I’m looking for a good, quick source for a for ready-to-use modbus cable to connect a Solark15k inverter RS485 to a USR-TCP232-410S modbus TCP converter which has a terminal bloc that just takes the two power wires and a ground. I can only seem to find ones with a USB end. Would this DMX cable work or please let me know what you’ve been able to get that works: RJ45 Female to Bare Wire DMX Control Cable - Ecolocity LED
I don’t have access to any crimping tools, so something plug-and-play is highly desirable. Many thanks in advance!
Looks like I’ll have to build my own, I guess out of a pass-through CAT6 RS484 RJ45 cable and cut off one of the ends and figure out the wiring to the terminal block, which is pretty well documented in various places.
OK, got it working. Took a standard passthrough RS485 cable and cut off one end. Pin 7 (brown/white stripe) goes to terminal A on modbus device, pin 8 (brown) to terminal B , and pin 6 (green) to Ground. Restarted HA and it all came alive. There are some drop outs which might be from insufficient shielding or lack of 120 ohm termination or who knows what, but it’s mostly sending data and HA is picking it up properly. Attached is the RS485 configuration on the modbus unit.
I did not have to do anything on the Solark end other than plug in the RJ45 cable to the modbus port. The Solark in question is the model 15k-2P-N, so there may be variations for other inverters. Check the Solark manual for details. Purportedly, the Battery CANbus port can also be used, as the battery uses different pins.
P.S. Have not seen any logged errors since Dec. 29. Occasionally, the display shows “unavailable” but it seems to correct itself presently. Hard to tell from the graphs if there are actual small gaps or it’s just their limited resolution. The huge gaps from earlier no longer seem to be showing up, which is encouraging.
Gaps now showing up primarily at night. More research needed …
Tried foil shielding with little to no effect. May have to try a better shielded cable at a future date and.or changing modbus parameters. Anyone have any suggestions for the modbus settings?
I may have found a good quality, well-shielded cable but it will be a long time (months?) before I can test it out. Will likely post eventually if it works so others can benefit.
Yay… I found a great quality cable at l-com.com:
Category 5e Cat5e Cable Assembly, SF/UTP Double Shielded, 26AWG Stranded, RJ45 Male Plug to RJ45 Male Plug, LSZH Jacket, Gray, 12F
SKU: TMD03014014002-012F
The modpoll program is now working with no evident timeouts so far today. Here’s the configuration that seems the best for the RS485 to a USR-TCP232-410S modbus TCP converter:
I hope this puts the issue finally to rest.
The bottom line: Use a good quality, well-shielded cable!
Note added 4/03/2026: Still timing out, sadly, even though everything looks stable. and sometimes requiring a restart.
Why is it still timing out? Am at a loss what else to do. Try the Canbus/modbus dual port instead? Get a different model RS485-Ethernet converter? Does anyone use any of the polling or heartbeat options?
It looks as if you have solved many of your issues, however Modbus always seems to have an unnerving ability to surprise even when you think you have everything correct.
I have a Solis inverter, and connect via RS485 Modbus using the USR LipStick adapter (replacement for the TCP232-410S I used to use). I run a Node-RED flow that polls the inverter every 15 seconds to read registers directly.
For the RS485 wiring, any twisted pair cable will do. RS485 is quite robust, and although the specifications require terminating and pull up resistors, for short runs they seem to be irrelevant. I just use an old Ethernet patch cable with one end cut off to connect to the adapter terminal block. I used 120 ohm terminators at first, but have not bothered when I switched to the new adapter. Many inverters, and some adapters, have them as standard anyway.
If you have shielded cable (I don’t) then the shielding must be connected to one ground and not both. Ground should not be connected between inverter and adapter or used for anything else either.
Your adapter settings look OK. I have always been suspicious of the Sync Baudrate (RF2217) option, wondering if it confuses a simple inverter, but I seem to have it set on and without causing any issue.
I have the [equivalent settings for] TCP Server MAX Sockets set to 4, and Up to MAX as “KICK” to ensure that, at restarts and resets, the adapter does not fill up with old unwanted WebSocket connections.
Communication timeouts can be caused by the inverter I suspect. At a major overhaul of my code, I moved to reading fewer and smaller blocks of registers, and modified the polling frequency. Like you, I spent quite some time tinkering with the wiring and the adapter settings, but in the end it appears that a change in how much and how often I read the registers has finally fixed the error rate. I used to get one or two failed read every hour or so, now I get a failed read once a month (out of around 850,000 individual read requests).
Why is it still timing out? A very good question. If it works for a bit, then starts to cause issues, perhaps the adapter needs rebooting. If you start to see issues at night, then definitely the inverter is a suspect. Hybrid inverters stay awake at night to manage the battery, but I think that the internal software has a different update cycle, and may respond differently to constant Modbus read requests.
Canbus/modbus port: This is most likely for the battery control. CANbus is used commonly, with the battery sending small CANbus messages every second to the inverter. The RS485 side typically provides an alternative option for battery units that use Modbus or similar protocol over RS485 rather than CANbus. You are unlikely to get much information out of these ports as they are used for input from the battery.
Different model converter: I have switched to the Lipstick model, and have found it quite acceptable.
I don’t use either polling or heartbeat, since my own Node-RED code is fairly constantly doing the job of both, thus keeping the connection alive.
Geoff, very helpful feedback, many thanks! I DO have the ground (pin 6, green) connected to the TCP232-410S Ethernet adapter – should I pull it off? It started up again after a reload and reboot and has been running for many hours, so overnight does seem to be perhaps an issue. I will try your reducing MAX sockets to 4 (I have 8) and keep the KICK option. I tried the polling option every 15 seconds, but that didn’t seem to work/help.
I DO intend to ultimately implement Node-RED to be able to control my power options based on multiple factors, so that heartbeat may eventually help, as well.
The Sol-Ark inverter port seems pretty sensitive, alas, but this new shielded cable is definitely a big improvement. I do NOT currently have any battery associated with the Sol-Ark, so I guess the CANbus is irrelevant.
Reducing the number of entities is also a good suggestion and worth trying – I have 72 I believe currently I’m polling, way more than needed.
Many thanks again, and I’ll keep you posted as things continue. Will only be able to work with this for a few more days then have to take a hiatus for a number of months before I can continue work but will then be able to work with it for many months.
As far as I understand this stuff, on RS485 wiring, ground is optionally only used to connect one end of the cable shielding. The A-B pair connect using opto-isolators, and ground should not be wired at both ends, to ensure that there is no physical electrical connection between adapter and inverter. If you have ground connected to the spare wire(s) and it works, fine, but if you don’t know what happens at the inverter plug end of the wire, personally I would disconnect the wire (green) at the adapter, and instead connect the adapter ground to the cable shielding instead (if at all) leaving the inverter end of the shielding unconnected.
I don’t know anything about your inverter, but only hybrid inverters stay running at night, and that is only so as to manage the battery. Inverters are all supposed to get their power from the DC side, hence standard inverters wake up when the sun shines, and go to sleep at night. My Solis hybrid certainly takes power from the solar side, but at night it uses either the batteries or the mains to run. I know from experimenting that it will actually run from the grid connection at night if I disconnect the battery, but I don’t think it is normally supposed to do this.
My first guess is that, with a hybrid inverter and no connected battery to look after, the inverter is turning off or reducing workload. This would, of course, explain very well why the connection drops (and at night).
Geoff, this is extremely helpful as I was unaware of the Sol-Ark inverter’s nighttime behavior. Indeed, last night, the data shows a cut off-right at 1:00 AM and stayed intermittent until just before 6 AM this morning. However, the laptop’s time zone is 2 hours later, so the real times locally were 11 PM and 4 AM, respectively. And since, it is solid once again, that would indicate exactly what you said about the data loss at night. The day before, the cutoff went away also around 7 AM.
The RJ-45 end on the Sol-Ark has no modifications; I just have the green pin 8 wire plugged into the TCP232-410S. Nothing on that end is attached to the shielding.
Also, I’m only pulling into HA 15 of the 72 Sol-Ark entries.
Given that, should I just leave everything alone?
So, maybe, I should just leave everything alone as it appears to be behaving as expected? Again, your feedback has been really, really helpful – many thanks!
–Tobias
As I said, I don’t know your Sol-Ark inverter, however the online documentation looks much like any other inverter.
It certainly looks more like that inverter is causing the issues you are seeing, and since you can’t really do much about that (except add a battery) then just leaving everything as it is makes good sense!
Perhaps sometime you can compare notes with someone who has a Sol-Ark, with the same HA integration, but has a battery connected. I would expect the inverter to respond throughout the night, just as my Solis Hybrid does.
Agreed, and also, there’s a Meta/Facebook Sol-Ark forum I might try checking out for people who may have direct experience with this inverter.
Many thanks again for all your valuable feedback, Geoff!