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David Molyneux avatar image
David Molyneux asked

Impact on ESS discharge from AC-in when ET112 is not found

I have an MP2GX, after the consumer unit, using AC in only. There is no solar PV, and it is simply being used for ESS battery storage and self consumption (charging from mains overnight):

  • The ET112 is connected to the USB socket on the MP2GX but it is not detected in meters.
  • The green power light on the ET112 is on but it is not flashing (indicating no comms).
  • The USB plug initially flashes red and a couple of green flashes and then stays solid red.
  • There are no extensions to the cable, it is the standard Victron cable
  • I have tried connecting with and without ferrules and have tried shortening the length of he cable and neither has made a difference i.e. I am sure the connection is good, with orange, yellow, black to terminals 4/5/6 respectively.
  • I have also tried connecting the ET112 to the laptop and using the CG software but the ET112 is not detected there either.
  • I have noticed that the USB plug on the cable gets very hot (not sure if this is normal or not for this cable).

My working assumption for now is that I either have a faulty meter or a faulty cable and will need to investigate further. What I want to understand is the impact this might have on ESS functionality if no meter is detected within the MP2GX. At the moment my batteries will charge but they will not discharge. From the ESS manual (4.3.2), it states that I must have an external meter to avoid having to connect loads to AC-out (I am just using the AC-in bidirectional). All other ESS and Pylontech settings have been entered correctly in VEConfigure and remote config of MP2GX.


Questions:

  1. My assumption is that the batteries will not discharge because the ET112 is not detected and there are no loads are present on the AC outs - is this assumption correct?
  2. The manual is not clear whether the required external "meter" to discharge via AC-in can just be a CT clamp, rather than the ET112. Can I use a CT with ESS and then charge/discharge with AC-in only?

Sorry for long post but I am just looking for options to track back the problem i.e. is the fact the meter is not found the likely reason why the batteries would not discharge and, if so, I might first try a CT (cheapest if viable), then try a new USB to RS485 cable, then try a new ET112 etc. Thanks in advance for any help.

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2 Answers
David Molyneux avatar image
David Molyneux answered ·

The usb to rs485 cable was at fault. When I removed the plastic housing there was a scorch mark inside, probably from the heat it was generating, so must have been a short:

pxl-20230221-165219282.jpg

Rather than go for the Victron one again, I decided to replace it with this item from Amazon (£18 ish) and I just reused the cable - worked first time:


pxl-20230222-174535221.jpg

There are a couple of versions so make sure to get this one with the correct chipsets:

Amazon link to USB to RS485


After I fitted this the meter started communicating within about a minute (flashing light on left) and was picked up in the meter settings. Only then I realised that they installers placed it after the consumer unit, so I couldn't use it as a grid meter and instead have used it as an AC meter. So then I needed to add an external CT clamp before the consumer unit, and set the ESS back to internal, at which point everything has come to life and is working as expected. Again rather than pay silly money for what is marked as a Victron clamp, I bought a matching item for a quarter of the price, which works just fine:

Link to CT clamp on Amazon


So the root of the ET112 meter problem was the damaged cable. I'm not yet clear if the ESS instructions are wrong and that a CT clamp can be used alone, without an ET112, for bi-directional flow on AC1 because I can't remove the ET112 from the system. It's possible it does work but for my purposes it doesn't matter now, as everything is working, hurrah! Thanks for the responses.


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sharpener avatar image sharpener commented ·


Glad you got it sorted @David Molyneux .

<Again rather than pay silly money for what is marked as a Victron clamp, I bought a matching item for a quarter of the price, which works just fine:

Link to CT clamp on Amazon>

Yes, if they are going to charge inflated prices the stuff ought to be faultless, but the leads seem to be a weak point. I had a dongle which didn't work, got a refund and realised I could do all the programming via VRM anyway so in a way it was a blessing in disguise.

<So the root of the ET112 meter problem was the damaged cable. I'm not yet clear if the ESS instructions are wrong and that a CT clamp can be used alone, without an ET112, for bi-directional flow on AC1 because I can't remove the ET112 from the system.>

Not on AC1 (Out), because the external CT takes the place of the internal one which is on the AC-In.


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sharpener answered ·

USB plug should not get "very hot". IIRC the red light on ET112 should flash once per Wh whether the interface is working or not.

CT clamp between grid and load connection point (i.e. on meter tails) should work fine. See also this thread.

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David Molyneux avatar image David Molyneux commented ·

Thanks, the ET112 does appear to be running (greeen lights on left, red flashed on right), just there are no comms (green light does not flash). I have a double 13 amp socket connected to AC1-Out, so I was able to do a test, setting the meter to internal/inverter (i.e. as it would be with a CT clamp) and the batteries do then discharge to that socket when it's in use. This would indicate that the ESS instruction is valid and the CT will not be suitable for my setup (bi-drectional using only the AC-in).


I decided to cut open the Victron USB RS485 plastic housing around the USB plug and inside there is a black mark near the solder points, which does appear to be some kind of scorch mark. I am hoping on that basis that it is the cable at fault, so I have ordered a few different types of USB to RS485, all with the same chipsets as on the Victron cable, to see if any of these will work and pick up the ET112 in the settings. If they don't work then I'll replace the ET112.

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