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RS485 Communication ports testing
Table of Contents
- Introduction
- RS485 Overview
- General RS485 Troubleshooting Steps
- RS485 – 4 PIN COM port – 5G+4G Series
- RS485 – USB COM port – S6 Series
- RS485 – S6 Hybrid Series (RJ45)
- RS485 – Solis S5-GC(50-60)K (16-pin COM port)
- RS485 – Solis Large PV Grid Inverters
Introduction
RS485 is a widely used communication protocol in Solis inverters for data exchange with monitoring platforms, energy meters, and other BMS components. Ensuring proper RS485 functionality is essential for reliable system operation. This guide provides detailed troubleshooting steps for various RS485 port types used across Solis inverter models.
RS485 Overview
Purpose: Communication between inverters and:
- SolisCloud modules (WiFi/LAN/GPRS)
- Third-party platforms
- Meters/BMS
Common Issues:
- No data reaching monitoring platforms
- Unstable communication
- Fluctuating communication status in monitoring platforms
General Troubleshooting steps
✅ 1. Visual Inspection
- Ensure that the connector is properly inserted and secured.
- Check for any physical damage to the connector or cable.
- Look for burn marks or corrosion on the port.
✅ 2. Interference and Grounding
- Shielded Cables: Use shielded twisted-pair cables to minimize electromagnetic interference.
- Proper Grounding: Ensure all devices share a common ground reference to prevent ground loops.
✅ 3. Cable and Connection Testing
- Use a LAN cable tester or multimeter to verify continuity from one end of the cable to the other.
- Ensure the correct wiring between devices (miswiring can prevent communication).
✅ 4. Firmware and Software Checks
- Firmware Updates: Verify that the inverter and connected devices have the latest firmware versions.
- Monitoring Software: Ensure compatibility and proper configuration of monitoring software or platforms.
✅ 5. Swap Devices
- Swap inverter or communication device to isolate fault.
RS485 Troubleshooting
4 PIN COM port – 5G+4G Series
This port is a green port located externally on all Solis inverters on the bottom of the inverter.
When plugging the connector to this port, please make sure that it is plugged correctly.
On the connector you will see a “ridge”. Make sure that this aligned with the groove on the plug.
When troubleshooting this connection please consider the following
Pin 1 = +5 volts DC
Pin 2 = -5 volts DC
Pin 3= +RS485
Pin 4 = -RS485
Checking the voltage on pins 1 and 2 with a multimeter will ensure power is provided to the communication device (ex: wifi datalogger. The voltage reading should be 5V on DC.
Checking the voltage on pins 3 and 4 with a multimeter will ensure RS485 signal between the inverter and the communication device. RS-485 voltage should read ~1.7Volts on DC
USB COM port pinout for dataloggers – S6 Series
Pins 4 PIN port vs USB Port
Therefore when troubleshooting the USB connection please consider the following
Pin 1 = +5 volts DC
Pin 2 = RS485A
Pin 3 = RS485B
Pin 4 = GND
Checking the voltage on pins 1 and 2 with a multimeter will ensure power is provided to the communication device (ex: wifi datalogger. The voltage reading should be 5V on DC.
Checking the voltage on pins 3 and 4 with a multimeter will ensure RS485 signal between the inverter and the communication device. RS-485 voltage should read ~1.7Volts on DC.
RS485 Communication Troubleshooting – S6 Hybrid Series (RJ45)
The RS485 communication interface is essential for monitoring and controlling Solis inverters through external devices such as data loggers or monitoring platforms. The S6 Hybrid Series utilizes an RJ45 connector for RS485 communication, but port location and pin assignment vary between models.
RS485 Port Location
The RS485 port may be located in different areas, depending on the inverter model:
- S6-EH3P(5-10)K-H-EU: All communication ports are located below the cover.
- S6-EH3P(12-20)K-H: Communication ports are found behind the front cover.
Always refer to the user manual of the specific inverter model for the exact location of the RS485 port.
There are 2 types of RJ45 Pin Assignment Examples
- Example 1: RS485 via Pin 4 (A+) and Pin 5 (B-)
- Example 2: RS485 via Pin 1 (A+) and Pin 2 (B-)
Pin assignment may vary. Always consult the model-specific installation manual.
Troubleshooting Checklist – RS485 Communication Issues
If the RS485 communication link is not working (e.g., inverter not communicating with the external device), follow this systematic troubleshooting guide:
✅ 1. Voltage Level Check
Measure the DC voltage between the RS485 A and B lines using a multimeter:
• Expected differential voltage: Typically between 1V and 5V DC when the bus is idle.
• A reading of 0V could indicate:
o No power to the RS485 transmitter
o Broken or miswired cable
✅ 2. Baud Rate & Protocol Settings
• Confirm that both the inverter and the connected device are configured with:
o The same baud rate (typically 9600 bps)
o Matching parity, stop bits, and address
• Incorrect settings can prevent communication even if the wiring is correct
✅ 3. Cable Length & Network Topology
• Keep RS485 wiring as short as possible to minimize signal degradation.
• Long or improperly terminated lines are a common cause of intermittent communication issues.
✅ 4. Wiring Practice & Short Circuits
• One of the most common RS485 faults is a shorted or miswired line.
• When using LAN (Ethernet) cables, a practical and reliable method is:
o Use all white wires (e.g., white-orange, white-blue, etc.) for RS485 A
o Use all colored wires (e.g., orange, blue, etc.) for RS485 B
• This approach reduces mistakes and improves signal consistency across the line.
RS485 Communication Troubleshooting – Solis S5-GC(50-60)K - 16-pin COM port
The Solis S5-GC(50-60)K inverters utilize a 16-pin COM port for RS485 communication, facilitating connections with meters, data loggers, and other monitoring devices. Proper RS485 communication is crucial for system performance and monitoring.
16-Pin COM Port Overview
The 16-pin COM port supports multiple communication channels:
- Pins 1 & 2: Meter RS485 (A & B)
- Pins 3 & 4: COM1 RS485 IN (A & B)
- Pins 6 & 7: COM2 RS485 OUT (A & B)
- Pins 15 & 16: 12V Power Supply (V+ & GND)
For daisy-chaining multiple inverters:
- RS485 IN: Pins 3 (A+) & 4 (B-)
- RS485 OUT: Pins 6 (A+) & 7 (B-)
Refer to the Solis S5-GC(50-60)K Installation Manual for detailed diagrams and configurations.
Troubleshooting RS485 Communication Issues
If communication failures occur (e.g., inverter not detected by monitoring devices), follow this step-by-step guide:
✅ 1. Voltage Testing
Using a multimeter:
- Between Pins 3 & 4 (RS485 IN): Measure DC voltage; a typical idle voltage ranges from 1V to 5V.
- Between Pins 6 & 7 (RS485 OUT): Similar voltage readings indicate proper signal transmission.
If voltage exceeds 5V between pins 3 and 4, refer to the GC COM plug fix for corrective actions.
✅ 2. Device Configuration
- Baud Rate and Settings: Ensure all devices on the RS485 network share the same baud rate, parity, and stop bits.
- Device Addressing: Assign unique addresses to each device to prevent conflicts.
RS485 Communication Troubleshooting – Solis Large PV Grid Inverters (S5-GC80K, 5G PRO, 100–110K)
RS485 Connection Options
Besides the 4PIN Com Port, these inverters support two further RS485 connection methods, both of which can be used depending on installation preferences and site conditions.
1. RS485 via RJ45 Connector
Use an outdoor-rated CAT 5 STP cable
RJ45 Pin Mapping (TIA-568B Standard Colors):
Pin | Color | RS485 Function |
1 | White/Orange | RS485 A+ |
2 | Orange | RS485 B− |
4 | Blue | RS485 A+ (linked) |
5 | White/Blue | RS485 B− (linked) |
2. RS485 via Terminal Board
For more permanent or protected installations, the inverters feature a terminal board with dedicated RS485 ports:
Port No | Label | Description |
1 | RS485A1 IN | RS485 A+ (Input) |
2 | RS485B1 IN | RS485 B− (Input) |
3 | RS485A2 OUT | RS485 A+ (Output, for daisy chain) |
4 | RS485B2 OUT | RS485 B− (Output, for daisy chain) |
Troubleshooting Checklist: RS485 Communication
If you experience issues such as no data logging, inverter not detected, or signal dropouts, follow this structured diagnostic process:
✅ 1. Voltage Testing (Idle Bus)
- Measure DC voltagebetween A and B:
- Should typically read 1–5V DC when the line is idle.
- 0Vmeans:
- RS485 driver inactive
- Incorrect wiring
- Cable break
- Both RJ45 and terminal blocks should show similar values on their respective lines.
✅ 2. Protocol & Baud Rate Matching
- Confirm baud rate, parity, and stop bit settings match across all devices.
- Common baud rates
- Check Modbus address and communication protocol
