View Full Version : Powerbook internal battery power

22nd July 2010, 11:59 AM
I have a powerbook that can go to sleep, have its battery removed while connected to no other power and stay in sleep mode for a few minutes until I connect another battery. A pleasant feature I hadn't experienced before.

Is the internal battery that keeps power in sleep mode something like a LiIon that needs to eventually be replaced, or is it a big capacitor, or something else? I'm unfamiliar with just how much charge a capacitor would need, or whether it's practical for such use, but just curious! Since the powerbook is now more than 5 years old, I'm guessing a LiIon wouldn't have survived until now, but the manual calls it an internal backup battery. Manuals have been known to oversimplify, though.

Anyone who's disassembled a 1.67 know which it is?

22nd July 2010, 12:14 PM
Most Powerbooks of this ilk came with a PRAM backup battery (which is Li-ion); 12" Powerbooks and iBooks did not (so if you removed the battery, time/date settings are lost).

I've seen some PRAM batteries last years, and others not at all - they're constantly recharged which I believe is "good" for this type of cell. I believe it requires quite a bit of tearing apart of a Powerbook to replace, however.

Example of battery:

Maintenance / Tools - NewerTech Replacement PRAM/clock battery for PowerBook G4 17" Aluminum 1.67GHz systems - MacFixit Australia - Shop For Apple Macintosh Accessories, Apple Mac Upgrades, MacBook and MacBook Pro Battery, Mac Screen LCD, Phone Cases (http://www.macfixit.com.au/shop/index.php?_a=viewProd&productId=1113)


22nd July 2010, 12:20 PM
Thanks Byrd, I'd been aware of the PRAM battery's importance for date, time, boot volume &c., I just didn't know if it was used to maintain sleep mode for those crucial few minutes while changing the main battery.

Looking through takeaparts doesn't show anything else it could be, which leaves only the PRAM itself. I'm impressed!