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iBook battery time (tips and info)
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elwood73
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Joined: 07 Jun 2004
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PostPosted: Mon Jan 24, 2005 9:37 pm    Post subject: iBook battery time (tips and info) Reply with quote

The iBook was touted as having a 6 hour battery life. I know tis is probably based on maximum powersave settings, yada yada... but still. When I fire up my ibook on a full charge, with screen brightness at ~12 and cpu running at half speed (600mhz) my apm monitor reports about 3 and a half hours of battery life. A pmu scpecific monitor reports the same. Is this about right?

Also, what tips does the community have on extending this?
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zenlunatic
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Joined: 09 Apr 2003
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PostPosted: Mon Jan 24, 2005 10:46 pm    Post subject: Reply with quote

Yeah 3.5 is about right. Eventually the battery will just die and you really can't do anything about that (not die but not hold the same charge). Turning down the brightness and turning off airport has never seemed to make a difference here. I would say purchase another battery if you need battery life that badly. I'm on my second battery and plan to buy a third sometime soon just to have. However I bought a kensington ac adapter for my ibook because the old ac adapter broke and this adapter supports airplane power plugs and car plugs at only $30 more.

Last edited by zenlunatic on Fri Jan 28, 2005 5:16 pm; edited 1 time in total
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ozonator
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Joined: 11 Jun 2003
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PostPosted: Fri Jan 28, 2005 3:23 pm    Post subject: Reply with quote

In my case (iBook G3, 800 MHz, 12" -- not as new as yours likely are, but not hugely different), I generally assume I'll get at least 3.5 hours out of a full charge. If I need more, though, I generally can get it, though it means being careful about how I'm using the machine -- I can easily get 4-4.5 hours out of a charge when doing that, and have been able to approach 5 hours; using OS X (more on that in a sec), I've even gotten a little over 5 hours a couple of times (what Apple claimed is the maximum battery life of my machine), but as with Linux, that required careful usage.

Turning the brightness down does make a big difference on my machine; it's not always practical in a bright environment, but using very low brightness can add around 30 minutes (rough estimate, that's how it seems to me) to how much I can get out of a charge on my iBook. On the other hand, like zenlunatic, I found that airport usage doesn't make a difference.

Besides brightness, it's just general system load that seems to make a noticeable difference: compiling, watching video, or doing other things that cause a lot of disk and CPU usage just uses more power. Using something to step down the CPU speed a bit when the machine is idle (e.g., cpudyn), or just keeping the CPU speed pegged to a lower speed, helps a little bit, but I've never found that doing that makes a huge difference to battery life.

Re. my comment about OS X above: I've found that OS X seems a little bit better at regulating CPU power consumption than Linux + cpudyn or even Linux with the CPU speed set at half of what it's rated, at least when the CPU speed is set to 'automatic' in OS X. This seems to be supported by the results of the recent performance comparison on Macintouch, which shows a significant speed difference between 'automatic' and 'high' speed settings on a single machine.

What my advice would come down to, then, is that if you need more than 3.5 hours or so reliably and regularly, a second battery is a good idea. On the other hand, if you need it only occasionally for 'light' use like text editing, doing things like turning down brightness, letting the disk spin down, etc., can let you squeeze more out of the battery. YMMV. :)
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