Stage 4: Equalization mode
The purpose of the equalization mode is to remove the sulphation from the lead plates and to eliminate the stratification of the electrolyte. Approximately 2.5-2.6 volts per cell is applied to the battery with the charging current set to a very low value, typically less than 0.5 amp. The equalization mode may last anywhere from a few hours to over 24 hours depending upon circumstances.