Scantronic 9800 BF Error message

Hello People

Before i start yes i have done my reaserch and looked this error message up, but need more advice.

I have a Scantronic 9800 which keeps bringing up the error message of BF and i have to enter my user code to stop it but it keeps going off again.

Ok I need a short term fix so i cut the speaker cable but it is still making a noise from the key pad terminal thingy! I have read if I enter the engieenr code it will stop the error.

I have also read I need to replace the battery which is in the main control panel (in my loft) see how to below: (is this safe to do)?

Thanks Paul