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66 Freedom SW Owner’s Guide
Battery Charging Reference
at the default float voltage level for the selected battery type or the
voltage selected under Float Voltage on the Custom Battery
Settings menu.
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: The battery voltage can increase above the float voltage when
using an external charging device such as PV arrays, wind turbines, and
micro-hydro generators. Be sure to include appropriate charge
management equipment with all external DC sources.
NOTE:
If the AC input fails or drops below the lower VAC limit (as set in
AC Settings
), the complete multistage 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.
Figure 36 Two-Stage Charging Cycle
Time
Time
Absorption Voltage
Max Absorb Time - Dflt 3 hrs
(adjustable1min-8hrs)
2-Stage Charge
AbsorptionStage
BulkStage
Recharge
Voltage
Battery
Voltage
Battery
Current
Max Charge
Rate
Return to
Bulk Stage
Absorption Exit Current
Threshold = 2% of
programmed AH capacity
Freedom SW 3K2K InvChg Owners Guide.book Page 66 Thursday, July 31, 2014 1:42 PM