I have a number of battery powered, low-power consumption zwave sensors installed around the house, such as contact, PIR or temperature sensors. These are most running on 3v (CR123 or 2 AAA) batteries and takes very little power ( one set of battery lasts for 3month to 1 year.. so maybe < 10ma? )
I am thinking of modifying some of them, to put hole in the battery cover so I can wire it to a 12v wall wart with a buck converter outputting 3V near the sensor. The wire may or may not go through attic/drywall/exterior wall, but the wall wart / buck converter will be accessible, and there will be connectors and fuses to break the circuit.
I read about the regulations and safety concerns, and learned that for low-voltage wiring I would want CL2 for in-wall use, and I should worry about voltage drop for longer runs ( which the buck converter should mitigate). It seems like NEC does not specify too much in the class 2 area?
What am I missing? Is there other related NEC for this kind of setup? What are the regulatory and safety concern should I worry about in this setup? Is this a viable plan?