How can the battery affect how my Mac runs? - Well, when your backup battery is in good condition your Mac will run smoothly, but when it dies... Lets just say it can be cery frustrating at times. When the backup battery can no longer provide enough power to the clock and PRAM when your computer is off the info in your PRAM is lost. The info stored in the PRAM are, as explained earlier, things such as double-click speed, whether AppleTalk is on or not, etc., and when this data is lost, your Mac may start to act as if it is randomly causing problems. In the case of AppleTalk, because AppleTalk is preset to be on and to use the printer port for networking, if you have AppleTalk turned off and a printer attatched to the printer port, when your Mac checks the PRAM it will find that AppleTalk is on and so it will not allow you to print (because AppleTalk has taken over the printer port). That was just an example, but it is a good example of how, when the PRAM data is lost, your Mac can cause more problems that you would expect and you may not know the cause.

What are the symptoms of a dead backup battery? - Here's a list of some of the easiest symptoms to recognize:

• The date and time is reset to an odd time and year whenever your Mac is shutdown
• Many Macs won't start up at all with a dead battery, including the following:
  • Mac II
  • PowerMac 6100
  • Centris 640AV
  • Performa 5500
  • and many more
• The graphics hardware in some Macs in the LC, Performa, and Quadra lines will fail to work correctly (the computer will work fine, but won't display anything) ^NEW
• AppleTalk is turned on (when it was off) whenever your Mac is shutdown
• The selected AppleTalk port (LocalTalk, EtherTalk, etc) has been changed
• Your default printer no longer prints (it gives you an error saying the port is already in use)
• Your Mac boots from the wrong startup disk when turned on
• Your Mac's disk cache speed has been changed
• Your Mac's double-click speed has been changed
• Your Mac's Mouse speed has been changed
• Your Mac's key repeat rate and delay have been changed
• And many more...

If you have more that you would like to add to this list, please e-mail me.

How do I replace the backup battery in my Classic Mac? - Good question, my suggestion, if you don't want to open up your computer or if you have a PowerBook, is to take your Mac to an Authorized Apple Dealer, but otherwise all you need to do is the following:

1. Find out what battery your Mac needs (a list is provided below)
2. Open the case (if you have a compact Mac, like a Mac Plus, you will probably only need to open the battery compartment)
3. Find the battery
4. Remove it (note exactly how it was placed and connected)
5. Place the new batter in exactly the same manner as you found the one you are replacing

Note: some early Mac II's batteries are soldered onto the motherboard, if you are handly with a soldering iron, you might want to risk damaging you motherboard (and causing the batteries to explode due to being over heated) then you can replace them yourself, but if you have any doubts, I would suggest you take it to an Authorized Apple Dealer, or atleast to somebody who you are sure can replace the batteries for you.

What type of backup battery does my Classic Mac need? - Here's the list of part numbers for batteries for Desktop and PowerBooks (includes Mac Portable):

* Logic boards of the Color Classic, Macintosh LC 520, and the LC/Performa 550 have been revised and use a new battery, part number 922-0750. Your service provider will be able to determine which battery should be used.

** PowerBook 190 series includes the following models: PowerBook 190 and 190cs. PowerBook (Duo) 200 series includes the following models: PowerBook Duo 210, 230, 250, 270c, 280, and 280c. PowerBook 500 series includes the following models: PowerBook 520, 520c, 540, 540c, and 550 (550 sold in Japan only).

Where can I find more info about backup batteries for my Mac? - Some of the information on this page is based on the TIL (Tech Info Library) Article #11751, so you could look at that if you would like.