The nine volt battery is a commonly available battery that is often used for smoke detectors. Identified by its rectangle shape, the 9 volt battery has a snap in connector, which can be convenient for linking several nine-volt batteries in a series, if necessary.
Although there is a common size for 9-volt batteries, there are size variations available, such as PP3 and PP9, allowing for higher charge capacities.
The rechargeable variation of 9 Volt batteries allows the battery to be re-used, often saving on expense over time, and creating a more environmentally friendly option than disposable batteries.
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