The CMOS battery is an essential part of a console as it powers the chip that stores important information and settings, like system date and time. In case of PlayStation consoles, a functioning CMOS is important for continued access to games, among other things. PS5 Pro CMOS battery slot is right under the console covers

My Playstation 3 has had a dead battery for years. Except asking me for the date every time I turn it on and asking me to reconnect to the PSN manually, I don’t see any inconvenience.