M3-40 DUAL
The Solax M3-40 Dual is a three-phase dual-channel smart meter rated at 40 A, with 2 sets of 100A/40mA CTs included (6 CTs in total). It simultaneously measures two generation devices: ideal for Solax storage retrofits on existing PV systems from other brands, dual Solax inverters, or dual PODs. 50 ms refresh rate, RS485 Modbus RTU, plug-and-play CTs, remote configuration via SolaxCloud APP, automatic phase and CT direction correction.
The Solax M3-40 Dual is a three-phase dual-channel smart meter rated at 40 A, designed for advanced energy monitoring in three-phase photovoltaic systems with storage. The unique feature of the Dual version is its ability to simultaneously measure two generation devices via two independent sets of CTs (supplied: 2 sets of 100 A / 40 mA, for a total of 6 CTs): one channel for the Solax inverter, and a second channel that can measure a third-party inverter, a second Solax inverter, or a second grid exchange point.
When should you choose the M3-40 Dual?
The dual measurement channel of the M3-40 Dual is the key feature of this product. It is the right choice in three typical scenarios:
- Solax storage retrofit on an existing PV system of another brand: the first channel measures the Solax hybrid inverter, the second channel measures the on-grid inverter of the existing PV system. This way, the Solax system knows exactly how much the other inverter is producing and optimizes self-consumption.
- Systems with two Solax inverters in parallel, where combined export control is needed.
- Systems with two separate grid exchange points (dual POD or dual meter configurations).
If the system has only one inverter and a single measurement point, the M3-40 standard model (more economical) or the Chint DTSU666 DIN-rail meter is recommended.
M3-40 Dual Technical Specifications
| Product code | SOL-M3-40-DUAL / PVI6M340DU |
| Type | Three-phase smart meter, dual measurement channel |
| Network type | 3P3W / 3P4W (three-phase with or without neutral) |
| Voltage range | 220 - 415 V AC (40 - 400 V on single phase) |
| CTs included | 2 sets of 3 CTs, 100 A / 40 mA (total 6 CTs) |
| Compatible CTs (expansion) | 100 / 200 / 400 / 600 / 1000 / 1500 / 2000 A / 40 mA |
| Refresh rate | 50 ms (high sampling speed) |
| Communication | RS485 Modbus RTU (2 ports: A/A2, B/B2) |
| Wireless transmission | Compatible with Wi-BR (up to 200 m horizontal / 20 m vertical) |
| CT connection | Plug-and-play (single terminal for 3 CTs) |
| Auto-correction | Automatic phase sequence and CT direction detection |
| Remote configuration | SolaxCloud APP |
| Safety | Electrical isolation between strong and weak current circuits |
| Display | Integrated LCD |
| Dimensions | 65 × 72 × 100 mm |
| Weight | ~500 g |
| Warranty | 24 months |
Compatible Solax Inverters
The M3-40 Dual is compatible with almost all new generation Solax inverters. The communication ports and pinout vary depending on the series:
- Single-phase inverters: X1-MINI G4, X1-BOOST G4, X1-SMART G2 (in single-phase configuration, connect only to L1 and N)
- Three-phase hybrid inverters: X3-HYB G4, X3-HYB G4 PRO, X3-IES, X3-AELIO
- Three-phase retrofit inverters: X3-FIT G4
- Three-phase commercial inverters: X3-MEGA G2, X3-FORTH
For correct RS485 pin connection, refer to the meter’s Quick Installation Guide, which provides pin-out tables for each series.
Main Features
- Independent dual measurement channel: two sets of CTs, two circuits monitored separately, data provided in real time to the Solax inverter
- 50 ms refresh rate: very fast response time, essential for precise export control and managing load transients
- Plug-and-play CTs: the single terminal for 3 CTs drastically reduces wiring time and the risk of connection errors
- Intelligent phase and CT direction adaptation: the meter automatically detects phase sequence or CT direction errors and self-corrects — greatly reducing the need for site revisits
- Remote configuration via SolaxCloud APP: change parameters without being physically on site
- Compatibility with third-party inverters: the second channel can measure a non-Solax on-grid inverter (use case: "storage retrofit on existing PV")
Typical Use Cases
- Adding an X3-Hybrid G4 to an existing PV system of another brand: the M3-40 Dual measures both the flow to/from the grid and the production of the other inverter, allowing the X3-Hybrid to calculate real self-consumption and optimize the battery
- Dual Solax inverters in parallel: two X3-FIT G4 units to cover higher power, with a single meter managing both
- Commercial installations where it is necessary to separately measure two branches of the internal electrical network
- Energy communities with dual exchange points
Frequently Asked Questions
What is the difference between M3-40 and M3-40 Dual?
The M3-40 standard is a three-phase meter with a single channel: it measures only one point (typically the grid exchange). The M3-40 Dual has two independent channels with two sets of CTs: in addition to the grid, it also measures a second device (an inverter of another brand, a second Solax inverter, a second POD). The most common use case is Solax storage retrofit on an existing PV system of another brand: the Dual allows the Solax system to "see" the old inverter as well.
Can I use the M3-40 Dual with an inverter of a different brand than Solax?
The M3-40 Dual communicates via RS485 Modbus RTU with a Solax inverter (the inverter is the "master" of the meter). However, the second measurement channel can be used to monitor the production of an inverter of another brand: the meter will clip the CTs of the second set onto the AC outputs of the old inverter, and the data will be passed to the Solax inverter via Modbus. This is exactly the storage retrofit case: you keep the old PV, add a Solax X3-Hybrid with storage, and the M3-40 Dual acts as a measurement bridge between the two.
Are CTs included in the package?
Yes. The package includes 2 sets of 100 A / 40 mA CTs (total 6 CTs, 3 per channel), already pre-wired with plug-and-play terminals. For systems with higher currents, CTs of 200, 400, 600, 1000, 1500, and 2000 A / 40 mA are available as accessories, to be paired with the meter while maintaining the same transformation ratio.
Is the M3-40 Dual required to activate export control?
To activate export control on Solax systems, you need a compatible meter: the M3-40 Dual is the right choice when the system has two generation devices to monitor. If the system has only one Solax inverter, a standard M3-40 or a Chint DTSU666 DIN-rail meter is sufficient. For commercial systems with many inverters, export control is managed by the DataHub1000 paired with a compatible meter.
Can I configure the meter remotely?
Yes. Through the SolaxCloud APP you can configure the meter parameters remotely, without needing to be physically on site. In addition, the meter has automatic self-correction functions for phase sequence and CT direction, which drastically reduce the need for corrective interventions after installation: once wired, the meter analyzes the data it receives and reconfigures itself if it detects a reversal.
What cable is needed for communication with the inverter?
Shielded twisted pair RS485 cable (recommended 0.5-1 mm² with shielding) or RJ45 Cat 5e cable depending on the communication port of the Solax inverter — the meter’s Quick Installation Guide provides a pin-out table for each inverter series. Alternatively, the meter is compatible with the Solax Wi-BR module which allows wireless connection up to 200 m horizontally.
