From Fishman:

This battery pack is a direct-fit replacement for the back/vibrato cover on a Strat. The ideal power solution for Fishman Fluence pickups, these lithium-ion packs require no modification of your guitar, and can also be used to power other on-board 9-volt pickups and accessories. Featuring a current capacity similar to a premium 9-volt alkaline battery, this battery pack is rechargeable via a standard mini-USB cable. The cable is included in the box. LED indicators let you know when the battery pack is full, and when its time to recharge. Complete recharge time from empty is 3 hours or less, and a full charge offers weeks, not hours, of playing time between charges (depending on load). Strat is a registered trademark of FMIC.

FISHMAN FLUENCE RECHARGEABLE BATTERY PACKS INCLUDE:

• Connection wire
• Micro-USB cable