As batteries near full capacity, charge current decreases. End Amps, Return Amps, or Tail Current refers to the lowest output of current (Amps) flowing to the batteries as they have reached full capacity. Some chargers will determine this set point has been reached by monitoring current output to the battery bank. If the charge current drops, reaching the End Amps/Return Amps/Tail Current set point before the programmed Absorption time has completed, this will trigger the charger to shut off or switch to the Float voltage phase which holds the battery bank at 100% SOC. The charger will complete the full programmed Absorption time if this set point is too low or programmed at 0%.
The recommended End Amps/Return Amps/Tail Current set point for Rolls Flooded models is 2% of the 20 Hr AH rating (C/20) of the battery bank. Typically, when current drops to the 2% set point for 1 hour the battery bank has reached 100% SOC.
Rolls Flooded models with Advanced NAM may have a slightly higher End Amps/Return Amps/Tail Current set point as the cells are less resistant to charge and current output will remain slightly higher at 100% SOC. (2% recommended, 2-5% range) An adjustment to this set point may be required when these models replace other Flooded batteries. Test specific gravity at Float Charge to confirm 100% SOC.
WARNING: The End Amps/Return Amps/Tail Current setting, combined with a sulfated battery, may confuse the charger as added resistance will reduce the flow of current. This may falsely trigger the charge to end the Absorption charge prior to reaching 100% SOC. Test specific gravity regularly to confirm the battery bank has reached 100% SOC and adjust this set point and/or Absorption time as necessary.