Rather than change batteries I built a power supply, wall wart, L7809CV and L7805CV. I scratched out simple traces on a Copper clad pcb. I mounted this in a clear plastic box I had on hand. Yesterday, I was alerted with a single weak beep, which is strange because it usually has 3 strong beeps. I checked for a customer, no customer, no birds, sometimes they trigger it. I happened to look up on the wall where the circuitry sets and there was a orange glow coming from the clear plastic box. My first thought, why did I put an LED in that? Then, I didn't put an LED in that. I immediately climbed up to the outlet near the ceiling and unplugged it. When I disassembled the unit, I noted condensation on the walls of the clear plastic container. The PCB had black growth between the input and ground leads of the L7809 and across the gap between traces. I think the glow was coming from the growth between the L7809 leads. This morning I cleaned all the corrosion from the PCB and parts, Powered the circuit and I have 9 volts and 5 volts as I should. The condensation was caused by water coming in an outdoor AC outlet through the conduit and dripping into the clear plastic box. This precipitated the corrosion growth and when it completed the circuit, started to glow the pretty orange color. I opened up the near by PVC conduit Tee connector and water dribbled out. So I have two repairs, the customer sensor power supply and water proofing the outdoor outlet. Glad I was there when it happened and not my wife. btw, this is on my boat.