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On my laptop, I'm currently running Ubuntu 12.04 Beta 2, which works great. But sometimes I just want to lie in the couch watching a movie or reading an e-book. At times like that, the power consumption of a modern desktop is a bit of a pain in the bum (about one and a half hour on a full battery).

I know a tablet or an e-book reader would be probably the perfect solution for this, but they usually cost (rather a lot) of money.

Is there a simple environment I can install (or run from USB/CD, don't care much) which doesn't use so much power, and allows me to simply read an e-book and (optionally) watch a movie? I don't need any fancy effects and features or anything, I just want a long battery life.

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The problem is that even when your OS is using all available power saving modes of your hardware (Ubuntu is not too bad at that), the minimum power consumption for laptops is still quite high.

Tablet and phone chipsets are specifically designed to avoid leaking currents; laptop CPUs and chipsets are not (yet) that energy efficient.

Even if you aren't actively using your computer, the hard disk drive is still spinning, the graphics card is still redrawing the screen 60 times a second from data coming from the RAM, the RAM itself has to be refreshed so your data is ot lost...

A tablet has no hard disk to begin with, and the mobile RAM in it is specifically designed for low idle power usage. Mobile CPUs also can throttle down to much lower speeds than desktop CPUs.

You might be able to squeeze some additional minutes out of your battery by reducing the backlight, using the newest OS and drivers available and enabling all energy saving options, but don't expect any wonders - there are literally orders of magnitude between the idle power usage of an embedded CPU (for tablets and smartphones) and that of a regular laptop system with a lot more, and more powerful, components.

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E-book readers are relatively inexpensive. Check prices for basic Kobo ($67?), basic Kindle and similar devices. As you know, the battery on these can last weeks or even months of typical usage.

Decompressing and playing video is inherently a power-consuming activity.

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Yeah, I know about the Kobo and Kindle. But for a small device you can do nothing on appart from reading e-books, around 70 euros still seems rather expensive to me, as they sell cell phones for as low as 15 euros these days. AndI've already got my laptop. The only problem is the short battery life; which is why I'm asking for a solution here. –  RobinJ Apr 10 '12 at 13:55
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The advantage of e-book readers is the e-ink screens, as they are excellent for reading on. You will thank yourself in 10 years when you don't have to spend thousands on corrective eye surgery because you broke your eyes reading on a shining rectangle. –  kotekzot Apr 10 '12 at 14:46
    
@kotekzot: great point! –  lupincho Apr 10 '12 at 14:57
    
@kotekzot I've been reading on a shiny rectangle since I was 4 :p –  RobinJ Apr 10 '12 at 16:50

The minimum a laptop needs is an OS. The best you can do is find every setting in that OS that has to do with power management, and set it to the most economic option. Modern BIOSes have options for power management too. CPU's often have a setting that lowers the clock speed when it is under no or low load. If you'd like to turn your old laptop in a dedicated long-lasting movie and reading machine, you can downclock everything.

If you don't need wifi, turn it off. Lastly, not only good for your eyes when reading or watching movies is to lower the screen backlighting. Nearly every laptop, if not every, has a button or function key to do this easily.

Basically those are all the steps you can take to reduce power consumption, but I'm afraid that on most laptops you can't get more than two and a half hours at best.

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Well, I know you need an OS. That's why I'm asking if there's an OS with a long battery life. But I'm afraid things like powertop, turning the screen brightness down, and speedstep don't really make much of a difference when it comes to battery life. –  RobinJ Apr 10 '12 at 14:00
    
Screen brightness definitely makes a difference. At least 10 minutes on my machine between minimum and maximum. –  MDeSchaepmeester Apr 10 '12 at 14:02
    
Yeah, I know it makes a bit difference. But I was more targetting at a big change, like a one hour change :p –  RobinJ Apr 10 '12 at 14:06
    
I understand that, but the fact that any system requires at least an OS, a solution is going to be very hard to find. And, if speedstepping/downclocking don't make much difference, I don't think it's technically possible to develop one that makes for such extreme change in how long your battery lasts. –  MDeSchaepmeester Apr 10 '12 at 14:36

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