This Energizer MAX Plus 9V Battery will charge your devices for up to 50% longer than the 9V Energizer MAX. This battery is perfect for most standard smoke alarms and any other device that needs this type of battery. This battery can be used in a smoke detector, remote controlled car, portable radio, torch or other device. They can hold power for up to 5 years in storage. There is 1 9V battery in this pack.