I have 2 dead batteries, and decided to see if I could remove the internal batteries and replace them with a external battery. They were both ST MK48T878-24 SRAM batteries. I cracked them open to see how things worked (before seeing Didier M's page). Below is a picture (albeit, a bad one) of the inner workings. One end has tabs for the oscillator (nearest pin 1), the other end, the battery.
The first one I removed nearly everything to see what was hooked up. It took about 20 minutes to carefully remove the potted part.
The second I only removed the battery part. This one only took about 5 minutes.
The saw works wonders. After cutting the chip in the middle, pry the top part (where the battery and oscillator are) and remove battery side. Carefully removing the remainder of the epoxy with the pliers and jewelers screwdriver. Solder connector using pliers. LOL. not fingers...
saw - http://www.sciplus.com/category.cfm?sub ... tegory=129
Jewelers Screwdriver - http://www.homedepot.com/prel80/HDUS/EN ... =100074336
klein d305-6 pliers - http://www.mytoolstore.com/klein/d304-6.html
very fine tip soldering iron and small header for battery connection. If you squint you can see the small header to the right of the chip.
Attached is the picture of the two chips...
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