Retrofit Alarm Kit

My Retrofit Alarm Kit batteries only seem to last less then 12 months in a standard house (8 x PIR’s).

Is there a way to power it via a wall wart, or can some advise if it uses both batteries in series i.e. 6 Volts or are they in parallel i.e. 3 Volts?

Or does anyone have a schematic diagram for the device?