I have, the voltage is 3.5v, 7.1v, 10.7v, 14.3v, 17.9v, 21.5v, 25.1v, 28.7v, that's approximately 3.5v per cell. I have never fully depleted the battery, I once let the lights burn for about 4 hours and at that moment it was stille going strong. typically, I use my lights for about 2 hours max.