Know the difference between U9VL and U9VL-J
Ultralife U9VL – 9V Lithium Battery, Plastic Housing
U9VL is the model number for the Ultralife 9 v lithium battery using a plastic housing. It is sold only in sealed foil packaging as model U9VL-FP. An advantage of the sealed foiled package, which must be torn open to remove the 9 volt lithium battery, is to be able to verify that the 9 v lithium battery has never been used. The Ultralife 9 v lithium battery is designed for applications in which the battery will most likely be used fairly quickly, such as in many medical, wireless security and music/audio devices.
Metal Casing Lithium Battery
U9VL-J is the model number for Ultralife long-life 9 volt lithium battery. It is actually an Ultralife 9 volt lithium battery encased in aluminum housing. The aluminum housing reduces the amount of moisture that can enter the battery over time, which enhances its life. It is also slightly larger than the U9VL (U9VL-FP) battery and may present a tighter fit in a small number of devices with smaller battery compartments that were originally designed to match the dimensions and shape of an alkaline battery, which has more rounded edges. The U9VL-J is designed for applications in which the 9 v lithium battery must either last a long time, such as in smoke alarms, or where it may be exposed to low temperatures or uncontrolled heat and humidity conditions, such as in electronic parking meters or other outdoor applications such as automatic watering systems and dog training transmitters.
Note for Wireless Mic Users
When to choose metal casing over plastic casing when selecting a 9 volt lithium battery? The metal casing is excellent for outdoor applications and high moisture situations. Smoke alarms can use either version.
The metal casing 9 volt lithium battery is not suitable for wireless microphone use due to the size of the battery casing. Battery cavity fit will be problematic. Choose the plastic version of Ultralife 9 Volt for wireless mics.