Battery Life - resetting SMC will sometimes increase it by 3 hours!

Question

Level 1

19 points

Battery Life - resetting SMC will sometimes increase it by 3 hours!

I've searched the forums for someone else reporting this strange behavior but couldn't find anything. Upon charging, my MBA consistently gives me 2 hours of battery life. However, I have gotten it to jump to 5 and even 6 hours of battery life by resetting its SMC. However, it's not every time - actually, I've only been able to do it maybe 3 times out 25. I've gotten the battery replaced and I've experienced the exact same behavior with the new battery.

Does anyone have any idea why, every once in awhile, resetting the SMC increases my battery life and why it doesn't "stick"? It's very frustrating to get only 2 hours of battery life (yes, with all of the power-saving features turned on or enabled - such as screen brightness, WiFi, Bluetooth, etc.).

Thinking I had a faulty battery, I thought for sure the new one would solve the issue. Unfortunately, after calibrating the battery (again) yesterday and charging it all night - I, once again, only have 2 hours of battery life.

What's really frustrating is that I've seen and experienced the 5 and 6 hour battery life a few times so I don't think it's the battery. It must be something else (software, firmware (yes, I've done the SMC Update), hardware?).

Anyone have any ideas or tips I can try?

Thanks,
Steve

Posted on Oct 30, 2008 8:36 AM

Reply

Answer 1

Oct 30, 2008 9:51 AM in response to mnsaint

Are you sure? Are you measuring actual runtime or the estimated time remaining? Because if you are relying on the estimates resetting the power manager may throw those off for a while and give you false high readings.

Reply

Answer 2

mnsaint Author

Level 1

19 points

Oct 30, 2008 3:20 PM in response to Edmund Pirali

Actual running time.

When, on that rare occasion, resetting the SMC pushed the time remaining up, I was skeptical so I ran my MBA until it died. It was close to five hours.

That's the frustrating thing - there's no consistency to it. Most of the time, I only get 2 hours. However, if I reset the SMC, I just might get more. Though, like I said earlier, it's not very often.

Thanks for your reply,
Steve

Reply

Answer 3

Lun324

Level 1

0 points

Nov 5, 2008 12:24 PM in response to mnsaint

Hi,

I have also come across the same problem with my new Mac Book Air! The first couple of months it would last about 4-5 hours, but lately even with everything turned off (like bluetooth, and having the dim lights, etc..) that should take up a lot of power, it only lasts at the most about two hours!! VERY DISAPPOINTING! I went to the Genius store to try to get this looked at, thinking I might have a defective battery but the guy basically told me that he didn't see anything and nothing was offered, so I don't know what to do now...All I can say that after having it only a couple of months, a problem like this should not be happening, or it should be something that should be fixed!

Reply

Answer 4

mnsaint Author

Level 1

19 points

Nov 5, 2008 2:58 PM in response to Lun324

Have you tried resetting the SMC?

1. If the MacBook Air is on, turn it off.
2. Connect the power adaptor to a working power source.
3. On the MacBook Air keyboard, press (left) Shift-Control-Option along with the power button once. Note: You must use the keys on the left side of the MacBook Air keyboard.
4. Wait 5 seconds and press the power button to start the MacBook Air.

Every once in a great while, it actually allows me five hours of battery life. Most of the times, it doesn't make a difference. That's the weird thing. I keep trying slightly different variations of the steps thinking I must be doing something differently the one time it actually increases my battery life. I still haven't figured out that magical combination.

- s

Reply

Answer 5

mnsaint Author

Level 1

19 points

Nov 24, 2008 8:16 PM in response to mnsaint

Update: After finding the dmnotifyd process hogging up all of my CPU and killing it (apparently related to using PAC files in the Network Proxy settings), my MBA's battery life is now consistently 4 to 5 hours per charge.

I guess resetting the SMC must have stopped the process the few times it was successful so it got me looking in the wrong direction. I'm happy to say that killing that process also reduced the heat and fan use by my MBA too.

Just posting this information in case anyone else is seeing less than normal battery life on their MBA. If you are, run Activity Monitor and watch for any processes taking up huge amounts of CPU usage.

Reply

Answer 6

Ewen

Level 6

11,805 points

Nov 25, 2008 5:50 AM in response to mnsaint

Steve St._Marie wrote:
I have gotten it to jump to 5 and even 6 hours of battery life by resetting its SMC. However, it's not every time - actually, I've only been able to do it maybe 3 times out 25.

On apple laptops the smc can eventually become a little screwed-up with time, and this is why resetting it can improve battery life as it resolves power management issues for the notebook. That said, if you're only getting a noticeable improvement about 10% of the time on reset I'd forget about it, reseting the smc has never been a routine maintainance task, and the gains are quite small, 5 hrs is about the ballpark for MB Air life (though it will vary depending on how the machine is set and tasks run on it).

Reply

Answer 7

Jane Knox

Level 3

691 points

Nov 24, 2008 8:38 PM in response to mnsaint

I think dmnotifyd is part of the MobileMe Sync process.

If you try turning off Automatic Sync in MobileMe, you might get the same result?

Reply