2.1.2 Coordination of Charging Dry Contact Signals with UPS Protection Mechanisms
The UPS prioritizes dry contact signals above all else, charging or stopping charging based on these signals. The UPS further incorporates a two-tier protection mechanism to prevent unexpected battery failures caused by abnormal dry contact signals.
Figure 2.1.2.1 Charging Protection Logic Diagram
A. When the BMS dry contact signal is normal, if an overcharge alarm occurs within the battery pack (e.g., voltage reaching 3.5V/cell for any cell) or an over-temperature event triggers a charging stop, charging dry contact signal 1 activates, causing the charger to immediately cease charging output.
B. The BMS also cuts off charging input when any cell reaches 3.65V/cell.
C. If the BMS dry contact signal fails to transmit normally or the transmission line is interrupted, the UPS continues charging. However, when the entire pack reaches 3.6V/cell per series, the UPS CPU executes software protection, shutting down the charger output.
D. If both the BMS dry contact signal and the UPS CPU fail or the command channel becomes abnormal, the charger's independent hardware control circuit will limit the charger to 3.65V/cell for the number of series cells.
2.1.3 Discharge Dry Contact Signal
The dry contact signal 2 output from the battery pack BMS is defined as the discharge dry contact signal. A normally open signal indicates permitted discharge, while a normally closed signal indicates prohibited discharge.
The BMS discharge dry contact signal activates upon abnormal alerts such as undervoltage or overtemperature. For example, when discharge reaches 2.9V/cell, the BMS discharge dry contact signal state changes from normally open to normally closed.
After discharge ceases and the battery voltage recovers above 3V/cell, or after all other abnormal alarms are cleared, the BMS discharge dry contact signal status changes from normally closed to normally open.
2.1.4 Coordination of Discharge Dry Contact Signal with UPS Protection Mechanism
The UPS treats the discharge dry contact signal as the highest priority. It permits or halts battery discharge based on this signal instruction. The UPS further incorporates discharge protection actions to prevent unexpected battery failures caused by abnormal dry contact signals.
A. When the BMS dry contact signal is normal, if an overcharge alarm occurs within the battery pack (e.g., voltage reaching 2.9V/cell for any cell) or abnormal events like overcurrent or overtemperature necessitate stopping discharge, the discharge dry contact signal 2 activates, causing the UPS to immediately cease charging output.
B. The BMS also cuts off discharge output when any cell reaches 2.8V/cell.
C. If the BMS dry contact signal fails to transmit normally or the transmission line is interrupted, the UPS will continue discharging. However, when the entire battery pack reaches 2.85V/cell* (per series), the UPS CPU executes software protection and stops discharge output.
D. If the UPS is in mains power mode (not requiring discharge) and receives an abnormal discharge dry contact signal, it will trigger a "Battery Abnormal" alarm.
Figure 2.1.4.1 Discharge Protection Logic Diagram