A lot of people have their alarms set to 3.7v per cell (11.1v) for 3s. Depending on the load on your battery you may want to set it lower. I have an alarm that connects to the balance plug and goes off at 3.5v/cell, but once I land and there's no load on the battery the voltage rises to 3.7v/cell. Basically I just try to have a battery at 3.7v/cell when I'm done with it.