BOSS Compacts, as well as twin pedals, some loopers and some multi-FX processers, require a 9V power supply. The recommended power supply for the BOSS products that use a 9V supply, is the PSA Series*.
BOSS - PSA Series | Power Adaptor
Voltage and plug types differ by region. Please ensure that you use a regionally compatible AC adapter that matches your local power specifications.
Although there are a wide range of third party 9V power supplies available, we always recommend using a BOSS PSA series adaptor to avoid any malfunction to your pedal.
When using your pedals on battery power, a Carbon-zinc battery (9V, 6F22) or Alkaline battery (9V, 6LR61) will power your pedal.
BOSS compacts come with a battery already installed straight out of the box. Please be aware that this may not be fully charged, as it would have been installed for testing. Have a new battery ready to go when the original one runs out of power.