I will admit that I have been fortunate until recently which led to being lax about removing PRAM batteries from the computers that come in. Well, it has finally caught up with me and a ROM 3 Apple IIGS.
The alkaline batteries that are in the early compact Macs can and will leak over time – we have all see that in other devices that we use every day. Fortunately, the Battery compartment is exterior on the back of those Macs, so shielding the potential mess from the interior of the computer.
Starting with the Macintosh II series all the way up to the G5 and including the Apple IIGS, most use a 1/2AA 3.6V Lithium battery used to keep our settings and the time and date among other things. While there are many many manufacturers of these batteries, the most urgent ones to find are the red Maxell pictured below. They can and have and do explode! Many of the others may or may not eventually start to leak.
Looking around the internet after the fact, this is a common issue and well documented on the 68mla.org site. Unfortunately, it will take me time to catch up to every Mac and IIGS that I have here in inventory and remove the batteries, so I hope for the best. So many I have already removed are the original batteries dated in the late 80’s.
If you use any of these computers regularly, please just replace the batteries when they are no longer doing their job. For the rest of us that don’t use our treasures very often, or may have them buried in the attic or basement, it is past time to remove these batteries before they destroy our computers.
There are a few Macs that will not boot without a PRAM battery or will show odd symptoms when it needs to be replaced, so that should be one of the first things you check.
By the way! This is also a good time to look at the regular battery on your Portable, PowerBook, iBook, and MacBook model that you may have to make sure that they don’t show signs of swelling.