The iBooks carry a 50 or 61 watt hour battery (12" has the 50) while the Powerbooks only have a 47/46/58 watt hour battery (listed going 12"/15"/17").
Also, the Powerbooks tend to have more in them to have running (eg. more power hungry vid cards) so that is another factor as to why they have a lower battery life. Although with the latest battery update the times are getting closer to the 4.5 hour battery life promised.
There's another factor, too. Most iBooks (except the newest ones) sport a G3, whereas the PBs use G4s which draw a bit more juice to run and cool.
My three favourite battery-savings tips:
- disable Airport until you need to get your email or check the web;
- drop your screen brightness way down to the second-to-last notch;
- don't run antivirus or software updates when you're unplugged.
The upgrade to 10.2.8 put a serious dent in my PowerBook 667s battery life. (The second version of the upgrade - I thought I waited until it was safe.)
I was really hoping that the battery update released yesterday would fix whatever was changed, but it won't install on my computer.
"This software is not necessarily for your computer." WTF?
Was there a firmware change in the batteries in 10.2.8?
I've read that Apple is replacing batteries for people in this situation, but for once I didn't order Applecare with the PowerBook. And then they promptly bumped the price up to over $500. so didn't add it before the year ended.