Monitors APC Smart-UPS On-Line SURTD-series via Modbus TCP
Overview
Modbus TCP template for APC Smart-UPS On-Line SURTD-series UPS units equipped with a Network Management Card AP9631. It reads UPS status, battery health, input and output electrical parameters, and remaining runtime. No write or control registers are included.
Key readings
Remaining Run Time
Battery Charge State
Battery Voltage and Temperature
Input Voltage
Output Voltage and Frequency
UPS Status Display
Use cases
Monitor remaining UPS runtime and battery charge state on a live cloud dashboard for remote sites.
Create an alert when battery charge drops below a critical threshold to trigger timely maintenance.
Track input voltage trends over time to identify recurring mains power quality issues.
Log battery temperature readings to detect cooling failures in server rooms or network closets.
Verify output voltage and frequency stability after UPS installation or firmware updates.
Provide facility managers with a weekly report on UPS health without requiring on-site visits.
Installation
1Install the APC Network Management Card AP9631 into the management slot of the SURTD-series UPS and connect it to the local network with an Ethernet cable.
2Assign a static IP address to the AP9631 card and enable Modbus TCP via the card's web interface or CLI, noting the TCP port (default 502).
3Connect your ModbusCloud gateway (MCG or MLP series) to the same network as the AP9631 card and ensure it can reach the card's IP address.
4Import the APC Smart-UPS On-Line SURTD template from the ModbusCloud template library into your project.
5Configure the template connection settings with the AP9631 IP address and Modbus TCP port, then verify that readings appear on the dashboard.
6Confirm that the Remaining Run Time value at address 128 is read correctly as a uint32 (two registers) and not as two separate 16-bit values.
Things to watch for
01
I see zero or incorrect values for Remaining Run Time. What is wrong?
The Remaining Run Time register at address 128 is a uint32 value that spans two consecutive 16-bit registers. Make sure your gateway is configured to read this as a single 32-bit unsigned integer rather than two separate registers.
02
The gateway cannot connect to the UPS over Modbus TCP. What should I check?
Verify that the AP9631 Network Management Card is installed and has Modbus TCP enabled. Check that the card has a valid IP address, that the gateway is on the same subnet or has a route to it, and that TCP port 502 (or your configured port) is not blocked by a firewall.
03
Do I need a specific firmware version on the AP9631 card?
Modbus TCP support requires a firmware version on the AP9631 that includes the Modbus TCP agent. Check the APC support site for the latest firmware and ensure the Modbus feature is listed as supported.
04
Can I also send commands or control the UPS with this template?
No. This template is read-only and does not include any write or control registers. It is designed solely for monitoring UPS status and electrical parameters.
Registers (10)
10 read / 0 write
Name
Address
Function
Type
Unit
Access
Remaining Run Time
128
FC03
uint32
min
R
Output Voltage
142
FC03
uint16
V
R
UPS Status Display (0-OK _>0 Error)
26
FC03
uint16
R
Battery Temperature
135
FC03
int16
°C
R
Battery Charge State
130
FC03
uint16
%
R
Utilisation Watts
136
FC03
uint16
%
R
Battery Voltage
131
FC03
uint16
VDC
R
Input Voltage
151
FC03
uint16
VAC
R
Output Frequency
144
FC03
uint16
Hz
R
Supply Drop Out
18
FC03
uint16
R
Working with Modbus in your projects?
ModbusCloud is the hardware-plus-software platform that installers use to monitor, visualise and control Modbus devices from one portal. This template is one of hundreds you can use right away.
