Qcells Q.VOLT P5T-X (pv)
The Qcells Q.VOLT P5T-X is a three-phase string inverter for grid-tied PV systems, used in residential and light-commercial installations. Via Modbus TCP, this template reads total AC output power, cumulative energy yield, per-phase AC voltages on phases A, B, and C, and per-phase AC currents on phases A, B, and C. All registers are read-only input registers polled with function code 4. Connecting the portal to live generation data lets you verify inverter output, catch phase imbalances, and report yield accurately without relying on proprietary cloud services.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 8, read only
- Brand
- Qcells
- Compatible models
- X3-MIC G2 · X3-PRO G2 · Q.VOLT P5T-X · Q.VOLT P17T-X
- Last updated
Registers (8)
8 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read | |||
| energy | Wh | Read | |||
| currents_a | A | Read | |||
| currents_b | A | Read | |||
| currents_c | A | Read | |||
| voltages_a | V | Read | |||
| voltages_b | V | Read | |||
| voltages_c | V | Read |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor total AC output power in real time to verify the inverter is producing at expected levels.
- Track cumulative energy yield over months to report accurate generation figures to building owners.
- Compare per-phase voltages across phases A, B, and C to detect grid asymmetry or wiring faults early.
- Alert on unexpected drops in phase current to identify partial shading, string failures, or DC faults.
- Verify inverter output against utility meter readings to validate self-consumption calculations on-site.
Installation
Enable Modbus communication on the Q.VOLT P5T-X by navigating to the inverter's advanced settings menu and confirming that the Modbus baud rate is set to 19200, 8N1, with unit ID 1.
Connect the ModbusCloud Gateway to the inverter's RS485 port using a twisted-pair cable, then use an RS485-to-Ethernet adapter configured in TCP server mode on port 502 to bridge the serial bus to your LAN.
In the ModbusCloud portal, add the Gateway, import the Qcells Q.VOLT P5T-X template, and assign unit ID 1 (or the ID configured on the inverter) to the device.
Spot-check the connection by reading the power register at address 1038 during daylight hours and confirming the value matches the inverter's local display.
Things to watch for
All register values read as zero even during daylight. Why?
The inverter only populates input registers while it is actively producing power. At night or during a grid fault the device returns zero for power and current registers. Confirm the inverter display shows active output before concluding there is a Modbus problem.
Phase voltage readings look implausible. What should I check?
Voltages and currents in the SolaX/Qcells register map are scaled by a factor of 10, meaning a raw value of 2300 represents 230.0 V. Verify that your polling application or the ModbusCloud portal is applying the correct scaling factor. If the template is imported without modification, scaling is handled automatically.
The gateway cannot connect to the inverter at all. What is likely wrong?
Check RS485 polarity: the A lead of your adapter must connect to the A terminal of the inverter and B to B. Confirm the baud rate on the adapter matches the inverter setting (default 19200). A termination resistor of 120 ohms across A and B is required if the inverter is the last device on the bus.
Energy yield register shows a suspiciously large or stale value. What is happening?
The energy register (address 1059) is a uint32 cumulative counter that increments from the inverter's installation date and never resets. Very large values are normal for older installations. If the value does not increase over consecutive polls, the inverter may be in standby or the RS485 connection may be dropping packets intermittently.
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