BIOS battery query

I have had a customer in today regarding his computer that I looked at over a month ago when the computer would not boot even after pulling out every device I could not get an error beep or any sign of life, well he came back and said that a friend of his fixed the problem by replacing the BIOS battery!?

I have seen a few things since being a technician but this is a first for me and for all the other guys they have never heard of a battery preventing a computer booting, showing a display oreven signalling beep errors.

Has anyone heard of a problem like this?