I bought a pair of these First Alert model SA304LCN's a few months ago, installed one on 8/8/2009, and the other remained unopened on a closet shelf. Last night (10/2/2009) the installed unit started to chirp so today I removed the battery, tested it in a voltmeter, and found it to register in the "replace" range. Thus, I opened the still sealed unit and found that "Long-Life Lithium Battery" (10 year warranty, don'cha know) not only registering 0 voltage on the meter, but with corroded terminals. 100% faulty batteries. You can bet I will be calling the company first thing Monday. In the mean time, I certainly would recommend against purchasing anything from First Alert that includes a lithium battery.