No low battery warning. Reset PMU?

I attempted to reset the PMU last weekend. Looked up and followed the instructions. My understanding was the clock time would be off if the PMU was successfully reset, but my clock time stayed correct. Any insights on whether I did something wrong?

With ibook shut down, I held down shift/option/command (i think that's right....no on the fn key) while depressing the power button. I waited 5 seconds, then powered up again. I didn't hear anything or notice anything different.

Yep. That's what I did. (Without the instructions right in front of me, I guessed wrong on one of the keys, but I was following the instructions you posted, which I got from the Apple Web site.) And I do have Airport with Safari set to open automatically, so I guess that's why the time didn't change.

I think maybe it's just time for a new battery.

Thanks for your response!

I'm trying to mark as solved and award points.

The option key is NOT the one with the Apple. There should be a key that says "option."

I think one way you might be able to tell if the PMU has been reset is to run a log in System Profiler.

Go to About this Mac under the Apple and then click on More Info. Scroll through to logs. I can't remember which one it was (console maybe). You might have to do this on the day you do the reset. When I read through my log on the day of my attempted reset, I found a list of messages from that day's date, followed by a date of Dec. 31, then followed by more of the current date. (I maybe a log is only generated when you actually go to System Profiler, and then remains there until you delete it??) The Dec. 31 listings had a message that read "WARNING: preposterous time in Real Time Clock--CHECK AND RESET THE DATE." Another listing said: "Clock Reset! PMU WAS PROBABLY RESET SOMEHOW!!"

Might be helpful to some of you out there...

Message was edited by: Diane Wordsmith

Colwn, ahhh, those tricky UK keyboards. Glad you figured that one out.

Well...not sure how much light I can shed, but I'll try.

Calibrating is charging your battery to full and then running it all the way down until the computer actually goes to sleep. (The complete process might actually entail fully charging it again?) Anyway, this complete charge and drain is supposed to calibrate the battery, and, if done on a monthly basis over the life of the battery, should extend its life. (Mine is already 2 years old, so I think I may have waited a bit late.)

Resetting the PMU (Power Management Unit) can help increase battery efficiency, charging, etc., if your PMU has become unstable. Depending on the condition of your battery, it might help, might not.

Not sure if your last question was about the calibrating or resetting the PMU (in reference to whether you'd accomplished it). If your time reset -- and you tried it again holding the correct keys 🙂 -- then I'd say you probably were successful. If you charged your battery all the way up then drained it down, then you calibrated.

I've calibrated and reset the PMU, and I'm still consistently getting about 2 hours from a full charge. (Which compared to some folks ain't bad, but it's about half of what I was getting.) We'll see whether the low battery warning message comes back now that I've reset the PMU. I don't think either of them has affected my battery life/efficiency. I think I'm just about due for a new one. My ioreg command in Terminal gave a cycle count of 319 on my battery; I read somewhere that after 300 you're on the downhill slope.

Don't know if that helps....

Cheers!

I can report that after successfully resetting the PMU, the Low Battery Warning is working again. No real effect on the time I'm getting from the battery, but nice to know the warning is actually working now.