How to Make a Replacement Rectangular Clock Battery with Connector

For your Macintosh (or PC)


Several models of Macintosh (and PC) require a rectangular 4.5v PRAM battery with a wire lead and connector. You can make a replacement from 3 AA alkaline batteries and the old lead and connector.

Original Battery & Replacement 

Note: Some Mac owners have had good results using commercial spring connector type plastic battery holders. It has been my experience that these holders almost always develop high resistance with time, corrode and fail. Soldering the cells is the most positive, failure proof way to connect them. It does require some previous soldering experience, as it must be done both quickly and provide a good "hot" joint.

1) Read the directions here. Substitute "AA" where it says "AAA" and disregard the measurements. Just lay the cells parallel to each other in a triangle with the ends even with each other then follow all other directions until you have three cells wired in series with a bare positive at one end and a bare negative at the other.

2) If the connection at the board is not marked for positive and negative, mark it on the board prior to removal (red is positive), then remove the old battery. Clip the lead wires from the old battery. Do this one lead at a time in case there is any life left in the battery. Clip them right next to the battery casing.

3) following the same directions you have just used for soldering in the other document, strip about 1/8" of the insulation from the ends of both the red and black lead wires. Solder the red lead to the positive end of your pack. Solder the black lead to the negative end of your pack.

4) *Important* Either cover the entire pack with heatshrink tubing or wrap it entirely in plastic packing tape. If the pack ever leaks, this is all that will protect your mother board from certain destruction. When the pack is covered, peel the old Velcro from the old battery and stick it to the new pack on one side with contact cement.

Your pack is now finished and ready to Velcro to the mother board where the old one was. plug the connector in, close the case and you are done. Don't forget to reset your Control Panels and read "A Caution" at the bottom of the other directions.

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