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2001 Xantrex Technology, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. C: February 2001
CHARGER MODE
IN BRIEF
When AC power is available, the inverter can operate as a very powerful battery charger with low current
distortion. Power is drawn over the full AC cycle. This improves the performance with low AC input voltage
or with small generators.
The SW Series Inverter/Charger includes the ability to automatically “back-off” the battery charger to
prevent overloading a generator or tripping a circuit breaker when other AC loads are being operated
through the inverter. This improves system reliability and allows greater use of the power available. The
charger will also be turned off if the AC voltage drops to an adjustable lower limit VAC setting.
THREE STAGE CHARGING PROCESS
The charging cycle uses three stages. During the initial "Bulk Charge" stage, the inverter charges at
maximum rate allowed by the SET MAX CHARGE AMPS AC setting. This causes the battery voltage to
rise over time. After the battery voltage nears the SET BULK VOLTS DC setting, the charger starts the
second or “Absorption” stage. During this phase, the charge rate is gradually reduced while the battery
voltage is held near the bulk voltage setting. This ensures that the battery is fully charged. The final "Float"
stage is initiated when the battery has been held near the SET BULK VOLTS DC setting for the
adjustable ABSORPTION TIME period setting. At this point, the battery voltage is allowed to fall to the
FLOAT VOLTS DC voltage setting, where it is maintained until another bulk charge cycle is initiated. This
reduces gassing of the battery and keeps it fully charged. A new three-stage charge cycle is initiated after
an AC source is reapplied to the AC HOT input terminals, or daily if the BULK CHARGER TRIGGER
TIMER (15) is enabled and if AC power is available continuously.
Figure 21, Three-Stage Battery Charging
AC SOURCE CHARGER BATTERY
AC DC
If a generator was started automatically by the
inverter to charge the battery, it will be shut off when
the charger reaches the float stage after the
bulk/absorption period. (GENERATOR must be in
AUTO mode)
Bulk Stage Absorption Stage Float Stage
DC Voltage
AC Current
Constant Current Reduced Current Reduced Current
Bulk Volts Setting
Float Volts Setting
Time
Max Charge Amps
Setting
Absorption Time
Charging
Started
Increased Voltage Constant Voltage Reduced Voltage