The ALiEn2 and ALiEn2 Expert plunger lift controllers contain software that actively monitors the attached battery to determine when to go into a low battery shutdown to ensure the controller can perform critical operations and gracefully shut down.
Battery Monitor Operation
If 6 successive battery samples are below 5.5 V, the controller closes all valves and enters the Low state. A low battery alarm condition is recorded, which is reported in the history.
If 6 successive samples are above 6.0 V, the controller enters the Normal state. When entering the Normal state, the controller will restart to the Close state for a duration specified by the Close Time parameter.
Full Charged Battery
A fully charged battery will typically read 6.3 V as sealed lead acid batteries have three (3) cells with a capacity of 2.1 V per cell.
Please refer to this article on charging a battery.