Alpha Technologies XM2-300CE-HP - Manual (Page 15)

1.1 Theory of Operation, continued
1.1.3 Charger Operation
The XM2-300HP uses a three-stage, temperature-compensated battery charger.
During AC line operation, the inverter winding on the transformer feeds the charger
circuit which provides BULK, ACCEPT and FLOAT charge voltages to the battery.
Charger Modes
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
(2.27Vdc 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, 2.40Vdc (adjustable)
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 battery becomes less than 0.5A, or approximately six hours elapses from the
time ACCEPT mode was entered. When the batteries are fully recharged the charger
switches to the FLOAT mode of operation.
FLOAT charge is a temperature-compensated “pulsed voltage” charge, averaging
about 2.27Vdc (adjustable) per cell. During FLOAT mode, the battery is fully charged
and ready to provide backup power. The charger provides a small maintenance
charge to overcome the battery self-discharge characteristics and other minor DC
loads within the power supply. As the battery voltage reaches the “full charge” level
the time delay between pulses increases.
During ACCEPT and FLOAT modes, the cell voltage is temperature-compensated
at -0.005Vdc per cell per degree C (adjustable) to ensure a safe battery cell voltage
and to maximize battery life.
Fig. 1-3, Charger Modes
1
2
3
4
5
6
7
8
9
10
2.15
2.25
2.05
2.40
0
Volts Per Cell
Charger Current
Bulk Accept Float
NOTE:
When AlphaCell is the selected battery type, ACCEPT and FLOAT are pre-set and are not manually
selectable.
15 017-877-B1-001 Rev. A