I’m looking for some help getting a stable Modbus TCP connection between my Growatt inverters and Homey Pro 2023.
System setup
46 × 420 Wp solar panels
3 × Growatt MIN inverters:
MIN 3600TL-XH
MIN 4200TL-XH
MIN 4600TL-XH
All inverters connected through an Elfin EW11 RS485-to-WiFi gateway
Unique Modbus IDs configured for each inverter
Homey Pro 2024
Using the Modbus TCP/IP app by Ronny Winkler
What works
After rebooting the EW11, everything works perfectly:
Reading registers
Writing registers
Controlling active power via Register 3 (0-100%)
The problem
After running for some time (typically within an hour), communication becomes unstable and I start receiving the following error “Connection to modbus server closed” on write and read commands
What I have already tried
Verified unique Modbus slave IDs
Checked EW11 configuration against the Growatt Modbus protocol
Placed a dedicated Wi-Fi access point very close to the EW11 to rule out Wi-Fi signal issues
Reduced the polling frequency, increased polling frequency (to keep the modbus live)
Questions
Has anyone experienced similar issues with Growatt + EW11 + Modbus TCP?
Could missing RS485 termination resistors be the cause? I don’t have the start and end resistors in place of 120 ohm. Connection between the EW11 and 3 growatts is less then 2 meters.
Are there specific EW11 settings (packing time, timeout, TCP settings, heartbeat, etc.) known to improve stability?
Is there a recommended polling interval when communicating with multiple Growatt MIN XH inverters?
Goal
My goal is to dynamically control inverter output based on hourly electricity prices:
Export when prices are positive
Run approximately zero-on-the-meter around €0/kWh
stop production when the effective export price becomes sufficiently negative
Any suggestions or experience with a similar setup would be greatly appreciated.
I don’t use the SolarEdge + Growatt Modbus TCP app, but the Modbus TCP/IP app, because with the SolarEdge + Growatt app you can only read data and cannot write data.
Is it normal to post issues directly in the topic of the app? I wasn’t aware of that, so I will do that from now on.
The app specific topics are there to combine all posts related to that app. So all questions, answers, knowledge is available in one place.
Normally the developer of the app is also the one that created the related topic. Whenever you post something in that topic, the developer (topic starter) also gets a notification of your post. This makes it easier to get a response from the developer him-/herself (when relevant).
Therefore it is recommended to first check if there is an app topic available (either in the English or your local section) of the forum.
Moderators also tend to move posts created in new topics out of the app specific topic, to the app specific topic in order to centralize the posts. You also help them by checking for an existing app topic .
1st the solaredge modbus app supports a lot also writing many registers from flow but use the test version of the app. many growatt users submitted PRs to make it better. lst year was all about Growatt.
so modbus app is maybe good for writing things once in a while . but like always make sure you don’t over do it. only 1 app can have the tcp connection and don’t do it every 10 seconds , every 30s or every 1 min is ok.
off course you can also replace the rs device and use lan which is always better than wifi. I know some have those ali express ones.
Plus when there are many read actions from many devices you can put some modbus proxy in between so inverters don’t have this load and you can do other apps at the same time.
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