CMOS battery low wrong memory on CMOS battery

Hi

My friends computer was coming up with the message

CMOS battery low.
And sometimes the PC would not start.

I installed a new battery( correct one)

The computer didn't start, so I reinstalled the old one.
The computer then started but with the message, CMOS battery low.

So I again reinstalled the new battery, this time the computer started but
with the error,Wrong memory on CMOS battery.

Since then the computer has started normally, not at all, or with a
combination of, or both, CMOS battery low and Wrong size memory.

Any ideas what is the problem?

 

Carefully remove the *cell* and with a DVM, measure to see if the
voltage is 3.00V or maybe a little more.
If it is lower (say 2.98V or less), then it needs replacement.
Read the voltage on the original cell as well.
Before re-inserting the cell, find the CMOS jumper on the board
("clear CMOS") and move the jumper over to the opposite position, wait
15 minutes, and move it back to the default position.
Put in a cell that measures 3.00 volts or more and re-try; should be
OK now.
You may have to use the BIOS menus to re-apply desired settings.