I have an HP Elitebook 8440p with Windows 7 Ultimate, i7 Processor and 8 GB RAM.

For the last couple of days, when I plug-in my laptop for charging, the CPU usage shoots up to 100% and remains there for around 15 minutes. No offending process shows up in Task Manager/Process Explorer but the laptop is practically unusable for that time. The CPU usage becomes normal when I remove the power cord but shoots up again when plugged back. This is happening with different power adapters/wall sockets so it might not be a faulty adapter issue.

Why is this happening and any pointer to resolve this issue?

  • Please capture a trace using the Windows Performance Toolkit (see left side, it tells you you can get the toolkit from the Windows SDK and how to capture) and share it with us (or look into it yourself) such that we can pinpoint any non-hardware issues. Feel free to ping me at the chat with @Tom if you want more interactive help. – Tamara Wijsman Mar 19 '12 at 8:15
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    The task manager has to show something.. 100% on an i7 - seems like maybe some HP software is going into a loop trying to do something clever...but fails.. as usual. try safe mode and see if it happens. Its going to be some software I bet you! – Piotr Kula May 3 '12 at 16:20
  • I've the same problem now with a HP ProBook 4710s. I start the Taskmgr under Win7 looking for CPU-Usage. I've plugged in the original HP-Powersupply. CPU is on 50 to 100% (svchost.exe). Plugged off (Akku on): 0-1% on IDLE-Time. ...Plugged in a similar Dell PowerSupply: 0-1 % Viola. The Power-Setting for CPU-Cooling Policy does not work for me. I'll replace the PowerSupply. – user237601 Jul 12 '13 at 8:01

It might be that Windows does backup or hard drive scans while the power cord is plugged in, so look into back up management too see if there's something there. You could try booting the computer in fail safe mode to minimize the programs loaded and see if the problem persists.

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Take a look at All Programs, Accessories, System Tools, Task Scheduler. For each task listed on the left, look at the Conditions tab. Do any tasks have the following options ticked?

Start ths task only if the computer is on AC power
Stop if the computer switches to battery power

You'll probably need to Task Scheduler as administrator to manually remove any tasks.

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  • This is likely your culprit. How are you so sure? You've not done any prior analysis... – Tamara Wijsman Mar 19 '12 at 8:12
  • Fair call. More accurately, "This is the first place I'd look." – Hand-E-Food Mar 21 '12 at 0:22

Turns out it was a hardware issue. After I replaced the laptop battery, it started functioning properly.

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We were having the same problem with some of our devices. At least a solution for us was to remove the second travel battery! Explanation: The second battery covers some parts of the CPU ventilation slots. This leads to increased temperature of the CPU which then leads to scaling down the frequency!

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HP laptops come with a software to switch performance when plugged in or when running on a battery.

It switches to dedicated graphics when plugged in and switches back to on-board graphics when running on battery.

There could be a software issue.

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Had the exact same problem. 100% cpu usage when unplugged.

Try this. Go to power options and change the processor cooling policy to Active (if it is passive) in both balanced and in power saving mode and in both On battery and Plugged in options in windows 7.

No 100% cpu utilization shouldn't come to picture

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  • This seems to have solved my problem. If anyone has some explanation/documentation on why this setting is causing the 100% CPU load, I'd be willing to read it. – Otiel Jul 17 '15 at 12:33

I have the same issue with one power adapter, while the laptop works properly with another power adapter.

When the slow-down occurs, I can see that the maximum frequency shown in Windows Resource Monitor is only 10%, and will not rise even if the CPU load is at maximum.

My best guess is that the laptop decides to limit maximum frequency for some hardware reason, such as faulty battery or power supply.

This article has the same conclusion: http://www.itwriting.com/blog/985-hp-laptop-go-slow-caused-by-power-supply.html

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My EliteBook has the same problem with these symptoms:

  1. When AC power is plugged in, the CPU goes up to 100% even with no processes running. It takes a very long time to shutdown or start Windows.
  2. When AC power is unplugged everything works fine. CPU swings up and down again.

In my case the AC apdater is defective. When I use another adapter, the problem is gone.

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