Laptop cahrge rate


I have recently bought a new battery for my HP Compaq nc6120 and experience a strange behavior. This is not new to me but I thought it was due to my old dying battery and did not worry before.

I run OpenSuse 11.0 and whenever I connect the AC adapter I find that it is charged at a very low rate or not at all.

The laptop is dual boot with WinXP so I could make comparisons. Here is what I have found using an Ammeter and looking at /proc/acpi/…/battery files:

  1. The power consumption of the laptop is roughly the same under normal office use under Linux and WinXP. I measured it with the Ammeter with Battery removed.

  2. Power consumption data under /proc/acpi/…/battery is fairly accurate under Linux (in Win I do not know where this can be found)

  3. If the battery is half charged then under Windows it starts charging the battery whenever the AC adapter is connected. Charging stops only when extreme load is placed on the laptop e.g playing back a video from file, copying data onto the disk, burning a DVD and copying data to the wireless network at the same time. In this case charging the battery under Windows is stopped as there is not enough power coming from the AC adapter. When charging the AC adapter always becomes quite hot, cooling back when trickle charging hits in or charging stops. So I can see normal behavior.

  4. Charging process is roughly the same when the laptop is switched off. It seems that the design of the AC adapter (65W) allows for normal office load use and full rate battery charging, which is a fair design.

  5. However, under Linux I can virtually never see the battery charging. Kpowersave only indicates battery charge when the Laptop consumes virtually no power even then the cahrge rate is slow, the time remaining until fully charged is either 0:0 / indicating infinitely long time or well over 8 hours under minimal load (no activity, LCD dimmed to minimum). From within Windows 4 hours is the max I have ever seen under normal office load. The AC adapter never gets hot, it always remains just slightly warm as confirmed by the Ammeter too.

I conclude that Linux fails to utilize available power from the AC adapter. Has anyone out there experience with this? How do these things work and how can I adjust settings?


All I can say is, my Lenovo ThinkPad works beautifully. Although I do have Vista, I just never use it, but the little I have gives me no reason to think it is any better than Suse, in fact if anything it would be to the contrary in most respects.

If you have kde4 you could try powerdevil. But you need to remove powersave to use it.

Hi Doma,

Hey - nice issue! Very interesting. And you have certainly taken appropriate steps to isolate it, use the ammeter, etc. Good show.

The way I see it - it just has to be something in your config. I have never seen or experienced this “failure to charge” issue in notebooks, so I have to conclude it is unique to your build / environment, etc.

Just to be absolutely sure - have you disabled ACPI by any chance? That might muck it up. Also, are you running a stock kernel from the repo or a custom kernel?

Lastly, just as one idea you might want to give this a shot: perhaps it would work for you too.

Also, how about testing with a LiveCD (maybe compare Ubuntu/Kubuntu and Suse) and see how the charging performs in those environments.

Let me know what you find, I am interested in know what the deal is.


sorry for cant help you. waiting for others’ reply. or i will have the same problem