User:Tonyr/Journal/Jun07

15jun07

PRAM (bacup) batteries
The PRAM battery for iMacs and G3/G4 towers is a smallish cylindrical 3.6v (or 3.7v) lithium battery. Some are green-and-white, some are red/silver/yellow, some are blue-and-white, some are purple-and-green. A suggested good battery voltage range is 3.39v to 3.69v. A battery showing a lower voltage is considered 'bad', and should be recycled.

All G3 ibooks and G4 12" ibooks do not have a PRAM battery. They use a capacitor to supply enough power to maintain the clock and PRAM contents for about 20 seconds while changing a system battery. This is documented at http://docs.info.apple.com/article.html?artnum=58445 and http://docs.info.apple.com/article.html?artnum=86181 .