How to Make a 4.5v Replacement Battery for a Macintosh 128K, 512K or Plus (the text-only version)


A Cheap but Labor Intensive Way to Replace the Original Eveready No. 523 or Equivalent Clock Battery


With 4.5v compact Mac alkaline PRAM batteries becoming scarce, this project provides a working alternative to the single cell original batteries. If your browser can display graphics, you may find the illustrated version of these instructions, to be even more helpful (Hosted by the pickle's Low End Mac FAQ). By following this procedure you accept that you are doing so at your own risk and agree to hold me, the host of this page and everyone else in the universe, harmless for any damages or injuries it may cause. This should not be your first soldering project.




It helps to have a dead 4.5v cell to get the length right but it's darned close to 1 15/16". Very slightly longer (around 2") is better than slightly too short. You will need three new name-brand AAA 1.5v alkaline cells, solder, soldering paste, a soldering iron (high wattage is best), some insulated wire (larger gauge than phone wire but smaller than lamp cord) some transparent tape (electrical tape is too thick) and some CyA (Super) glue. You will be quickly soldering two small wires to the cells with a HOT iron. Everything else is easy.




Start by sparingly taping the three cells together in the middle so that two make up the approx. 2" length with a positive at one end and a negative at the other. The third is nestled exactly midway between the two so that looking at them from the ends, you have a triangle. The third cell should have it's ends opposite to the polarity of the closest cell end to them. This is easier to describe with the pictures. In other words, each end of the center cell should be opposite in polarity to the inboard cell end next to it. If you apply a drop of CyA (Super) glue between the cells, in the center, they won't be pushed together by the connectors with time and lose contact. Next, put a small amount of soldering paste on all the battery ends except for the extreme contact ends. Cut two short pieces of insulated wire, roughly 3/8" long and strip about 1/8" of insulation from each end. Put a little soldering paste on each end.


Proceed with restrained determination. With a HOT soldering iron, tin the four battery ends that are closest to the inside, leaving the extreme or contact ends alone. Try to do this quickly so the cells don't heat up too much. Using fine nosed pliers or forceps to hold the wires, solder them to both ends of the inside pairs of cell ends. You need to end up with three cells wired in series with a bare positive protruding slightly at one end and a bare negative protruding at the other. If you find that it is taking more than 4 seconds to solder a wire to an end, STOP and let the cell cool before you try again. When everything is soldered well, put some transparent tape over the soldered ends to prevent a short. Wrap some more tape tightly around the pack and you're done.


You should be able to fit the pack inside the holder if you didn't use too much tape. In my compacts, the lower, positive end is well inside the holder while the upper, negative end just contacts the connector. You may have to move it around a bit to get the optimal connection. The hatch will bulge slightly, holding the pack securely in place. If it doesn't want to stay closed, just leave it off. Barring a really hard knock, your pack should stay put without the hatch.


A Caution:


I have been using two of these packs in my compact Macs, for several months, with no problems, as I write this. Be aware that these early Macs apply current to the PRAM battery when they are turned on. Standard AAA alkaline cells are not designed to be charged. For this reason, you should use a well known brand of battery and periodically check your pack for any signs of leakage.


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