completely new to modbus: how does the modbus connection work via LAN cable RJ 45 without any adapter ?

[typxxi]

I have no clue and therefore a lot of guesswork, but I have 8 growatt inverter of different types and sizes like MiC 600 - 2000 - 3000 and Min 4600 and SPH 4600 and SPH 6000.

I would like to change settings from HA or automatically like setting active power ratio or charging points / times

But for now I want to start with the basic configuration like

• a Growatt SPH 4600 with a 48 V battery
• an eastron 3 phase smartmeter and
• HA on pi 4 / soon Pi 5 running HA OS with mqtt
• GROTT Addon and GROTT integration to get the data inside HA.

I know about modbus nothing except it is only a 1:1 connection and needs a kind of master slave configuration that each devices knows who is playing which role.

And right know I am struggling about how to start: Should I setup and cut a RJ45 cable, I mean cut of the plug to connect that to the eastron which comes with terminals for each wire ?

Or can I use my LAN network for the connection ?
Can I connect the eastron with a short cable to my router and then the last meter from my switch to the Growatt inverter ?

That would be far easier, but do I need adapters for that ?

I want to avoid to cut 35 m LAN cable to get rid of the connector .

Sorry, but this is my starting point and the only other thing I know is that I need to intercept the modbus data with a proxy to add additional devices (by repeating the same signals again for these devices) that should benefit from the modbus data.

I hope someone has an idea how to get it done right.
My only proxy experience is the grott proxy server for growatt inverters to have access to the data.
In the long run I want to change settings in the growatt inverters automatically like limitin active power ratio to 20% on all inverters.

And of cause I need the modbus data for surplus charging of the EV and powering the heatpump in 2nd priority, another modbus challenge I guess cause the Wallbox Pulsar Plus is another modbus device.

THANKS A LOT

[HotNoob]

there is a lot here :P

to start, write support isn't implemented yet, because it is risky.
not hard to add, but you have to be 100% certain that you have the right protocol, because there is no good way to verify you are writting to the right spot :P

i can see about adding it, but i need to think more about what safety mechanisms to put in place.

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So, to my understanding, modbus over lan requires a server / specialized hardware. there aren't any lights on the rs485 port, so i think we can assume it's not built in.

The easiest way to get started would be to look for the USB ports, which do the hardwork of making a cable for you.

In your case, the Growatt MiC 600, should have a USB-A port. usb-a to usb-a cables are a bit rare, but available online.

For your SPH model ones, i don't see a USB port on them, so you'll have to interface either via the "Serial Port" or rs485. The manual is advertising using a standard db9 usb serial adapter. the manual mentions dip switches for the port "Before use RS232 communication, you should make sure the follow PIN1 and PIN2 are OFF" i think those dip switches control power over serial which is not standard; so make sure they are off.

as for interfacing via RS485, you'll need to find the pinout of the port, a RS485 usb adapter, and a ethernet cable. the minimum for rs485 is 2 wires. one positive, one negative. tx+, tx-. optionally a 3rd ground wire.
cut one end of the ethernet cable off and attach the appropriate wires to the usb adapter.
theese guys like to multi-purpose the rs485 ports, so they also run a can bus on some of them which can cause problems :P
for your sph inverters it's likely to to be pin 1 tx+ and 2 tx- , orange / white ( rj45 T-565B ).

oh the RS485 port may also be running a different modbus "protocol", based on the inverter's settings. it's the most difficult to connect to. i should mention it could be a lot of headache. i personally haven't connected to it yet. i've tested a bit on a sok battery but i'm getting random giberish, i think the can bus is leaking over to the modbus lines :/ and/or the documented wiring is wrong. tbf i never got modbus running between batteries/inverter, just can bus. so waiting for another rs485 adapter to verify its not the adapter.

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if you want to connect things up via ethernet to a network you'll need a modbus to lan server / adapter and i'd need to add that option in to the code to use modbus over tcp. takes 5 minutes. a usb server and/or serial server should theoretically also work if you interface that way.

i'd say start off small, take a usff pc or laptop or whatever device, install linux on it and try getting one inverter connected.

for my current setup, i'm running proxmox on a thinclient ( basically a usff ), and from there i have various vms, that way it's multi-purpose and easy to backup. bare-metal backups suck.

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the goal of this project is to be multi-purpose, so if you have the documentation for whatever device running modbus , can just whip up a csv for the most part and good to go :)

[HotNoob]

oh, and i am also relatively new to modbus stuff. but ive got a good 20+ yrs of programming experience.
it's an adventure for both of us.

[typxxi]

well,
I have not read everything cause it is quite late here and I will spend more time reading carefully.

#1
I had asked in general if there is a possibility to write back / change things inside the inverter and in particular the most important topic - also by others asked - is the whole stuff about charging during off peaking hours usually in the night especially during winter and when the surplus energy for tomorros is close to zero.

#2
I know that there are modbus based solutions that should work but I have not checked that out deeper cause I am just at the beginning only being aware that modbus is high water cause it is a 1:1 communication and I had thought to listen to that cause I had heard or read about modbus proxies even unter HA as addon .
I know that the smartmeter - hybrid connection would be the only modbus connection between both of these, but I also need that data for surplus charging of the car.

And evcc is a software capable of doing this or at least I have heard that people got it running. Right now they have not implemented this kind of off peak season charging but it is on their roadmap.

I have asked you about that cause I had thought that you would have experience on this topic if you start such a project from scratch but i guess you had simply thought that it should be possible and went your way.

Anyhow, I guess you might wanna look here for evcc even though it is a german project here is an english introduction and a bit more.
They are dedicated to work on manufacturer independent solutions to make the most out of charging the EV or EVs and surplus power consumption like heatpump or other loads that can be used or started later like sockets for dryer or dish washer and so on.

And therefore they are deep into EV chargers, smartmeters and inverters to raise the surplus usage to a new level and beyond manufacturer fences and systems. And the last step is now the idea to expand their system to integrate the local energy storage / battery into the overall picture. And the charger mess is fully a modbus story afaik, not much else, same for the smartmeter and inverters and maybe they can help you out in case of questions.

I have not asked there cause growatt is a rather small niche in their world and therefore I had asked you cause it looked for me like a perfect match for what I might need.

Again, I need to read your lines carefully on saturday or sunday or maybe friday , but i guess that it will work out sooner or later.
At least I have a fleet of different inverters and can test a lot of things out, MIN and MIC are mounted on a 3 m long wood board and the sph is 15 m away but same building.

thanks a lot for your quick reply

UPDATE: i had missed to post the evcc english link which I have now added

[HotNoob]

hmm, evcc looks like a very large and specialized project.

https://docs.evcc.io/en/docs/reference/modbus/
acording to their docs, you should be able to add unsupported devices via modbus:
If the Modbus device is not directly supported or if values deviating from the predefined models are to be read or written, the Modbus registers can also be configured manually. For this purpose, in addition to the general 'modbus' settings (see above), a registers must be defined instead of a value, as with predefined devices. It is not allowed to specify both value and register.

that's about as deep as i'll go in their documentation :P

the general hardware setup / connections will be pretty much the same for either evcc or InverterModBusToMQTT

as to the exact details; no idea.

InverterModBusToMQTT just pushes the modbus data via mqtt, then you can do whatever you want using mqtt.
more of a "back end" product where evcc is more of a "front end" product like home assistant.

depends what you want todo; how much customization ect...
InverterModBusToMQTT will be void of any logic, the goal is to be a gateway.

[HotNoob]

modbus tcp/udp/tls added if you end up going that route. untested, but should work. currently in v1.0.8 branch. will be in main when v1.0.8 is released.

e21ce64

key settings:
`[reader]
#[serial] / reader settings
#name is deprecated. new name is [reader]. contians protocol reader settings.
#if tcp/tls/udp port is the port number
port = {{serial port, likely /dev/ttyUSB0}}
baudrate = 9600

#tcp/tls/udp example
#host = 192.168.0.7
#port = 502
#override protocol reader
#reader = modbus_tcp`

[typxxi]

I will need 2 waveshare RS485 RJ45 adapters for the smartmeter and for the inverter, most likely not for the wallbox which should run natively modbus tcp via rj 45 and WLAN, but not sure .

I will start with 2 of these , also got 4 wireless adapters for direct transmission cause I have found a solution on aliexpress which offers a 1 to many modbus connection via 868 Mhz. Those are quite cheap: 4 for 35€ or so here on AliExpress
I have seen one using these devices to connect a Wallbox Pulsar Plus with an Eastron SDM630 modbus V3 .

I simply have to wait for the parts and then start with one of these.
Thanks a lot - maybe you have further ideas with these wireless lan adapters.

[HotNoob]

hmm. wireless adapters look interesting. i'd expect them to work as if wired.

waveshare seems to be a common option. expensive for me to get :P

oh. modbus signals can supposedly go 4000feet or something... so could wire them all centrally
if you have a bunch in one spot, a rs485/modbus hub could be an option... or attempt daisy chaining...

more difficult than a bunch of modbus to tcp servers or over wifi tho.

or your solution could be a combination of all of the above.