I bought a used Osmo and the battery that came with it lasts about 6 minutes. I happened to plug the battery into the charger when the charger was not plugged in and the green light on the charger came on, I don't know if this supposed to be a feature (or if all chargers do this and I've never noticed?) but it seems as though the battery is trying to charge the my house. I ordered the external power cable and haven't been back to the battery so I never figured out if it was a battery or charger issue.