full power or can't adjust to the rapidly-changing power needs of a modern CPU. – David Schwartz Dec 28 '13 at 20:18
  • @kpsuperplane Sorry for the lack of clarity, I meant to it would be fully powered and function using only the AC power. The second statement was meant to give an example and serve as proof of the first statement. – user270595 Dec 28 '13 at 22:51
  • @DavidSchwartz That's never happened to me, but I don't use an Apple laptop so the issue is most likely that they just need a charger that supplies more amperage. Rapid changes in power requirments are not a likely factor in that senario there as long as it didn't try to draw more than the power supply could handle, which I assume is why the Mac's clock speed drops. I wouldn't say that issue applies to a large number of laptops because of that one link as it seems limited to Apple's products, but I've only used three or so laptops so far, so you could be correct. – user270595 Dec 28 '13 at 23:06
  • @Slowki Again, that's not true. The AC power adapter connects to the laptop with a long, thin wire that has a lot of inductance and capacitance. Even if the adapter can supply enough power, it may not be able to change the power it's supplying rapidly enough. Modern CPUs can drastically change their power requirements in a few nanoseconds. – David Schwartz Dec 29 '13 at 22:08

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