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Battery Charging Reference
Absorption Stage
During the absorption stage, the Freedom SW begins operating in
constant voltage mode and the current falls gradually as the amp
hours are returned to the battery. By default, the bulk and absorption
voltage settings are the same for all battery types. The voltage limit
settings for bulk and absorption can be adjusted independently if the
battery type is set to Custom.
Once the Freedom SW reaches the Bulk (Absorption, after the
first 60 minutes) Voltage setting, the Freedom SW will operate in
constant voltage mode, providing only the necessary current to
maintain the voltage setting. As the amp hours are returned to the
battery, the current required to maintain the voltage setting falls
gradually.
The Freedom SW transitions to the float stage if either one of the
following two conditions are met:
1. The charge current allowed by the batteries falls below the exit
current threshold, which is equal to 2% of the programmed
battery capacity (for a 500 amp-hour battery bank, this would
be 10 amps), for three minutes.
2. The Freedom SW has been in absorption for the programmed
maximum absorption time limit. The default is 3 hours, but the
time limit is programmable from 1 minute to 8 hours.
Float Stage
Float charge maintains the batteries slightly above the self discharge
voltage of the batteries. The charge current in float is the current
necessary to maintain the batteries at the Float Voltage setting,
limited only by the inverter's capability or other settings that limit
the inverter's maximum charge rate. Float charging reduces battery
gassing, minimizes watering requirements (for flooded batteries),
and makes sure the batteries are in a constant state of readiness.
When three-stage charging is selected, the charger automatically
switches to the float stage after the batteries have received a bulk
and absorption charge (see Figure 35). The batteries are maintained
NOTE: If there are DC loads on the batteries, the charger’s current may
never decrease to a level to initiate the next stage of charging. In this case,
the charger would stay in absorption until the Absorb Time setting is
reached.
NOTE: To make sure the charger does not remain in absorption for too
long, adjust Absorb Time on the Charger Settings menu. The timer
begins at the start of the absorption stage and terminates absorption
charging if the charge current does not decrease to below 2 per cent of the
battery capacity before the Absorb Time setting expires. The Absorb
Time setting may be increased if the charge cycle continually runs the full
Absorb Time in the absence of DC loads. This is an indication of too
large a battery bank for the selected Absorb Time setting.
Freedom SW 3K2K InvChg Owners Guide.book Page 65 Thursday, July 31, 2014 1:42 PM