While some older keyboards have batteries to store basic, operating system information (similar to CMOS) this is no longer the case. Most keyboards did away with batteries about 10 years ago and opted to go with chips that store this information without requiring battery power. So, with luck, you may have a board that no longer relies on a CMOS battery. If not, one day it will die. The only way to find out is to check the schematic diagram of the kayboard, or call the manufacturer's customer service department.
Good Luck,
Gary
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Travlin' Easy
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)