19
017-882-B0-001 Rev. E (06/2018)
1.0 Introduction, Continued
The Alpha XM3-HP uses a three-stage (OTHER battery type), four-stage (AlphaCell GXL and XTV), or five-stage (AlphaCell
HP) temperature compensated battery charger as determined by the type of battery used in the system. During AC line
operation, the inverter winding on the ferroresonant transformer feeds the charger circuit which provides the appropriate
charge voltages to the batteries.
3-Stage Charger Modes (BULK/ACCEPT/FLOAT):
The 3-stage charger is applied when the battery type of OTHER is selected in the Smart Display menu.
BULK charge is a “Constant Current” charge. The maximum current is 10A. As the charge is returned to the batteries,
their voltage increases to a specific threshold (2.40VDC per cell). The charger then switches to ACCEPT mode. The BULK
charger mode generally returns the battery charge state to 80 percent of rated battery capacity.
ACCEPT charge is a “Constant Voltage” charge. This voltage, default 2.40VDC (programmable 2.20-2.45VDC) per cell, is
temperature-compensated to ensure longer battery life and proper completion of the charge cycle. This cycle is complete
when the charging current into the batteries becomes less than 0.5A or approximately six hours elapses from the time
ACCEPT mode was entered, at which time the charger switches to the FLOAT mode of operation.
FLOAT charge is a temperature-compensated charge, default 2.27VDC (programmable 2.10-2.35VDC) per cell.
During FLOAT mode, the batteries are fully charged and ready to provide backup power. The charger provides a small
maintenance charge to overcome the batteries self-discharge characteristics and other minor DC loads within the power
supply.
Battery Voltage
Battery Current
BULK
Constant
Current Mode
(10A max) until
battery voltage
reaches the
ACCEPT level
(2.40V/cell)
ACCEPT
Constant Voltage Mode
(2.40V/cell) until battery
current demand drops
below .5A or time out
based on 4 minutes per
Ah battery capacity
FLOAT
Constant
Voltage Mode
(2.27V/cell)
Fig. 1-2, 3-Stage Charger Modes
