Underpowered laptop

I’ve been powering my laptop with a 90W cord. If I used a 65W cord, what would happen?

Look up the specs for the laptop: what does it require?

Says 19.5 volts but nothing about “W”, 65W vs. 90W, etc.

When I’ve done this with a Dell notebook system at work, either nothing happened or a message popped up before Windows booted warning that the AC adapter was insufficient.

By “nothing happened”, by the way, I mean nothing bad happened. The system booted just fine.

If the laptop requires more then 65W to actually operate then one of two things will happen:

  1. The battery will slowly discharge despite being plugged in. So after 2x or 3x the normal battery-only run time you’d have a dead battery. Or as other have noted, the laptop will completely refuse to take power from the cord and will instead discharge as if it wasn’t plugged in.

If you sleep, hibernate, or completely shut down the laptop before that happens it’ll recharge, albeit at a slower rate than it did with the 90W cord.

  1. The power “brick” in the cord will be overtaxed and eventually fail or overheat. Or it may fail promptly by blowing an internal non-replaceable fuse.

In general high quality OEM power cables will do Option 1 whereas cheap no-name knockoffs will do Option 2.

Without part numbers there’s no way to be more specific.

That’s one major branch of the decision tree. The other branch of the decision tree is “If the laptop does not require more than 65W to actually operate”, which might happen if the original 90W power supply was grossly over-specced for the laptop (like buying a laptop second-hand with a separately-purchased power supply, or maybe the manufacturer provided a power supply big enough for any laptop they sell in order to simplify their supply chain). In which case, nothing bad happens.

LSLGuy has the critical point identified: figure out the rated wattage required by the laptop and compare that to the 65W of the brick.