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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > MacBook waits too long to go to sleep on low battery

MacBook waits too long to go to sleep on low battery
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tooki
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Jan 28, 2009, 07:57 PM
 
Hey folks,

I've got a white MacBook (the entry model from before the unibody came out). 2.1GHz, 4GB RAM, 500GB HD, but this problem existed before I upgraded from the stock 1GB/120GB configuration.

Anyway, you know how when your battery is almost done, you get the little dialog box warning you? And how then, when there's just a hair of power left, the system is supposed to go to sleep, so you don't lose your open work? It's supposed to go to sleep with a small reserve of power to keep the RAM going for a few minutes, and then the Safe Sleep is supposed to protect you if you don't make it to an outlet before the battery totally runs dry.

Well, mine doesn't do that. After the warning dialog, it waits until it has basically NO battery left, then begins the going to sleep process. Since Safe Sleep (the default on MacBooks) takes at least a full minute to sleep the machine, the battery invariably has too little power to get even a fraction of the way through the going to sleep process. (It usually gives out after about 10 seconds.) So instead of Safe Sleep giving me extra protection, it invariably causes my system to go down hard.

I've reset the SMC repeatedly, which is the only advice I've seen. The battery and rest of the system work perfectly, aside from this really annoying problem.

Any ideas?
     
seanc
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Jan 28, 2009, 08:08 PM
 
Well we can try disabling Safe Sleep to see if it sleeps normally when the battery is run down:
sudo pmset -a hibernatemode 0

I don't think safe sleep/sleeping when the battery is low has been reliable for me since I got my first notebooks that supported it. The old iBook always slept fine.
     
Simon
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Jan 29, 2009, 03:36 AM
 
Yep, I disabled safe sleep too. I'm much faster saving critical documents than the system is at writing out 4GB to disk. I don't like the long pause before sleep anyway.

What you're observing is IMHO buggy behavior. I don't know when Apple introduced this (IIRC correctly it started before Leopard) but sometimes MBs don't get proper low-battery warnings or they pop up too late (as in your case). Obviously it could be a bad battery or you need an SMC reset. But I have myself experienced it happen on a MB with a pretty new battery and it persisted even after an SMC reset. I know this is not what you were hoping to hear, but I think this is just a bug and so far there's no obvious work-around.

Just to be on the safe side, how's your battery? Is capacity still good?
     
tooki  (op)
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Jan 29, 2009, 06:11 AM
 
seanc: Yup, I did that already, and "normal" sleep works fine. B

Simon: The system was bought at the end of August, so battery is basically new and has excellent run time, and it's done it since day 1. As I wrote in the post, I've reset the SMC repeatedly with no effect.

As for how long it takes to do Safe Sleep, this problem exists for me with both the current 4GB configuration as well as the original 1GB. Either way, the battery runs out of power long before it's had a chance to get even partway through writing.
     
Spheric Harlot
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Jan 29, 2009, 09:26 AM
 
I had the same problem, and it didn't go away until I got the battery replaced.

Our tech surmised that it may be a single bad cell that's tearing down the battery's real capacity just before empty, while the system thinks it's still got some reserve.
     
   
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