You can buy a little charger for the battery pack. I bought one for mine about $10. If you can start the bike the pack should charge after a good ride. I don't remember getting any lights when the battery was low. My XR650R battery pack sat for 3 years no use charged up good and is being used and working for new owner.
Emgo 6/12v battery charger
Just realized BAJA Designs answered you . They should know.