I was able to successfully read Modbus data from the **RUiXU RX-12K** (and likely any SAJ-based clone).

Although the inverter has **two RJ45 Modbus ports**, they are **not independent buses**. Both ports are connected to the same Modbus RTU network.

The factory **USB Wi-Fi/Bluetooth dongle is the Modbus master**, so if the dongle is installed you **cannot actively poll the inverter** without risking bus collisions. However, you **can connect a USB-RS485 adapter in parallel and passively listen** to all Modbus traffic.

The downside is that the factory dongle only performs a full polling cycle about **every 5 minutes** (with some additional polling when using the ELEkeeper app), so updates are not continuous.

If you unplug the Wi-Fi dongle, your computer becomes the only Modbus master and you can poll the inverter as fast as you like (typically once per second or faster). The tradeoff is that you lose communication with the **ELEkeeper cloud/app** while the dongle is disconnected.

I've reverse-engineered enough of the register map to display:

* Battery information
* PV inputs
* Grid measurements
* Load measurements
* Energy counters
* Device information
* Various inverter settings

My next step is integrating everything into **Home Assistant** so the inverter can be monitored locally without relying on the cloud.



I think a lot of RUiXU/SAJ owners would find this useful, since there is very little public documentation on the Modbus implementation.

Here is the github link to the python script I have so far. 

[https://github.com/ch0de/Ruixu-rk-12k-saj-inverter-Modbuss-passive-listener/tree/main](https://github.com/ch0de/Ruixu-rk-12k-saj-inverter-Modbuss-passive-listener/tree/main)

RUiXU / SAJ Clone Modbus data Pulling