Xantrex Technology 815-2024 Two-StageCharging Process, Battery Charging Reference, 97-0019-01-01

Freedom SW 3K2K InvChg Owners Guide.book Page 61 Wednesday, October 9, 2013 1:34 PM

Battery Charging Reference

Two-Stage Charging Process

Two-stage (or no float) mode differs from an ordinary three-stage charge mode in that it does not continuously maintain the battery at float voltage. Instead, the Freedom SW begins charging the battery in bulk mode whenever the battery voltage drops below the recharge level. While the battery voltage is above the recharge level the inverter’s AC transfer switch continues to pass power through from the utility grid to the loads, but does not actively charge the batteries.

Two-stage mode increases efficiency of utility connected systems by reducing the amount of power consumed by the inverter and batteries compared to when the battery is continuously maintained at Float Voltage. This feature can extend the life of most batteries.

NOTE: If the AC input fails or drops below the lower VAC limit (as set in AC Settings), the complete multi-stage charge cycle (bulk, absorption, float/no float) restarts once the source AC recovers to within the acceptable range. If the batteries are already nearly full, the charge cycle will take little time to complete.

Bulk Stage	Absorption Stage
Battery
Voltage	Absorption Voltage
	2-Stage Charge
Recharge
Voltage
	Return to
	Bulk Stage
	Time

Max Absorb Time - Dflt 3 hrs (adjustable 1 min - 8 hrs )

Battery

Current

Max Charge

Rate

Absorption Exit Current

Threshold = 2% of programmed AH capacity

Time

Figure 33 Two-Stage Charging Cycle

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