Has anyone ever heard of this problem before? I challenge you!

Question

So guys, recent macbook pro that I purchased - 15inch - intel core 2 duo 2.4 ghz. It's been great. Recently, I had noticed that when the computer was running off the battery - the time indicator for the battery life kept changing drastically like 2:30 to 4:40 etc.
I went and sought the advice of a mac genius at the local apple store. They found that some kernel issue, something software related, was spiking in the activity monitor thereby causing the battery to have to re-evaluate how much time is left rapidly. they said there was nothing wrong with my battery and that I should do an archive and install and see what happens. they also told me they had NEVER heard of this before - which seems impossible - someone has to have experienced this.
anyways, did the archive and install and when that was completed and my computer was 10.4.9 the problem was fixed! time was back to normal.
then mindlessly, i went through the required software updates to get me up to speed and then tried the battery again just to make sure if was working - and suddenly it was back to old problem again. So it must be some apple software update that I downloaded? And if it is, somebody must have heard of this before.
Any help would be much appreciated!
Thank you,
Jack

Answer 1

As I understand it--and this is surely what Retired Engineer was alluding to--your Mac looks at the current battery drainage, combines that with the amount of power in the battery (x%) and computes how much battery time is left. This is why, for example, when you first unplug the computer, the display says "computing" instead of "x:xx time left". But how much power your Mac uses depends on what you are doing. For example, if you let the computer sit, it uses almost no power, and so the computer will show several hours remaining. However, if you then decide to use Disk Utility to "verify disk" or "repair permissions" or something, then suddenly the computer will start spinning and reading the disk, which is rather power intensive, and also it will have to do some computing, which is also power intensive. So display of the amount of time left will drop massively, accordingly, because your Mac battery won't last nearly as long with this amount of usage. But once Disk Utility is done, and the computer is doing nothing again, then your computer will recompute the amount of battery left back to a higher time. And so on.
As a general rule, the more apps you have running, the more disk activity your are doing, and the more services you have on (e.g. wireless) the less battery time you will have.
Rosetta translates on-the-fly programs written for PPC processors, used on older Macs, to something that can run on an Intel Mac like the Macbook Pro. This is computationally intensive and so will slow things down. If you look at Apple > About this Mac > More Details > Software you will see what of your applications are Intel or Universal, and therefore running natively (not Rosetta) or PPC (Rosetta). This information may also appear in Activity Monitor. And make sure you have set activity monitor to show all processes, not just yours.