OpenEnergyMonitor Community

Checklist for new emonPI with solar installation

I would like to install the emonpi with the solar functionality and I would like to see how easy is it is for my particular setup.

  • Solar PV inverter/battery/meters are all in the attic of the house, above the first floor and I have one AC cable and one cat6 cable (goes to CT clamp) that go to my consumer unit on the ground floor.
  • Can I somehow connect the emonpi in the attic only? Or do I need to also use a CT clamp at the consumer unit? If yes then could I use another pair inside the same cat6 cable?
  • My network gear is in the attic also so I would have a stable LAN connection nearby.
  • I assume with this I cannot get any battery data at this time? Will the battery usage show up as grid usage on the emonpi?
  • I also have a shellyEM at my consumer unit which is CT clamped to my mains supply so I could get live values from this if it can be integrated with emonpi via mqtt for example.
  • Can the emonpi be connected to the inverter via modbus/rs485 to obtain data that way?

First, you must NEVER clamp the sort of current transformer we use, the ferrite core type, onto a cable. Doing so runs a very real risk of cracking the core, which makes the c.t. unusable.

What is that “AC cable” used for? Does it tie a secondary C.U. in the attic to the main house C.U?

Yes you do, to measure the nett grid power and its direction.

That should be OK, provided that you use the twisted pairs in the cable properly,

If you can do those things, then that should be OK.

If there’s no means of communicating with the charger (e.g. a data bus), then no.

That depends entirely on what power passes through the c.t. Viz:

  • If the c.t. is on the inverter feed, then the battery nett power will appear as house use.
  • If the P.V. feeds d.c. to the battery and both share an inverter, and the c.t. is on the cable going to the main C.U., then the nett input/output from the attic will show up as “P.V. Generation” - effectively showing battery charging from the mains as P.V. consumption.

As I pointed out to another user earlier today, unless that measures the direction of power flow, then its output is largely meaningless when you can return energy to the supply. There’s no specific statement that this is the case from what I could see, but it’s something that you should be able to verify very easily. If it can produce a meaningful output , i.e. the power and direction of power flow, and it has the ability to send the data in an appropriate format, you should be able to receive the data in the emonPi. However, I can’t advise you regarding the details, it’s not within my area of expertise.

Have you not seen the live topic about exactly that? If you have full details of the Modbus interface, then again you should be able to receive the data in the emonPi.

Thank you very much for the detailed answers.

I meant clamp as in the CT itself not the act of clamping it :slight_smile:

Apparently that goes to the red/yellow isolator in the pic below and then to the inverter.

The BMS is inside the battery unit and communicates to the inverter via a cable.
The inverter has an rs485 port where the current wifi logger is connected - I’m trying to find out a way to piggyback off of it so be able to pull rs485 and send data to the Solis cloud - this will give me the battery values if I can get it to work as people have done here: Getting data from inverters via an RS485 connection - #26 by boydo

The value of this is positive when drawing from the grid and negative when exporting to the grid from the solar, is that enough?

Please share the link and I will do the reading :slight_smile:

The setup looks like this:

There’s another digital meter inside the little box to the right side which is not fully visible

Current transformers are not clamps. That has to be a mis-translation. In England at least, the device has always known in the industry and in the profession as a “current transformer”, a term which encompasses both the split-core and ring-core types.

You have already linked to it. We don’t take kindly to people who ask the same question in two different places. Take a few moments to read the first few points on the FAQ page.

It’s still not clear to me what the relationship is between the PV, inverter and battery. I think from what you’ve said, the “AC cable” does carry the nett power flowing between those units and the rest of your house, and nothing else. That power is bi-directional and it’s made up of two components, the power to or from the battery and any surplus power from the PV after charging the battery (not counting the inverter standby or operating powers).
A c.t. on that cable will show the total of those components. So to get the complete picture (assuming that’s what you want), you must find out, from the manuals and other documentation relating to your installation, where you can extract the data that gives you each contribution separately, or where you should measure to obtain the data.

Many thanks again for the reply :slight_smile:

Ok thought there was another post.
Not the same question, I asked for information on how to connect via rs485 to my inverter and a pi device, which will come in handy for the emonPI setup
I have gone through all the posts there and need to find out how to connect to my inverter using rs485 as it uses a proprietary connector.

I believe you are right, the AC cable that goes from the attic to my consumer unit must be sending both power from the panels and from the DC battery so no way to tell how much is coming from either of them unless I can pull this data directly from the inverter COM port.

I found this in milliseconds, searching for “Solis inverter RS485”. Does it look familiar:

If it doesn’t look hopeful, and you don’t have anything in manuals or other paperwork, you’ve got to hope someone else reads this and has the same make and model of inverter and knows the details.

Yup found that too on their site however the colour coding must be for the internals.
This is the plug type (wifi logger) but male on the inverter side

I did however speak to Solis support and they said they can send me a cable with that plug and hopefully cables that I can solder at the other end so I’m waiting for it to arrive.

If that will be the case then in theory I could connect that to an rs485 USB adapter (as specified in the other thread) and hook that up to the emonPI right?
The only question then remains if the protocol on @Ian999’s solis 4G matches my hybrid solis 5G or I wouldn’t be able to interpret the data using the same script.

Also if I do get that to work, does that mean I will not need the CTs on the emonPI since I’ll have that data directly from rs485?

Yes. RS485 is supposed to be a universal standard. However, you might find that the markings for the A & B legs have got mixed up.

You’re talking about two different things there. The protocol is likely to be, but there’s no reason to assume that it will be, the same. The data - the meaning of the values in each register - is likely to be, but there’s no reason to assume that it will be, the same, so if one has more “features” than the other, then you must expect to see differences.

If you can get all your data via the RS485 bus and Ethernet, there’s no reason to have an emonPi at all. The “emon” part is the analogue inputs for voltage and current, and the radio for receiving data from other “emon” sensors. If you won’t be using any of those, a straight RPi with emonCMS will do all you need.

If you can’t make a decision now, the “emon” front end (with the analogue part and the radio), the case and the display are all available separately in The Shop.

When I last looked into the wifi modules it was a common one for the Solis range.

If that is true for the 5G units too, I would be surprised if they have moved the default morbid registers for the process variables being transmitted as it will be the easiest way of maintaining compatibility.

Definitely worth a test to see.

I used a FTDI USB - RS485 adapter

Then you just need a pi, Emoncms and nodered (potentially not an emonpi, but you can still use the CT for the hot water tank and the iBoost)

I think you may be right, first I had tried the LAN stick first but the meter readings were crazy numbers (inverter values were ok) so I swapped it with a wifi stick after which they showed up correctly - apparently these are all Solarman sticks and Solis is about to release their own versions soon, both LAN and wifi.

If I can find out exactly how @craigcurtin wired his rs485 adapter on top of the logger so that they both work together it would be perfect - I assume just removing the plastic cover and soldering the data lines of the FTDI to USB adapter will do it but I would like to confirm before I attempt anything

I understand, and in that case I already have a rpi4 that runs my Home Assistant server so I could just get an USB to rs485 cable to that (provided true live data can be obtained from the inverter)

I dismantled my wifi stick to give me the correct connector.

I think I used a DVM to find the 0V line and then looked for the RS485 comms pins

Unfortunately I don’t have the notes I did when I made it and I bodged a connector housing on top which is then filled with potting to make it fit

I just took another look at my LAN logger which I still have

And going by the Solis documentation

Looks like pins 3 and 4 are for data. Does pin 2 (GND) also need to be connected or just the data pins?

I needed to have GND attached for it to work

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Ok so all but the power pin 1, need to be connected, since the rpi won’t need it as it has its own supply.
Going by the spec of the FTDI cable, should be Black → GND (pin 2), Yellow → pin 4, Orange → pin 3 (if you recall that is)

Would be ideal if I can hook this up to a raspberry pi zero that I have around instead of messing with my HA pi

The Pi Zero has a micro USB OTG port, so that should be possible.

If you can find an RS485-USB adapter with a micro USB connector, you’ll be able to plug
the adapter into the Pi directly. Otherise you’ll need an adapter with a connector compatible
with your RS485-USB module on one end and a micro USB connector on the other.

I do have a micro usb to normal USB OTG cable that I used in the past for connecting USB sticks to android phones so that would probably do it. Doesn’t seem to be that many ftdi micro usb cables out there

That sounds like it should do the job.

I’ve noticed that too. Seems the options are a full sized USB connector or tinned-wire ends.

I have used one of these with a USB OTG - USB-A adapter cable on a Pi Zero.

Yes just the 3 pins is all that is needed and the cable colours sound right, just tie the other ones out of the way and make sure they don’t short.

If there is a comms issue then the A and B lines are transposed, it won’t break it, so just swap them the right way round!!!

Nice, getting close to the solution :slight_smile:
Last part is to try is to replicate what @craigcurtin did, open up my wifi logger and connect the ftdi cable directly to the 3 wires of the logger so that I can both send data to solis cloud and do my own local queries for live data.
The reason I want to keep the Solis logging is that the battery warranty is reduced if not using that monitoring.
Do you see any problems with this approach? Won’t the signals get crossed when having two devices connected? Or it doesn’t matter as they are both slaves?

That’s exactly the point, RS485 is a multi-drop bus and they are slaves. You must never have more than one master on the bus. With Modbus RTU, you can have up to 31 slaves. (Modbus itself will accomodate 247 slaves, but the RS-485 driver hardware limit is 32 unit-loads) It’s the master that initiates each transaction, the slaves can only respond.