Alpha Technologies XM2, XM2-HV, XM2-HP - Manual (Page 17)

1.1 Theory of Operation, continued
1.1.3 Charger Operation
The Intelligent CableUPS uses a three-stage, temperature-compensated battery
charger. During AC line operation, the inverter winding on the ferroresonant
transformer feeds the charger circuit which provides BULK, ACCEPT and FLOAT
charge voltages to the batteries.
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 batteries 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 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. 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. 1-4, Charger Modes
(dashed lines indicate HV models)
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:
On HP models, when Alpha Cell is the selected battery type, ACCEPT and FLOAT are pre-set and are
not manually selectable.
17 017-805-B0-010 Rev. K2