Old PRAM Batteries (Things that go bump in the night!)


Impending Doom

There’s one thing in particular inside your classic 68k Mac that’s sitting there like a time bomb ready to ruin your vintage machine. If you haven’t already guessed what it is, it’s the 3.6V “half AA” PRAM lithium battery.

When these things go, they don’t just “go” – they go out with a bang. The following is a story of my Macintosh Classic, it’s life, death, and afterlife.

What is this thing!?

The lithium battery inside a classic Mac is there to preserve PRAM settings while the machine is powered off. PRAM stores some settings information such as the date/time, start up disk, system volume, and some other basic settings.

Innocent enough, but after a decade or so these batteries can fail catastrophically! And unlike batteries in a TV remote, they don’t just leak – they literally explode.

My advice to any classic Mac fans out there, is to address the battery as soon as possible! If you purchased a classic machine off eBay, assume the battery is old and needs replacing. Or worse, if you had one since the beginning and you’ve never changed it – it’s time! I would suggest it’s better NOT having one in your system and just setting the clock when you boot up rather than taking your changes with a bad battery. As a rule of thumb, when I store a system for a long period, I take the battery out.

And now, onto the reason why…

A Macintosh Classic’s Tale


Above, is my beloved Macintosh Classic – both photos are of the same machine, just 20 years apart. This is a machine I’ve had… for a long time.

Around 2015 or so, I pulled the machine out of storage for a dose of nostalgia and to my surprise it was dripping fluid from the bottom! After opening the case up, I saw there was a perfectly-shaped sphere of corrosion around where the battery WAS located on the logic board. All of the bus lines on the board and near by components where unrecognizable and the metal surrounding the area looked like a rusty car frame in New England.

It was a victim of a PRAM battery bursting. I had the battery in there since it was new. I should have changed it back in 2000, never mind 2015!

I’ve since cleaned, treated, and painted the metal surfaces that were damaged and got a new logic board off eBay. So, the good news is, my Classic is alive once again. But tracking down components for 30 year old computers is getting harder and harder. Next time I store the Classic, you can bet I’ll be taking the battery OUT!


PRAM batteries can literally explode, don’t leave old ones in your Macs. It happened to me, and it can happen to you!