Question : Problem: need battery for Dell Dimension 4550

Hello,
My brother has a Dell Dimension 4550. It needs a battery.
Do you know the size?
I always thought most computers have same size battery on montherboard. Am I right?
I know I can open it up and look- but I am hoping to buy battery tommorow before I go over.

Thank you,

Answer : Problem: need battery for Dell Dimension 4550

How to replace the CMOS battery:
http://www.computerhope.com/issues/ch000239.htm