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April 11, 2026 11:51 pm
I have an EG4 12000XP off-grid inverter, it's currently equipped with the wifi dongle, but I want to remove that and switch to local monitoring. I'm wanting to try to do that myself versus buying the etherent dongle.
I'm trying to figure out how to get local monitoring via RS485, but I'm running into a port conflict and need help confirming the green terminal block pinout.
My comm board does NOT have the two upper RJ45 ports (CT1/CT2) that most guides reference for RS 485. My board only has BAT COM and Parallel.
My batteries are currently connected to the inverter via the BAT COM RJ45 port for closed-loop comms, so that port is occupied.
<div class="bbImageWrapper js-lbImage" title="1775951026041.png" data-src=" removed link " data-type="image" data-lb-sidebar-href="" data-lb-caption-extra-html="" data-single-image="1" data-fancybox="lb-post-1793427" data-caption="<h4>1775951026041.png</h4><p><a href="https://diysolarforum.com/threads/eg4-12000xp-rs485-terminals.123716/#post-1793427" class="js-lightboxCloser">yam404 · Apr 11, 2026 at 4:44 PM</a></p>">
What I do have is the green terminal block above.
My questions:
1. Are COM1 and COM2 on the green terminal block the RS485 A+ and B− lines?
2. If so, which is A+ and which is B−?
3. Is there any conflict with the batteries already using BAT COM, or are these completely separate?
Goal is to connect a USB RS485 adapter to the terminal block and read inverter data locally via Modbus.
April 13, 2026 9:16 pm
My 2 cents. I don't know if the 12000XP supports monitoring through RS485. I do have a 18KPV and it does have a terminal block that has RS485 on it -
See connections g. Note that connections (CT1/CT2) that you talk about are typically reserved for external current transformers. Also in your case COM1 and COM2 are relay connections to start a generator and not RS485. I'm thinking that in the case of the 12000XP. The only RS485 is through the battery connection and the WiFi dongle. I believe in my case, the RS485 is shared with the WiFi dongle connection where as the battery connection is separate (but I would need to measure it. You may be able to use the WiFi connection and make either a break out cable with a HDMI connector on it or you could follow that connection back to the board that it connects to internally. In my case, I'm connecting the RS485 to a RS485 to Ethernet adapter like this -
I then set it up for Modbus communications and use Home assistant EG4 inverter Modbus for communications.
I'm not sure what is communicated through the 12000XP dongles RS485 port but you could try it.
I did look some more and see the following -
- Port Location: Most users connect to the RJ45 port (often labeled for the Wi-Fi dongle or CT1/CT2) inside the inverter's wiring compartment.
- Pin Configuration: For custom cables, the standard pinout for RS485 communication on this unit is typically Pin 7 (RS485B) and Pin 8 (RS485A).
With a DVM, my RS485 signals measure +2.5V to ground. Of course this has the digital signal on it. The dongles cable inside my unit has 4 wires, of which the black and white wires appear to have the RS485 signals on them. Have not confirmed which is A or B on dongle cable. You could start by measuring the CT1/CT2 terminals and see if they are close to +2.5V. If you have a scope, you could also look for activity on the terminals.
