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Re: Power Management

Matthew Garrett wrote:
On Mon, Feb 16, 2009 at 07:02:52PM -0500, brad longo wrote:
As I'm sure most of you know, leaving your laptop plugged in and charging with a full battery charge is harmful for the battery. I have been trying to see if Fedora's power management tool has something built in so that when the battery reaches full charge, it will then discharge to lets say around 95% before beginning to charge again. Friends of mine with the same laptop use such measures except they are running windows. However, based on the fact I did not see any documentation about this, and that my battery charge does not appear to fluctuate at all once it becomes fully charged (according to the statistics), I'm guessing no such thing exists in Fedora. Does anyone have any information as to whether this safety feature exists in Fedora, or whether some other measures exist instead? Basically I'm just wondering if I need to periodically unplug my laptop to preserve the lifespan of the battery, which would be annoying. Also if this is not a feature is anyone working on developing something like this for Fedora?

Charging of the battery is generally under firmware rather than software control. Laptops will typically stop charging at 100%, at which point the battery will slowly self-discharge. When the battery hits some threshold (typically somewhere between 95% and 97%) the firmware will start charging again.

What you're talking about is presumably an interface to modify that threshold. This is device specific. The tp_smapi driver (which is not in the kernel for exceedingly dull reasons) allows this to be configured on Thinkpads. I don't believe that we know how to on any other systems.

Thanks this is the information I was looking for.


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