Alpha Technologies XM3-HP Series - Technical Manual - Manual (Page 19)

19 017-882-B0-001 Rev. C2 (10/2013)
1.0
Introduction
1.2 Theory of Operation, continued
1.2.3 Charger Modes of Operation, continued
The Alpha XM3-HP uses a three-stage (other), four-stage (AlphaCell GXL), 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
1.0 Introduction, continued