If multiple sets of batteries are connected in parallel to increase battery backup time, a cutting device must be provided so
that maintenance operations on one battery set will not affect the normal operation of the remaining battery sets.
Built-in lead-acid battery overtemperature alarm
For the type of built-in lead-acid battery, the temperature range when the service engineer uses the background software to
set the temperature must be between 55 and 60 degrees.
7.3 Battery Balanced Voltage
Battery boost charge
For lead-acid batteries, a manually initiated equalization charge function should be provided through the HMI to apply an
equalizing voltage to the battery.
Typical balancing voltage for lead-acid VRLA batteries is 2.35 VDC (selectable between 2.3 V/cell and 2.4 V/cell).
For lithium battery modules, battery equalization is passive equalization, which mainly occurs during charging. The battery
pack is balanced through the energy consumption mode of the BMS slave board MBB voltage divider resistor. The balanced
voltage is the real-time single-string charging voltage of the battery, and the highest balanced voltage is the charging cut-off
of 4.10 V.
7.4 Operation of Charger
APM2 should select charge logic and voltage thresholds for float mode and boost mode to prolong battery life and best
discharge performance.
For external battery cabinets, the charger will support temperature sensor feedback to adjust the charger current limit and
voltage settings to extend battery life.
The operation of the battery charger is described below:
• Phase 1 – While the battery is charging, the battery charger will be power limited. This phase of operation
continues until the battery voltage reaches a balanced voltage. The charger then transitions to the second stage.
• Phase 2 – The battery output is at float voltage during this phase. The charger transitions to stage three after a
time interval.
• Phase 3 - The output voltage will be pulsed at a certain time interval to maintain the float voltage until the battery
is discharged. This stage is used to check if the battery is connected. This is not part of the charging algorithm.
There is a BMS system inside the lithium battery module. After normal self-test and power on, when the battery is discharged
to 2.7 V of the cell, after the discharge is over, when the input power on the bus comes online, the inverter and charger will
automatically restart, and the BMS application will be in the current state. The current value is sent to the UPS, and the UPS
outputs instructions to the charger to charge the lithium battery module. The charging current is greater than or equal to 30
A, and the current flowing into the DC BUS high-voltage main circuit is guaranteed to be 30 A. When the battery is charged to
the 4.1 V monomer protection limit, the BMS sends a constant voltage charging mode for gradient down current. When the
charging current is less than a certain limit, the BMS sends a 0 A charging request current, the charger stops outputting, and
the single charging ends.
NOTE: The battery charger will only operate when the mains input has sufficient power remaining.
126 Proprietary and Confidential ©2023 Vertiv Group Corp. 7 Battery
Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual
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