The battery in the PDX & TQ10X Product is actually an integrated battery backed SRAM IC. This is a 64k Byte (8K x 8 bit) NV (non-volatile) SRAM (static radom access memory) that holds all the program memory. This SRAM chip is inserted into a socket on the controller printed circuit board, which is a small (approx. 2.5" x 4.5") PCB located on standoffs in the unit.
Dallas Semiconductor (acquired by Maxim Integrated Products)
web site: Dallas Seminconductor or Maxim Integrated Products
*Must use the "AD" part (Full +/-10% Operating Range), the "AB" part (Optional +/-5% Operating range) will NOT work
200ns access speed is preferred, faster access times are allowed.
web site: Digi-Key.com*