The Ultralife 9 volt lithium batteries (packed in foil) continue to work in a smoke detector for 8 to 10 years. Suitable for all devices that require a battery with an extremely reliable and long service life. Ultralife Corporation is a leading developer and manufacturer of a wide range of standard 9-Volt, Hirate ® Cylindrical and Thin Cell ® Lit., Li-ion and Lipo batteries.