Sure, you can but you may also purchase a replacement from Biktrix direct.
When you shop around, make sure you ask for batteries with premium Samsung or Panasonic cells. Another thing to look out for is to ensure the nominal voltage of the battery matches the nominal battery requirements of our bike. For example the Juggernaut mid-drives run on 48V batteries while some of the older Stunner(pre-2017) runs on 36V batteries. It is important to match the nominal battery voltage of the bikes.