Good deal on EXPIRED units. The recommended life of these batteries is 3 years. The date code on the box and the batteries in the unit is December 2016. Haven’t installed these yet. Will test first, but if you buy, plan on also buying new batteries. These are 3.6v 900mah nicad packs, replacements are about 9 bucks on amazon.
Also note that the instructions describe the maximum mounting height for these is 8 feet. Something to keep in mind if you have high ceilings.
After testing both units that I bought seem to work fine. I let them charge for 24 hours as recommended, and then turned off the power. I let them run for 15 minutes. They were still going strong after 15 minutes, so that is good enough for my needs.