Qcells Q.VOLT P17T-X (pv)
The Qcells Q.VOLT P17T-X is a three-phase string inverter for commercial and residential PV installations, covering the 17 to 30 kW power range. This Modbus TCP template reads the inverter's total AC output power, cumulative energy yield, and per-phase AC voltages and currents across all three phases. With these registers polled continuously through the ModbusCloud Gateway, operators gain a clear view of generation performance and phase balance without relying on proprietary cloud portals. The template also supports the SolaX-based X3-MIC G2 and X3-PRO G2, which share the same register map.
- 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…
Send your device list
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 during daylight hours.
- Track cumulative energy yield over weeks and months to report on PV system performance against contractual targets.
- Compare per-phase currents on phases A, B, and C to detect string imbalance or wiring faults early.
- Alert on unexpected drops in AC output power during peak irradiance to identify shading, soiling, or inverter faults.
- Verify per-phase voltages remain within grid tolerance limits to confirm stable grid connection across all three phases.
Installation
Enable Modbus TCP on the Q.VOLT P17T-X by connecting the SolaX PocketWiFi 3.0 or PocketLAN dongle and activating Modbus communication in the inverter's communication settings, ensuring port 502 is used.
Connect the inverter's dongle to the same LAN segment as the ModbusCloud Gateway, either via a switch or directly to the local router, and confirm the inverter has a stable IP address.
In the ModbusCloud portal, add a new device, select the Qcells Q.VOLT P17T-X (pv) template, enter the inverter's IP address and set the Modbus unit ID (default is typically 1), then save.
Spot-check the connection by reading register 1038 (power) in the portal's live data view: a non-zero value during daylight confirms successful communication.
Things to watch for
The gateway connects but all register values are zero or absent.
Confirm that the PocketWiFi dongle firmware is version 3.0 or later, as earlier versions do not expose Modbus TCP. Also verify that the inverter is not in night or standby mode, which can suppress output registers. Check that the Modbus unit ID in the portal matches the inverter's configured slave address.
Phase voltage or current values look scaled incorrectly. What is wrong?
The X3-MIC G2 and Q.VOLT P17T-X registers for voltage and current use a scaling factor documented in the SolaX Modbus protocol: voltages are typically reported in units of 0.1 V and currents in 0.1 A. If raw integer values appear ten times too large, verify that the ModbusCloud template scaling matches the protocol specification.
The portal shows timeouts intermittently. How do I stabilize the connection?
The Modbus TCP server in the PocketWiFi dongle supports only a single simultaneous connection. If another client such as a monitoring app or home automation system is polling the inverter at the same time, the ModbusCloud Gateway will be disconnected. Disable any competing Modbus TCP clients or set a sufficiently long polling interval to avoid conflicts.
Energy yield register 1059 reads an implausibly large or static value.
Register 1059 is a uint32 spanning two consecutive 16-bit input registers and represents total lifetime yield. Ensure the Modbus master reads both registers as a single 32-bit word with big-endian byte order, as the SolaX protocol uses big-endian word order. Reading only the high or low word separately will produce incorrect results.
Want to see how it works?
