This sets the number of hours the plant applies its elevated 'equalize' charge voltage to the battery string during a periodic equalize cycle, per the description. Equalizing is a maintenance charge held above the normal float voltage specifically to reverse cell-to-cell imbalance in a VRLA or flooded battery string, so leaving this duration too long risks overcharging and gassing the batteries even though the cycle is meant to extend their life. A value of 40 means the equalize voltage is applied for 4.0 hours during each equalize cycle.