Not having such a device, why would the *receiver* be battery powered
unless you live somewhere without mains electricity?
Bells/chimes here in the U.S. when hooked to main power in my
experience use a transformer to step power down to low voltage
12 or 24?). This obviates armoring the wires and makes wiring easier,
plus provides fatal shock protection for a hapless doorbell ringer
who might be standing on a wet welcome mat. Welcome - ZAPPP!
The wireless units are much easier to install, and can be located
anywhere with no connections but a couple nails or screws.
In my experience the battery for the button lasts a minimum of 2 years
and for the chimes even longer. The button takes an AAA and the
inside probably one or two C's.
I live near Chicago where winters are typically cold. The outside
button never gets wet as it is protected by a porch awning.
The bell/chime is little used, maybe averaging once a week.
I put this in about 10 years ago.
I wouldn't buy a unit that uses anything but common batteries.
--Vic