Alpha Technologies AlphaCell HP - Manual (Page 23)

23 745-680-C5-002, Rev. A
Fig. 8, Charger Modes (dashed line indicates 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:
The following information specifically pertains to Alpha XM Series 2 and HP Power Supplies.
4.1 Alpha Power Supply Charging Profile
BULK charge is a “Constant Current” charge. This current is the maximum the charger
is capable of delivering: 10A for 615, 906/915/915HV, and 922/922HV. As the charge is
returned to the batteries, their voltage increases to a specific threshold (2.27Vdc per cell).
The BULK charger mode generally returns the battery charge state to 80 percent of rated
battery capacity. Bulk mode is not temperature compensated. The charger then automatically
switches to ACCEPT mode.
ACCEPT charge is a “Constant Voltage” charge. This voltage, 2.2-2.45Vdc per cell, is
manually adjustable if needed and 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 charge, averaging about 2.1-2.35Vdc
(adjustable) per cell. During FLOAT mode, the batteries are fully charged and ready to
provide backup power.
During ACCEPT and FLOAT modes, the cell voltage is temperature-compensated at
-0.004Vdc per cell per degree C (adjustable) to ensure a safe battery cell voltage and to
maximize battery life.
For AlphaCell HP batteries, the recommended battery system float charge voltage is equal
to the number of cells in the system multipled by the range of 2.1 to 2.35 volts per cell at
77°F(25°C).
For example, float charge a string of 3 each 12 volt (6 cell) batteries within a range of 37.8 to
42.3 Vdc (18 cells x 2.1 V/C minimum and 18 x 2.35 V/C maximum) at 77°F(25°C).
Severe overcharging over extended periods of time can induce a thermal runaway condition.
This requires replacing the battery system.
4.0 Battery System Float Charging, continued