battery replacement

["tim@xxxxxxxxxxxxx" <tbil99@xxxxxxxxxxxx>]

I am renting a condominium and the main control panel of the security
system started beeping every 45 seconds. This seems to indicate that
there is a battery low in one of the wireless remote sensing devices.
There is only one device so I took the cover off of it but I cannot see
a battery. Any idea what I am doing wrong? I don't want to break
anything so I'm not prying anything off.
The system seems to be a Honeywell Ademco or something like that.

Any advice would be appreciated.