Remote consumption meter for Solis Inverter

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fastbike

212 posts

Master Geek

#319128 25-Mar-2025 11:00

I have a Solis S6 inverter, fitted with a Eastron SDM630MCT consumption meter. The meter uses 3 CTs to monitor the current and hence the power. The inverter polls the meter on a regular basis across a RS485 modbus wire to fetch numerous data points.

I want to move the meter so that it is sited at the point where the grid is connected to the property so the inverter is aware of other loads such as the car charger in a stand alone garage. There is a ethernet cable connecting the garage and house i.e. a LAN connection.

Before physically moving the meter I've tried a local replication using two RS485/ETH bridges from Waveshare in the following configuration:

Inverter (rs 485 master)
waveshare bridge set as tcp client (pointing to ip/port of the tcp server)
network switch
waveshare bridge set as tcp server
meter (rs 485 slave)

According to waveshare tech support this should work, but there's no connection. The active lights on the bridges are on, but the data is not seen by the inverter.

Any clues in getting this to work would be helpful.

Edit: direct connection of CT over this distance is not an option. Neither is using one of the TP in the Cat6 cable.

Otautahi Christchurch

neb

11294 posts

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#3357618 26-Mar-2025 21:18

That sounds a bit like something where it's more a surprise than an expectation that it works, they're not really meant to be used that way. A better option would be a wireless RS485 bridge, so the devices at both ends just see a physical RS485 connection to the other side.

fastbike

212 posts

Master Geek

#3357627 26-Mar-2025 22:39

neb:

That sounds a bit like something where it's more a surprise than an expectation that it works, they're not really meant to be used that way. A better option would be a wireless RS485 bridge, so the devices at both ends just see a physical RS485 connection to the other side.

LoL. Great advice. Not really helpful.

Otautahi Christchurch

elpenguino

3419 posts

Uber Geek

#3357704 27-Mar-2025 09:35

Have you tried swapping the client and server to the other end?

Sometimes data flow is opposite to the TCP flow.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

dasimpsonsrule

147 posts

Master Geek

#3357711 27-Mar-2025 10:20

Screenshot of the config? That should work, so long as you get the baud and parity correct. There should also be a packing delay setting, which is how it translates the RS485 to TCP, from memory on modbus rtu there should be a 1.5 character time delay to mark the end of the packet (so if you take 15 / baud would give you the delay)

fastbike

212 posts

Master Geek

#3358865 31-Mar-2025 09:53

elpenguino:

Have you tried swapping the client and server to the other end?

Sometimes data flow is opposite to the TCP flow.

Tried that no difference.

dasimpsonsrule:

Screenshot of the config? That should work, so long as you get the baud and parity correct. There should also be a packing delay setting, which is how it translates the RS485 to TCP, from memory on modbus rtu there should be a 1.5 character time delay to mark the end of the packet (so if you take 15 / baud would give you the delay)

No ability to set a packing delay on these devices.

Going to get the 'scope out and see what is happening on the serial wires.

Otautahi Christchurch

fastbike

212 posts

Master Geek

#3360968 5-Apr-2025 13:47

The scope traces showed quite a delay between the inverter sending the request and receiving the data as the Waveshare device was buffering the whole message before sending over TCP, so this happening at each end plus around 5mSec on the wire for the request and the response. Long story, short: the meter response was arriving just before the inverter was sending another request so it was failing.

As the baud rate could not be changed on the inverter, but could on the meter, the solution was to change the meter end to 38.4k which sped things up sufficiently to make it work.

Otautahi Christchurch

neb

11294 posts

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#3361056 5-Apr-2025 20:03

I've struck something similar with client requests to modbus gateways, because the latency on the TCP side is essentially zero while on the serial side it's very much nonzero you can't poll too fast on the TCP side. When you have multiple clients polling at different intervals you eventually get overlaps where multiple lengthy serial requests are in flight at the same time. Took awhile to figure that one out because it was time-dependent and things worked most of the time, and even when they didn't it wasn't an obvious failure but just slightly odd register values and things.