Being that you didn’t specify which computer you actually had, no one knows the answer. It’s easy to unscrew the back and head to a jewler to get a new battery though. Most are regular watch batteries, but they vary in size so take the old one with you or write down the number. Don’t ask for the standard battery, as there is not one.
I just took my old one out and took it to wal-mart/target which ever store and picked up a replacement (matched battery model number)and popped it back in. Works good as new. Mine is the Specialized Pro that is 3 yrs old.
Tom