per cell is 2.1V x 6 = 12.6V....minimum voltage of a battery with engine off is 12.6V....safest maximum is 14.4V. maintain it at greater than 14.4V and you will kill the battery (added problem in this case). Battery fluid will be lost and lamps usually burn frequently. The usual culprit is the IC inside the alternator (if built-in IC). what happened in my case is a burnt stator coil aside from a broken IC. i settled with a surplus unit.