I believe I have a defective unit.
It has been 4 weeks since the chirping stopped. At that time, I put in new Rayovac UltraPro Alkaline Batteries, even though I had new batteries in the unit form the original install. Now the unit is saying, “the batteries in this unit needs to be replaced immediately”.
Being in business, I understand sometimes defective units make it into the market place. I believe Google should replace this unit.
@JillG, thanks for the help!
@PhilipR, Like what JillG mentioned, Both battery and wired Protect require Energizer Ultimate Lithium AA (L91) batteries. Let us know if you're still experiencing the issue once you installed the recommended batteries to your Nest Protect. You can also click on this link to learn more about this.