In article ,
Al writes:
Could it be that one or both of
the batteries needs to be changed?

Sounds like the panel one needs replacing, and possibly the bellbox too.

They are *supposed* to be changed regularly, whne the system is 'serviced'.
Frankly, nobody bothers ;-)

Battery life depends heavily on the quality of the charging circuit,
and the number of times you've had it run too flat. (A larger capacity
battery is less likely to run flat during a typical power cut.)

Commercial alarms often include a daily battery test cycle, and can
include circuitry to protect against running the battery too flat.
I don't know if these features are found in domestic alarms, but I
suspect certainly not cheaper ones. It could also be that commercial
alarms may have better quality charging circuits.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]