Battery Backup and Alarm Monitoring Functions
The MEAN WELL DRS-480 Series integrates AC/DC power conversion, battery charging, DC UPS backup, battery management and system status monitoring in a DIN rail design. It is intended for security systems, fire detection and fire alarm systems, emergency lighting, public safety battery backup, central monitoring and other applications that require continued DC power and supervised battery backup operation.
When AC mains is available, the DRS-480 Series supplies power to the connected load while charging the external battery. If AC input fails, the built-in DC UPS function switches the load to battery power within 10ms, allowing critical equipment to continue operating without a separate external DC UPS module.
All DRS-480-24, DRS-480-36 and DRS-480-48 models provide AC Fail, DC OK, Battery Low / Abnormal / Disconnected and Charger Fail status signals through Form-C relay contacts. The relay contacts support a maximum rating of 30VDC / 1A.
Battery Backup Operation
The DRS-480 Series is designed for direct integration with an external battery. During normal AC operation, the power supply provides energy to the connected load while charging the battery at the same time.
When AC mains power fails, the DC UPS function automatically transfers the load to the connected battery. The transfer occurs within 10ms according to the datasheet, allowing the DRS-480 Series to function as a DIN rail power supply with battery backup for security, fire alarm, emergency and monitoring systems that must remain operational during temporary AC power interruption.
The series also supports Battery Start, allowing the system to start directly from battery power without requiring AC input.
Maximum battery charging current is 15.4A for DRS-480-24, 10.2A for DRS-480-36 and 7.7A for DRS-480-48.
AC Fail Alarm Signal
The AC Fail relay output allows an external monitoring system to detect loss of AC mains input.
According to the DRS-480 alarm logic, the AC Fail relay provides Form-C contacts and changes state when AC input falls below the specified detection range. The datasheet specifies AC failure detection at approximately 79–89VAC for a 120VAC system and 132–187VAC for a 220VAC system.
The relay contact is rated up to 30VDC / 1A and can be connected to alarm panels, controllers or monitoring equipment for AC mains supervision.
DC OK Status Signal
The DC OK signal provides supervision of the main DC output.
The datasheet states that DC OK is activated when the output voltage is greater than 90% of the rated value. The Form-C relay output is ON when DC output is normal and OFF when a DC failure condition is detected.
This allows external controllers, alarm panels or central monitoring systems to verify that the DRS-480 output remains within its normal operating condition.
Battery Low / Abnormal / Disconnected Signal
The Battery Low / Abnormal / Disconnected relay output monitors the condition of the connected backup battery.
Battery Low thresholds vary by model:
- DRS-480-24: below 22 ±0.3V
- DRS-480-36: below 33 ±0.4V
- DRS-480-48: below 44 ±0.5V
The relay changes state according to battery condition, allowing security systems, alarm panels and monitoring controllers to detect low, abnormal or disconnected battery conditions before backup capability is lost.
Battery Cut-Off Protection
To help prevent excessive battery discharge during extended backup operation, the DRS-480 Series includes battery cut-off protection.
The specified battery cut-off levels are:
- 20.9 ±0.5V for DRS-480-24
- 31.3 ±0.7V for DRS-480-36
- 41.8 ±1V for DRS-480-48
Battery cut-off works together with battery status monitoring to protect the connected battery during prolonged backup operation.
Charger Fail Alarm Signal
The Charger Fail relay output provides dedicated supervision of the battery charger circuit.
The Form-C contact is ON when the charger is operating normally and OFF when a charger failure is detected, allowing external monitoring equipment to distinguish a charger fault from AC input, DC output or battery-related conditions.
This status signal is particularly useful in security and fire alarm systems where battery charging integrity must be monitored separately from the main DC output.
Relay Contact Alarm Outputs
The DRS-480 Series provides four Form-C relay monitoring outputs:
- AC Fail
- DC OK
- Battery Low / Abnormal / Disconnected
- Charger Fail
An external voltage source is required for the alarm circuit. The datasheet specifies a maximum applied voltage of 30VDC and a maximum current of 1A.
These relay outputs allow the DRS-480 Series to interface directly with alarm panels, controllers and central monitoring systems without requiring the monitoring device to rely solely on MODBus or CANBus communication data.
Terminal Assignment and System Connection
The DRS-480 Series provides dedicated terminals for AC input, main DC output, battery connection, alarm monitoring and communication.
The main system connections include:
- TB1: FG, AC/L and AC/N for AC input
- TB3: +V / -V for the main DC load output
- TB2: BAT. + / BAT. – for the external backup battery
- TB4: AC Fail, Charger Fail, DC OK and Battery Low / Abnormal / Disconnected Form-C relay contacts
- RJ45 communication port for MODBus or CANBus communication depending on model
- CN12 for Battery Start, temperature sensing and related control connections
For correct installation, battery wiring, alarm interface and communication wiring, engineers should follow the terminal assignment and suggested application diagrams provided in the DRS-480 datasheet.
DIN Rail Installation
The DRS-480 Series is designed for installation on TS35/7.5 or TS35/15 DIN rail. Its 110 × 125.2 × 150.7 mm enclosure is suitable for integration into security panels, fire alarm enclosures, control cabinets and other industrial electrical installations.
The unit uses free-air convection cooling. For continuous full-power operation, the datasheet recommends approximately 40mm clearance above, 20mm below and 5mm on the left and right sides. If an adjacent device is a heat source, 15cm clearance is recommended.
Need wiring and installation details for the DRS-480 Series? Review the connection diagram, terminal assignment and mechanical drawing below, or refer to the official DRS-480 datasheet for complete battery wiring, alarm outputs, MODBus or CANBus communication interface and DIN rail installation information.