Optimizing laptop battery life with AcpiTool and PowerTOP

Calibration

If the rows for design capacity and last full capacity clearly differ, individual cells are more or less exhausted. This can be partially reversed by recalibrating the battery. To do this, drain the battery several times to the final discharge voltage and then fully charge it again.

For proper discharging, adjust the threshold in the energy manager of the desktop environment so that the computer switches off at minimum battery charge level (Figure 3). This ensures a clean shutdown of all processes and applications and minimizes the risk of data loss. Additionally, it avoids an accidental deep discharge, which can damage the battery.

Figure 3: On KDE, adjust the discharge threshold in the Battery Monitor if your hardware supports it.

Charging the battery for two to three hours after each complete discharge completes the recalibration and brings the last full capacity values back up to something approaching the design capacity. This accordingly extends the laptop's battery life.

Switching Off Unneeded Components

Switching off components and services that you do not need for operations helps to extend a laptop's battery life. For example, modern devices often have WiFi modules that you can switch off to save power. Besides a permanently running disk, a bright display is one of the biggest power guzzlers.

Although Linux now offers mature energy-saving options, which you can conveniently adjust through a graphical interface on the desktop, they do not include the full range of sensible energy management capabilities: To locate power-hungry components and services on Linux off the beaten track, you will find Intel's PowerTOP a useful companion.

PowerTOP is found in the repositories of many distributions. If you find two versions of the program, then install the 2.x version: This is the first version to include the code that supports convenient control of individual laptop components. If no packages are available for the distribution you are using, download the PowerTOP source code [5] and build the program by following the how-to.

Next, run the program in a terminal as an administrator by typing the

powertop

command. The tool lists the status of the hardware it finds in an ncurses interface and updates the data in real time. You will see not only the level of utilization for individual components, but also for services (processes). If PowerTOP permanently shows a value of 100 percent for individual subsystems, this means the components do not support power-saving mechanisms.

In the tab bar at the top of the screen, you will find a Tunables option on the right. The matching list details the computer components and specifies whether their current settings save energy or impede energy management (Figure 4). It makes sense to modify the settings for components listed as Bad.

Figure 4: PowerTOP shows that this configuration has a potential for optimization.

To do so, select the device with the arrow keys and press Enter; a dialog for editing the settings is then displayed. PowerTOP automatically determines better settings and implements them when you press Enter again. Pressing R checks to see whether the program has made the changes.

Thanks to the descriptive names in the list, it is easy to identify hardware that you rarely use and thus does not need to be switched on permanently. Because PowerTOP makes the settings permanent, you can genuinely save power thanks to smart changes.

Conclusions

The high level of component integration in current laptops makes it difficult to configure meaningful energy-saving options. AcpiTool and PowerTOP are two useful tools that help keep your battery in good health and achieve the maximum lifetime to boot. Controlling these little helpers is extremely simple, allowing you to identify and disable the power hogs on your system.

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