BullseyeBore Core uses two common LR44-sized coin cell batteries. Both batteries are mounted with the negative side pointing down towards the circuit board. We recommend the use of either Energizer 357 or Duracell 357 batteries. Standard LR44 coin cell batteries typically work with BullseyeBore Core, but do not provide as much battery life (durational use) as either Energizer 357 or Duracell 357 batteries.
Please follow the Setup section in the Quick Start Guide for instructions on battery installation including how to disassemble and reassembly the unit.