60 Freedom SW Owner’s Guide
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 32). The batteries are
maintained at the default float voltage level for the selected battery type or
the voltage selected under Float Voltage on the Custom Battery
Settings menu.
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.
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.
Freedom SW 3K2K InvChg Owners Guide.book Page 60 Wednesday, October 9, 2013 1:34 PM
