Battery life dropped considerably on Mountain Lion.

so - I have a mac genius appointment booked for tonight and was going to ask them to sort out my computer (as its still under warranty)

Brought it into work and now the battery shows 8hours! 😟 Regardless of the time I get out of the machine - the estimations are all ooooover the place - and I've had a fair few charge cycles and would expect it to be stable!

Same here. Brand new MacBook Pro i7 2.3 Ghz. Thought it was because I've putted in another hard drive but found this discussion. Even in sleep mode it consumes 5-10% of battery life within 12 hours. Weird, and obviously it has something to do with ML.

you tried turning off power nap?

There is no power nap on this machine (non-retina), is there..?

sorry - I thought it was a ML feature - perhaps its retina only

Powernap when on battery is most definitely turned off (but on when plugged into mains).

I might turn that off to test, but I know I get a TM backup when it's plugged in, and don't get one when it's not.

It is a ML feature. But ss far as I know power nap is limited to SSD equipped Mac's.

Nickholl said:

"Brought it into work and now the battery shows 8hours!..."

Going to annoy you here with my longshot question:

Do you plug your Macbook in to a cabled ethernet network when you are at work?

My customer found his battery life was just fine when he reset the SMC then avoided using wireless.

Perhaps your work doesn't have a wireless network set up so you're observing the same thing.

Also curious if any other users here are experiencing their poor battery life after resetting their SMC and using CABLED ethernet only.

No one replied when I asked last time, but the thread has been livelier over Thanksgiving. Anyone willing to check for me?

My time estimate still seems to be wildly unpredictable - the % does seem stable however. What do people think - is the % quite a reliable stat to go by?

Nickholl wrote:

My time estimate still seems to be wildly unpredictable - the % does seem stable however. What do people think - is the % quite a reliable stat to go by?

The only reliable way to see how long your battery will last is to run it until it is flat, everything else is a guess (or estimate if you prefer)

yeah I guess .The % prediction does seem to be a lot more stable than the predicted time though

Nickholl wrote:

yeah I guess .The % prediction does seem to be a lot more stable than the predicted time though

But is it right?

Off course it is right, it is just reading the amperages from your battery. But it might very well be the case that the first 50% drains quicker than the last 50%!

🙂 hard to tell. It does seem to be reassuringly high though 🙂 ie. Ive been using the laptop for a couple of hours and it says 61%. the time estimate goes between being 3.5 and 5 hours. This is a lot better than what I used to get before doing a fresh install. I might try reinstalling from my time machine backup tomorrow and hope nothing changes :-s

crossbytje wrote:

Off course it is right, it is just reading the amperages from your battery. But it might very well be the case that the first 50% drains quicker than the last 50%!

Yes it merely describes how much of the batterys charge has been used, it however tells little about how much time is left. Time left relies on 2 factors, battery charge available, and load on the battery, which changes as you use the computer.

There is only one way to know how long your battery will last and that is to run untl flat. Even then you won't know if it will be the same the next time you do it.