Sounds regulated to me, as long as I can recall Joye bats have come off the charger at less than 3.9V. Li-Ions typically charge to 4.2V. If you ain't seeing ~4.2V something is going on.... Of note, the eGo batteries I referenced are not regulated, and come off the charger at 3.7v. Same carto's that will not fire on these, work just fine on 900mah's.