Creating a new battery group can be done as follows:
Head to Battery Storage
Click Add new group
Fill in the name for the organization
Select owner organization for the group (if your organization has sub-organizations)
Click Save once you are ready.
Your group will appear in the table displaying all your battery groups. The groups are by default organized in alphabetical order. If you have a lot of groups, try using the search field in order to verify your group was properly added.