Our on-site tests indicate that the battery included with your Z-Vibe will last for a minimum of 24 hours of continued use (and usually longer). When it is time for a replacement, this is the battery you need.
Note that while this battery is similar in size to a standard AAA battery, the two are not identical. Standard AAA batteries will not power the Z-Vibe, and will usually get stuck inside the device (rendering it useless).
