Winter 1998: Time to change your Macintosh's battery?

Microcomputers and Workstations

Time to change your Macintosh's battery?

Seth Novogrodsky and Aron Roberts

If your Macintosh is more than a couple of years old and starts exhibiting any of the following symptoms, it may be time to change its battery:

The time and date are no longer correct. Each time that you start your computer, the date is set to some time in either 1956 or 1904. Files that you create or modify reflect the erroneous date.
Your monitor settings may have changed. The screen's resolution or the number of colors it displays may no longer be set to your preferred settings. For instance, even though your monitor may be capable of displaying color, the screen may have reverted to black and white or grayscale.
In some cases, when you turn on your Macintosh, your monitor's screen may be completely black, even though your computer and monitor appear to be on. According to Apple, Macintosh models that can experience this problem as a result of a low battery include the Quadra 605, Performa 475, Performa 476, LC 475, Centris 660AV, Quadra 660AV, Power Macintosh 6100, and the Performa 61XX computers. (There may be other causes for this problem, as well.)
The window accent color and the color of highlighted text have reverted to the system defaults.
The AppleTalk network connection may have been changed from EtherTalk to LocalTalk (if you have the Network control panel), or from Ethernet to Printer Port (if you have the AppleTalk control panel). This could prevent you from accessing file servers or from printing to your usual printers.
You may be unable to print or see garbage characters at the start of your printouts. (Of course, there are many other possible causes for printing problems like these.)

If the battery in your Macintosh is low or dead, your Macintosh will "forget" changes you make to these settings in various control panels and the Chooser once you turn the machine off. All of these settings are stored in "PRAM." The next time that you turn your computer on, these problems will reoccur.

What is the PRAM?

All Macintoshes, including desktop models and PowerBooks, have a small amount of nonvolatile memory called "parameter RAM" or PRAM. A lithium or alkaline battery keeps the contents of the PRAM intact, even when your computer is turned off. (In PowerBooks, these batteries are different from the larger removable battery packs that keep your PowerBook operating when you're on the go.)

Many system preferences, such as the date and time, monitor settings, cursor blink rate and keyboard repeat rate, startup disk choice, and text highlight color, are stored in PRAM. If the battery in your Macintosh expires, the information stored in PRAM will become lost and your Macintosh may exhibit unusual behavior.

Is it time to change your battery?

The battery that keeps your PRAM alive typically lasts from three to five years. If your Macintosh is that old, and you are experiencing these problems, there is a good chance that your battery might be dead or have lost much of its capacity.

However, sometimes the contents of the Macintosh's PRAM can become lost or corrupted for reasons other than a battery failure. In these cases, resetting the PRAM to the Macintosh's defaults, called "zapping the PRAM," will correct these problems. You should try this before having your battery changed.

To zap the PRAM, press and hold down Command-Option-P-R (all four keys) when starting or restarting your Macintosh. After you have heard the startup chime several times in succession, you can release these keys.

After zapping the PRAM or having your battery changed, a number of your Macintosh's settings will have reverted to their factory defaults. You might then need to reset a number of your preferences manually. You can do this by going into a number of control panels and the Chooser and resetting your desired preferences.

The specific control panels that you may need to open may vary depending on the system software that you are running. These may include the Memory, Brightness, General Controls, Date & Time, Keyboard, Mouse, Color, Monitors, Sound & Displays, Monitors & Sound, Startup Disk, and Appearance control panels. Most of the settings used by these control panels are stored in PRAM.

Should you change the battery yourself or have someone else do it?

Apple recommends that batteries that retain the contents of PRAM be installed by Apple-authorized technicians. In any case, you probably should not change the battery yourself if

Your machine is under warranty or AppleCare.
You are not comfortable opening up your computer case.
The battery is soldered onto the motherboard.
Your machine is a PowerBook (the batteries that keep your PRAM intact are not designed to be user-accessible).

In general, if you have any doubts about changing the battery yourself, you probably should let someone else do it. It is possible to damage your computer if something goes wrong.

You can have the battery changed at any Apple-authorized service center, including the Workstation Hardware Support Group (http://www-whsg.berkeley.edu/, 50 University Hall, caltec@socrates.berkeley.edu, 643-6937). Macintosh specialty stores that provide repair and upgrade services such as MAC, 2010 Shattuck Avenue, Berkeley, can also change the battery.

If you change the battery yourself, it is important for you to have a diagram or photo of the logic board or otherwise some idea where the battery is located. You should also wear a grounding strap and unplug the computer. The battery in many Macintosh models is mounted in a rectangular plastic housing. You will need to remove the old battery carefully from the housing, and replace it with the exact same type of battery in the same orientation. (You may need to remove the top of the housing first.)

In some Macintosh models, the battery may be located near RAM (SIMM or DIMM) sockets. It is important not to inadvertently unseat the SIMMs or DIMMs or leave other cables or system components disconnected when replacing the battery.

Apple offers a Tech Info Library article "Macintosh Family: Batteries & Part Numbers" (Article ID 11751) that describes which batteries are used in various Macintosh models along with Apple's own service part numbers. (Apple does not sell these batteries directly to end users.) In addition, there are several informal sites on the Internet that provide information on the topic of Macintosh batteries. Newer Technology provides information about which batteries are used in different Macintosh models within their freeware utility Guru (Guide to RAM Upgrades), downloadable from http://www.newertech.com/software.html.

However, it may be easiest just to take your old battery with you when purchasing a new battery. Stores in the Berkeley area which sell batteries that work in Macintoshes include Ace Berkeley Hardware, Al Lasher's Electronics, Radio Shack, and MAC (all of which can be found in the telephone directory).

After your battery has been changed, be sure to change the settings in the control panels as described in the section Is it time to change your battery? above.

Berkeley Computing & Communications, Volume 8, Number 1 (Winter 1998)
Copyright 1998, The Regents of the University of California