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All About the PRAM Battery

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If your computer does not retain parameter RAM (PRAM) settings when it is turned off, this generally indicates that the battery needs to be replaced. If your computer won't startup at all (no power), it might also be an indication that your battery needs to be replaced.
The Cube (and most modern Macs) takes a 3.6V Lithium battery (about half the physical size of a AA battery).

These can be purchased from your local Radio Shack or computer store. They cost about $10. The Radio Shack P/N is 23-026. It's a 1/2 AA cell, purple and black in color. The Apple part # is 922-4028. The battery does not have to be purchased from Apple. It's a pretty standard item, not Cube-specific. It's a 2 minute procedure to change the battery and it's incredibly simple to do yourself. Most reputable AASP's will NOT charge you to install it for you, if you buy the battery from them, because it's so simple. Tekserve, in NYC, for example, will install it for you free of charge. They charge $12 for the battery. If you really don't want to do it yourself - or you want your battery tested before you buy a new one, and you are in NYC... bring it to Tekserve (they have a battery tester and will gladly test your battery for free).  Yes, I used to work at Tekserve. Just because I don't work there anymore, doesn't mean I don't still think they are the best :) If you are anywhere else in the world, bring your Cube to your local AASP or Apple Store.

Instructions for replacing it can be found here:

Macintosh Family: Batteries and Part Numbers, Part 2This document provides information and part numbers for backup and system batteries used in portable and desktop Macintosh computers since Nov 1997. Some Macintosh computers have a backup battery to maintain system settings, such as the date and time, when the computer is turned off . The battery may last up to five years. However, this varies due to the battery's shelf life, and usage patterns of the computer. The batteries used in Macintosh computers are lithium or alkaline, and are commonly 3.6 V to 4.5 V. If your computer does not retain parameter RAM (PRAM) settings when it is turned off (or doesn't turn on at all), this may indicate that the battery needs to be changed. Some Macintosh models may display a black screen (no video) when you turn them on if the battery needs to be changed. If you are uncomfortable changing the battery, an Apple Authorized Service Provider can install one for you.

PRAM stores certain system and device settings in a location that Mac OS X can access quickly. Exactly which settings are stored in the computer's PRAM varies depending on the type of computer as well as the types of devices and drives connected to the computer.

Some information stored in PRAM includes:
  • Time zone setting
  • Startup volume choice
  • Speaker volume
  • Recent kernel panic information, if any
  • DVD region setting

    Note: Mac OS X stores your preselected DVD region choice in PRAM for easy access. Resetting PRAM does not allow you to change the DVD region.

Unlike prior versions of the Mac OS, Mac OS X does not store display or network settings in PRAM. If you experience a video or network issue, resetting PRAM will not help.

If PRAM is reset, you may need to verify your time zone, startup volume, and volume settings using System Preferences. Certain firmware updates may reset PRAM as a normal part of their installation process.
Resetting PRAM and NVRAM on iMac, iBook, and Power Mac computers:
    1. Shut down the computer.
    2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
    3. Press the power button to turn the computer on. You will hear the computer's startup sound.
    4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
    5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
    6. Release the keys.

Your computer's PRAM and the NVRAM are reset to the default values. The clock settings were not changed.

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