May the batteries be with you.
For information about available battery types, take a look at the Hardware Features chapter above.
Please see the Battery Powered Linux Mini-HOWTO and the TuxMobil battery page for further information. A survey of other means to supply power for mobile computers e.g. solar energy is available at TuxMobil. For general information about batteries see the Battery FAQ.
Stephen Rothwell proposed a patch that will add multiple battery support to the kernel APM.
From the mobile-update page (modified by WH): Discharge the battery. If your battery runs only for about 20 minutes, you probably suffer from memory effects. Most laptops do not discharge the battery properly. With low powered devices like old computer fans they can be discharged completely. This removes memory effects. You should do so even with LiIon batteries, though they don't suffer much from memory effect (the manual of an IBM™ Thinkpad says to cycle the batteries through a full charge/discharge cycle 3 times every few months or so).
Try this at your own risk! Make sure the voltage of the fans is compatible to your battery. It works for me.
In the US, this company has most batteries for anything and can rebuild many that are no longer manufactured: Batteries Plus, 2045 Pleasant Hill Road, Duluth, GA 30096 +1 770 495 1644.
The battery-stats package collects statistics about the (lack of) charge on laptop batteries. It also contains a simple graph utility to show the battery charge over time or detect a misbehaviour of the battery which might announce a coming end of batterylife. Battery-stats knows nothing about electrochemical stuff going on inside batteries - hence it will not try to make any predictions whatsoever. But somebody with knowledge of batteries should be able to tell whether they are behaving OK. This package uses APM; there is no support for ACPI yet.
IBAM (Intelligent BAttery Monitor) is an advanced battery monitor for laptops, which uses statistical and adaptive linear methods to provide accurate estimations of minutes of battery left or of the time needed until full recharge. This package uses APM; there is no support for ACPI yet.
A hacked rclock . Booker C. Bense has hacked the rclock program to include a simple battery power meter on the clock face.
xbatstat . A battery level status checker for Linux and X.
The sbsutils package is a set of utilities programs to handle the Smart Battery on laptops, it offers Linux kernel & ACPI support for the Smart Battery System found in some laptop computers.
These are the most important factors which have influence on the battery uptime. Please see the appropriate chapters for power saving tips:
Getting your computer to use the least amount of power can be problematic. Intel's http://www.linuxpowertop.org/index.php project provides information on reducing power usage, tips, and tricks for Intel-based computers running Linux. As a first step, Intel has released PowerTOP, a tool that helps you find what software is using the most power. By fixing (or closing) these applications or processes, you can immediately see the power savings in the tool. You'll also see the estimated time left for battery power if you are running a laptop. The Tips & Tricks page has fixes for a lot of the issues that are already found.