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I recently purchased a laptop with an i7-640m processor (blinded by a discount), and my battery life is fairly horrendous: the manufacturer given battery life is 6 hours (I know, it's an upper bound), and I barely squeeze out 3 hours with light usage+wifi. I can't seem to find any information on whether swapping out the processor for a i5 or even an i3 would significantly extend the battery life, aside from people baldly asserting "it should extend battery life" and my own intuition.

Has anyone tried to quantitatively compare these processor families with respect to battery life?

Note that the upper-bound on the battery life was probably with the default i5 configuration, and that my laptop heats up very quickly and stays hot, possibly pointing to more power dissipation than the laptop was designed to handle. I should also note that Engadget gets around 5.5 hours with a similar usage profile, for a i5 configuration. The TDP is exactly the same for all three (i3-3xxm, i5-5xxm, i7-6xxm)

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Battery life is always overstated by Notebook manufacturers, I always cut them in half for real word numbers. –  Moab Dec 12 '10 at 21:27
    
I doubt it will make much difference given that the TDP is the same. –  David Schwartz Dec 22 '12 at 21:34

3 Answers 3

can't seem to find any information on whether swapping out the processor for a i5 or even an i3 would significantly extend the battery life,

It doubt it would. 3hrs is about average.

. I should also note that Engadget gets around 5.5 hours with a similar usage profile, for a i5 configuration

Different battery capacity, most likely.

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I think 3 hours is even quite a long time ;) Mine won't last for even 2 hours with i5. –  BloodPhilia Dec 11 '10 at 9:39
    
My i5 Sony Vaio has an interesting feature built in that further reduces the battery working time by stopping charging at 80% !! You can disable it but as I mostly work with mains power connected I've left it in "battery care" mode as it supposedly prolongs the life of the battery. –  BrianA Dec 11 '10 at 14:53
    
@BloodPhilia My Envy lasts about 4hr on IGP, it's got an i5. @BrianA IMO that is just marketing speak –  Sathya Dec 12 '10 at 3:04
    
@BloodPhilia, I'm just used to having a longer battery life. –  thenoviceoof Dec 12 '10 at 18:23
    
doesn't seem like engadget was using an extended battery –  thenoviceoof Dec 12 '10 at 18:24
up vote 0 down vote accepted

This forum thread has an interesting summary:

http://forum.notebookreview.com/hp-envy-hdx/501066-envy-14-battery-life-log.html

The envy 14 shipped with i3, i5, and i7. The 6+ hours from the i3/5's seems to be mostly from people that just ran their battery down while doing nothing, but on average it seems that i7 yield a lower battery life by a noticeable amount.

Of course, this is talking about the i7-720m, which has 4 cores. The difference between i5 and i7-640m might not be so noticeable. Hmm.

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Even though I agree with the other posts that mean battery is 3 hours, etc, etc... please notice that battery life is very much affected by: screen brightness, wifi, cdrom, and specially Window's power profile (search "energy options" in the start menu box).

When you have selected the "high efficiency / speed profile", the CPU runs at maximum speed always and thus drains battery. Try to select a lower profile to do your test.

Although my answer is also generic, I think it should be taken into account.

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