[nickw311]

I have noticed recently that my MacBook has been just turning off instead of giving a low battery warning and then going into sleep recently when the battery is low.

Just yesterday I was using the computer from battery, I noticed that it was low, but not in the red area yet. In order to get it to last the rest of my class I turned the screen brightness down and turned off airport. I then checked to see how much time was left and it said 35 minutes. About 5 minutes later it did a hard shutdown, no warning, and the battery indicator wasn't even red.

Has anyone else had this issue? My battery has had 360 cycles so I know it has been used a lot, but it would be nice if it at least warned me a few minutes before it died.

[frdmfghtr]

Wow, that's a lot of cycles. How long has it been since you last did a calibration?

I think that battery capacity is a crapshoot at best, depending wildly on your usage habits. you sound like you drain down pretty far on a regular basis, but without a periodic calibration cycle, accuracy is lost over time and cycles.

[nickw311]

Yeah i haven't really done an actual calibration but I do try to drain it down to the red before charging it.

[ibook_steve]

Originally Posted by nickw311 

Yeah i haven't really done an actual calibration but I do try to drain it down to the red before charging it.

Do you mean that you normally run without AC connected even when you have it available, and then charge it all the way back up all the time? No wonder you have that many cycles. If you have AC available, just leave it plugged in.

Steve

[turnedge762]

I've had that same exact issue. I took it into Apple, and it turned out to just be a bad battery. They replaced the battery under warranty, and I've never had the problem since.

[nickw311]

ibook_steve:
No, when there is power available I always plug it in. But when I begin a discharge because of the lack of power, I usually try to discharge it completely.

I have so many charge cycles because I use my computer a LOT.

[frdmfghtr]

Originally Posted by nickw311 

Yeah i haven't really done an actual calibration but I do try to drain it down to the red before charging it.

Running it into the red generally isn't enough, although I've seen my capacity update periodically when running close to empty.

There's a specific procedure to use when calibrating the battery; you run until the computer goes to sleep on tis own, then let it sleep for about five hours, then recharge it completely.

Calibrating your computer's battery for best performance

Come to think of it, I haven't done one in a log time either.

[Christopera]

I have 133 cycles on a 4 month old MB. I don't see that slowing down anytime soon either.

[analogika]

I *do* get the warning, but then the 'book (November '06 model 2 GHz BlackBook) goes into safe sleep mode, but doesn't make it and just shuts down, hard, in the middle of caching the sleep image.

It's been doing this for a while now, all battery and firmware updates have been applied, and PMU reset numerous times.

I'll test it with a different battery, next.

[Dork.]

If you're seeing a laptop battery run out of juice suddenly after the timer says it still has some time left to go, and you've done all the normal things to try and troubleshoot it (like resetting the Power Manager), then it's likely that one of the cells in the battery is starting to go bad.

The battery cells are usually wired in series to get to the proper voltage. Individual cells can fail such that they drop their voltage before the other, more healthy cells. Since the voltage is determined by all the cells in series, if one fails before the others you'll get close to the voltage threshold and the PM will trigger an early shutdown (the computer bases its estimate on the amount of charge it estimates is left in the battery as a whole, and doesn't know if a particular cell is about to fail). If this failure is fast enough, it will shut down hard before the safe sleep mode can happen.

The OP didn't say how old his battery was, but 360 cycles is a lot. That battery has done its share, perhaps it's time for a new one. Or, there are places that will open up the battery and replace the cells for you. They might even replace them with higher capacity cells if they are available. I've never used them, but there's no reason why that shouldn't work, and IIRC the service is 60-75% of the cost of a new stock Apple battery.

[nickw311]

The battery is about 16 months old, currently working on my 361st cycle ;-)

[nickw311]

I have not reset the Power Management Unit yet, thanks for the suggestion.

Here are the instructions for those who may not know how to do it:
Resetting MacBook and MacBook Pro System Management Controller (SMC)

[Dork.]

Apple has some good pages on batteries now. I'm not sure how long they've been there, they might have been put up in response to people's questions about the iPhone battery:

Apple - Batteries

Apple - Batteries - Notebooks

One page has this nugget of information:

A properly maintained Apple notebook battery is designed to retain up to 80% of its original capacity at 300 full charge and discharge cycles. You may choose to replace your battery when it no longer holds sufficient charge to meet your needs

[Peter]

Yep.
So, OS X can't tell when the battery has lost some of its original charge. So, it may only have 80% of the original charge (in the battery) but OS X doesn't know!
This means when your battery is at 20% (according to OS X) your battery is actually ran out.
So OS X just switches off, rather than giving the alert.

[frdmfghtr]

Originally Posted by Peter 

Yep.
So, OS X can't tell when the battery has lost some of its original charge. So, it may only have 80% of the original charge (in the battery) but OS X doesn't know!
This means when your battery is at 20% (according to OS X) your battery is actually ran out.
So OS X just switches off, rather than giving the alert.

Of course it knows when it has lost capacity--that's what the calibration cycles is for. From "About this Mac"...

Battery Information:

Model Information:
Manufacturer: DP
Device name: ASMB013
Pack Lot Code: 0001
PCB Lot Code: 0000
Firmware Version: 0102
Hardware Revision: 0300
Cell Revision: 0100
Charge Information:
Charge remaining (mAh): 5234
Fully charged: Yes
Charging: No
Full charge capacity (mAh): 5282
Health Information:
Cycle count: 133
Battery health: Good
Battery Installed: Yes
Amperage (mA): -1271
Voltage (mV): 12452

And I don't think it os OS X just switching off; not self-respecting OS is simply going to dump itself hard like that. I believe it is the battery itself that cuts off power to protect the cells from permanent damage.

[Dork.]

Originally Posted by Peter 

Yep.
So, OS X can't tell when the battery has lost some of its original charge. So, it may only have 80% of the original charge (in the battery) but OS X doesn't know!
This means when your battery is at 20% (according to OS X) your battery is actually ran out.
So OS X just switches off, rather than giving the alert.

Remember, the battery is composed of multiple cells (for older Mac laptops, lithium-ion. For newer ones, lithium polymer.)

The real issue is that if one of the cells starts to get wonky, the behavior of the whole battery is wonky. And since there's roughly a 50% chance that any given battery cell is below average (which I hope is obvious), if there are 4 cells in a battery pack there's a 93% chance that at least one of them will be below average. (That statistic isn't entirely made up, although it's been a while since my sophomore Statistics class in college).

under normal circumstances, OS X does a pretty good job at battery management, but if the battery is wonky, all bets are off.