ADLINK cPCI-6620 - Manual (Page 27)

Functional Description 15
cPCI-6620
3.5 Battery
The cPCI-6620 is equipped with a 3.0V "coin cell" lithium battery
for the Real Time Clock (RTC). The lithium battery must be
replaced with an identical battery or a battery type recommended
by the manufacturer. A Rayovac BR2032 is equipped on board by
default.