Battery Charging - Siemens 667/HB/47750/000 General Handbook

12.4 Battery Charging

The Alpha FXM UPS unit has four specific has four specific modes for battery charging
that are automatically cycled according to the battery pack voltage and State of Charge.
These are described below.
NOTE: All values given in the descriptions below apply to a UPS Solution
operating at an ambient temperature of 25°C. See section 12.5.2 for details on
temperature compensated battery charging.
Bulk Charging -
Absorption -
Float -
Charger Off -
Figure 12-4 displays the battery charging cycle in terms of voltage and charging current.
WARNING: Even with no battery packs connected, if mains power is available
a voltage of 32Vdc is normally present at the Alpha FXM UPS Unit's battery
terminals. This is voltage is periodically raised to 56Vdc or above as the UPS
unit looks for a battery connection.
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Used to recharge the batteries after discharge. The
charger within the FXM UPS unit operates in constant
current mode with an upper limit of 10Amps. The target
battery voltage is set to 54Vdc (2.25V per cell). The battery
voltage rises steadily as the batteries charge. As the battery
voltage approaches its target voltage value, the current
drawn starts to decrease. The charger voltage is then held at
54Vdc and the charger moves into Absorption mode.
Used to complete the final stage of battery recharge. The
charger is now in constant voltage mode and holds the
battery voltage at 54Vdc. The battery pack is allowed to draw
current based on its capacity and chemistry. The current
drawn continues to decreases as the battery charges.
Used to maintain fully charged batteries. As the battery
pack nears full charge, the current drawn drops to roughly
1A. The battery voltage is held at 54Vdc. If the current drawn
is roughly 1A or less for 10 to 20 minutes, the FXM UPS
Unit's battery charger moves to the next state.
Used to monitor the battery pack and check for any
faults. The battery charger switches itself off on leaving Float
mode. If the battery pack is bad or faulty, its voltage will drop
rapidly and the FXM UPS unit's 'Bad Battery' alarm is
triggered. If the battery pack is in good condition, the battery
voltage will drop slowly. When the battery voltage drops to
52.6Vdc, the charger switches back on and enters Bulk
Charging mode.
Page 52 of 76
TS008468
Infrastructure and Mobility, Traffic Solutions
Sopers Lane, Poole, Dorset
Status ISSUED
Date 31/01/2017
Doc. No. 667/HB/47750/000
BH17 7ER