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Increase battery run time on laptops with SSDs Laptop Macs
If you have a Macbook Air with a solid-state drive, you can increase battery life by forcing your machine to always hibernate, rather than sleeping.

Generally, Macs only hibernate (storing the existing system state to disk and powering off) when the battery has gone to nearly absolute zero. At all other times, they sleep -- meaning that the existing system state is stored in RAM, and the machine goes into a low-power mode. The reason for this is that it takes longer to restart/restore from hibernation state. But having the machine fully off does save battery life.

Since the MacBook Air's solid state drive (if you have a model so equipped) has exceptionally fast startup times from disk, hibernation restores are very quick (five or so seconds, in my experience). Also, hibernating all the time will save you battery life -- again, in my experience, up to ten percent longer run times. YMMV.

Numerous utilities are available to change the default low-battery mode to hibernate. I like Jinx's Smart Sleep, which installs as a pref pane and is Snow Leopard compatible.

Remember, if you're hibernating, you use the power button to "wake up," rather than just hitting a key on the keyboard.

[robg adds: You can use this tip on any machine with an SSD, if you're willing to put up with slightly longer "wake" times.]
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Increase battery run time on laptops with SSDs
Authored by: danpritts on Apr 07, '10 07:21:28AM

Since this causes RAM contents to be written to your SSD, it will wear out your SSD faster - remember that SSDs have a limited number of writes.

I don't really know how much faster this will kill your SSD; in practice, maybe not enough to care about. However, I've been avoiding it for this reason.

Note that this hint works fine if you have a spinning disk, too, although with a typical 5400rpm laptop disk it'll take more like 10-15 seconds to wake up.



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Increase battery run time on laptops with SSDs
Authored by: bobthfd on Apr 09, '10 09:20:36AM

I'm actually in the other camp, the one that holds when using an SSD as your boot drive you should disable hibernate and only use sleep. While there may be some savings in battery life I think that this is offset by the amount of SSD drive space that will be consumed by writing memory to the SSD. I have 8GB in my MBP and at $3 - $4 per GB I do not want to dedicate that much space on my SSD to possibly getting a bit more battery life.



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Increase battery run time on laptops with SSDs
Authored by: byrno on Apr 15, '10 11:38:01PM

I had the same idea, and bought an Intel SSD. I have a late-2008 MBP, 4GB RAM, formerly with Apple's 320GB HD, probably 5400 rpm. I timed cold starts and unhibernates (wake up from hibernation) with the HD and with the Intel X25-M 160GB SSD I installed:

Apple's 320GB HD:
Cold start: 49 seconds
Unhibernate: 68 seconds

Intel X25-M 160 GB SSD:
Cold start: 67 seconds
Unhibernate: 83 seconds.

These were my results immediately after swapping disks using Carbon Copy Cloner, so the systems were identical. This doesn't seem to make sense! Launching applications (Word, Safari, iTunes) is faster now - that could be from the fast random read speed of the X25. But my numbers don't match the "5 seconds or so" for wake-up that soulbarn reported (and other reviewers have made similar comments). Repairing permissions made unhibernate a bit faster, but wake-ups aren't much faster anymore, and permissions aren't broken). I installed the early-2010 Intel firmware upgrade; no difference.

Hibernate times now are about 26 secs; unhibernates are generally 45-65 secs since I fixed permissions. I don't remember what choices I had or made when I first mounted the SSD as an external drive to clone my hard drive to; maybe I missed an important option. Neither Apple's Disk Tool nor TechTool Deluxe reports any problem. Usually during unhibernation the indicator with 20 or so little vertical ovals just races along for 5, or 7, or 16 ovals, and then hesitates for a long time before resuming.

Why isn't my SSD faster?



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