The X-Treme Summit 36V electric mountain bike complete 36 Volt 10 Ah LiFePo4 Lithium Battery Pack.
This battery pack is "easy swap", so you can either buy it as a replacement or a spare. Carrying a spare battery pack doubles your range! The Summit 36v battery can be charged while inserted in the bike, or externally at home or your office. One year manufacturer's warranty.
If buying one as a spare, keep in mind, these LiFePo4 battery packs need to be charged it at least once every 90 days to avoid capacity loss. See the Owner's Manual that comes with the bike for more information.