Monitoring & Controlling a Hybrid Solis Inverter

[sharpener]

I intend to have a go at getting one of these to control our heat recovery ventilation boost, as the existing humidity sensing boost control doesn't work as well as it should.

I wondered about this. In the end I decided to mimic the timer on an ordinary bathroom fan i.e. operate it by the light switch instead.

The Villavent MVHR system doesn't have an accessible UI but does have 4 different fan speeds. So I fitted a mains c/o relay which when energised increases the fan speed by one increment by changing the transformer tapping.

Tiny piece of Veroboard (housed in a CH wiring centre - lots of terminal blocks and strain relief) then has a handful of analogue parts, a good old 555 timer chip and tantalum cap set to give an 8 min run time, powered by a capacitive dropper from the mains, driving a small triac to pull in the relay.

Worst/best bit of the design is the mains OR-gate whereby any of the 4 light switches (each connected via a 470k resistor and diode) trigger the 555(!)

Not quite in @MrPablo's league for control logic I fear.

[Oldgreybeard]

I intend to have a go at getting one of these to control our heat recovery ventilation boost, as the existing humidity sensing boost control doesn't work as well as it should.

I wondered about this. In the end I decided to mimic the timer on an ordinary bathroom fan i.e. operate it by the light switch instead.

The Villavent MVHR system doesn't have an accessible UI but does have 4 different fan speeds. So I fitted a mains c/o relay which when energised increases the fan speed by one increment by changing the transformer tapping.

Tiny piece of Veroboard (housed in a CH wiring centre - lots of terminal blocks and strain relief) then has a handful of analogue parts, a good old 555 timer chip and tantalum cap set to give an 8 min run time, powered by a capacitive dropper from the mains, driving a small triac to pull in the relay.

Worst/best bit of the design is the mains OR-gate whereby any of the 4 light switches (each connected via a 470k resistor and diode) trigger the 555(!)

Not quite in @MrPablo's league for control logic I fear.

Ours also has four fan speeds, with three of them being programmable for any percentage of full speed needed to get the correct flow rate. The humidity sensing on the extract duct air is also programmable, but this needs to be changed with the seasons/weather. Right now it's set to come on at 60% and off at 58% RH, in dry weather I turn this down so that it turns on at around 55%, because it often won't get as high as 60% at times.

Ours also has a manual boost from a button on the control panel, in increments of an hour, up to three hours, that we use when cooking, if the humidity sensor hasn't triggered. There's also a dry contact input on the unit itself that can be used to trigger boost, and it was this I was looking to use to override the default duct air humidity sensing. I think that something like a 2% rate of increase in RH over 2 minutes should be about right, and one advantage of doing it with an ESP module is that I can use a simple and portable WiFi button to boost the system without needing to use the control panel. Could be useful to have this button in the kitchen.

[MrPablo]

I did some investigation last night and found a ESP-Home config that handles Solis Modbus. A different inverter model, but at least it's something I can reference.
If I shift to a esp32 in the garage to control the inverter, I might as well hook it up to relays to control the outdoor lighting as well.

[Oldgreybeard]

Does anyone happen to have the pinout for the DB9 connector used on the Solarman LSW-3 WiFi logger stick, as often used with Sofar inverters, please? I'm pretty sure the pinout is common to more than one inverter make, as it looks as if the Solarman app works with a few different inverters.

I could rip apart the stick and reverse engineer the connector wiring, but it seems easier to ask here in the hope that someone has already done this. I've spent a couple of hours searching the web to see if I could find it anywhere, but with no luck. My reason for needing this info is because I'd like to be able to use one connector to the inverter to both connect to the RS485 data and to draw a small bit of power from the inverter to run an external interface (saves having a separately powered interface box). The spec for the LSW-3 suggests that it can use up to 1.5W at between 5V and 12V, so there should be plenty of power available from the inverter to run an alternative WiFi interface (I'm looking at using the Elfin module mentioned earlier in this thread).

[Oldgreybeard]

If I shift to a esp32 in the garage to control the inverter, I might as well hook it up to relays to control the outdoor lighting as well.

I recently bought some ESP32 relay boards cheaply that seem to work well. I opted for ones that include an AC power supply, as they make for an easy to use way to switch things like lights on and off. I bought a four channel board like this one:

4 channel relay board.jpg (104.5 KiB) Viewed 2330 times

plus a couple of two channel and single channel boards:

They all look OK in terms of electrical safety, with an isolation slot routed out between the mains side parts and the DC side. These boards do make putting the hardware together a fair bit easier.

[MrPablo]

That board looks to be a pretty decent option, particularly as there's easy GPIO breakout.
One to order today I think!

[Graham]

I am a newly registered complete beginner. I am extremely impressed with and intrested in your node-red flow to control the Solis inverter. I can confirm that it appears to work using the Solis wired LAN datalogger type WL. There seemed in my case no necessity to change to a different one.

There are many aspects which I do not yet understand and will be asking questions with your permission. I will be trying your percentage charge controller during E7 tonight. However, one aspect which disppoints me is that as soon as I run your flow, the Solis cloud app stops accumulating data for graphs. I have tried increasing the inject period as far as to ten minutes, but it still won't work. I would like if possible to keep the graphs as well; am I being greedy?

Thank you

[Fintray]

Welcome to the forum Graham.

[MrPablo]

Hi Graham, welcome to the forum!

It looks like the S2-WL-ST won't accept multiple connections so if you use local modbus (via NodeRed, for example) then it'll disconnect Solis Cloud.
I'll have a look and see if there's any workarounds, but I don't have too much hope.

Out of curiosity, what sort of graphs do you tend to use?
Perhaps they can be replicated as part of a basic NodeRed dashboard.

[Graham]

Thank you very much for getting back to me.

The S2-WL-ST is indeed the datalogger I have. So is there a continuous modbus connection to the datalogger whenever there is a node-red flow running? I had (wrongly apparently) imagined that a connection was established and subsequently dropped every time an injection took place so if I increased the interval between injections it could handle both my flow and the cloud.

The kind of graphs I would like are the regular ones; PV output, battery power, battery SOC, grid power, house consumption etc. I would love to add them to the node-red flow; it will be quite a learning curve for me though!

Please can you tell me; is any use made of the maximum discharge current in your Auto SOC strategy?

Thank you.