PRAM battery in a 2012 MacPro 5,1

There is an anecdote:

do a PRAM Reset, by holding down the four keys:

command Option P R at startup.

continue holding those keys until it has completed chiming Four times.

failure to get to four times suggests the PRAM backup battery is getting weak.,

There is this measurement:

remove the side door, and remove the graphics card.

remove the battery and measure its voltage in your hand. voltages under 3.00 volts are considered 'spent"

There is this Preventative maintenance:

Just replace it with a CR2032, almost as good and readily available, cheap.

Normally, the parameters are maintained by an "always-on" power supply, as long as AC power is being supplied continuously. (e.g., not on power strip that gets shut off at night), and you did not recently MOVE your Mac (Read: drop the AC Power And move)

When AC power is not available, the PRAM backup battery is called into action to prevent corruption of the parameters that make day-to-day operation simple.

The PRAM backup battery is a non-recharging long-life lithium coin-cell.