I went a different route. I have one RPI3b in my garage with 2 waveshare rs485 usb adapters that's wired to the 2 inverters in my garage. I'm running mbusd software on that RPI3b which basically serves as an rs485 gateway via wifi. On another NUC inside the house I'm running node-red which grabs the stats from mbusd on the RPI3b and after some mild massaging it stores that in an influx database. The data is then visualised from influxdb with grafana. I experimented with HA for a while but all the restarting due to semi frequent updates put me off. I prefer something that runs 24x7 without constant interruptions due to software updates.

Sounds good and you are obviously happy with it.. I'm using a WaveShare rs485 to ethernet converter so that bit is sorta the same bar the RPI is doing the conversion.  I wouldn't mind the stop starts if it worked in between 🙂 ...

I should have started another thread with the CT thing really. So I now have..  called SunSynk CT's I don't understand them.. 

A CT is simply a device to measure current passing through. It doesn't stop anything. It's merely there so the device using it can measure and take action, eg. throttle back output. But I guess you know this already?

Yep, I'm not new to CT's and that's why this is particularly  odd... 

I suppose this is what they meant with "fighting against each other", eg. 8kw start feeding power to a device in the house and then the 5kw also sense that something needs power and then there's too much power in total and it leaks out via the CT and the 8kw and/or the 5kw senses that and backs off. Maybe when they're properly parallel'ed (with comms cable between them) there's a bit more communication between the inverters so the one doesn't send more than what's needed.

The low current higher voltage DC is not a problem on long runs 

There is also the inverter input (string inverter) on Sunsynks if you want to send AC long distance   
 

as for the CT try to use a power meter (Chint or eastron) paralleling the RS485

RS485 can go to 1Km

2 hours ago, p_i said:

I suppose this is what they meant with "fighting against each other", eg. 8kw start feeding power to a device in the house and then the 5kw also sense that something needs power and then there's too much power in total and it leaks out via the CT and the 8kw and/or the 5kw senses that and backs off. Maybe when they're properly parallel'ed (with comms cable between them) there's a bit more communication between the inverters so the one doesn't send more than what's needed.

I think so far some of us agree you cannot parallel a 8, 5 and 3.6kW. This would have been the ideal way. 

Looking at this system if installed all at once 2x8kW would have been the perfect fit. 

Edited January 31, 20242 yr by Scorp007

6 minutes ago, Scorp007 said:

I think so far some of us agree you cannot parallel a 8, 5 and 3.6kW. This would have been the ideal way. 

Same size and firmware is needed to parallel 

55 minutes ago, Scorp007 said:

I think so far some of us agree you cannot parallel a 8, 5 and 3.6kW. This would have been the ideal way. 

Totally agreed.

@p_i Fighting on the dance floor is my only niggle. However they would have to have exactly the same response curve. The CT would see import. Inv1 would up its output voltage and start supplying that load. If inv2 was slightly behind then it would never get it's voltage higher than Inv1 so couldn't take over the supply. If inv2 was quicker it would take it but if they are exactly the same and ramp up together then they could maybe both feed but the amount they feed would be relative to their respective volts above the supply so in essences they would share the load. We spent a lot of time back 30 to 40 years ago in the uk revamping our power system stabilisers for each power station as the transmission system acted as a bit of a spring and put sufficient delays in that power stations YoYo'd  cyclically in feeding and backing off.. So I know this can happen but doubt the circuits in my house will have anywhere near the reactive components to cause this cycling.  If it was a quick job to disconnect a set of batteries and just plug them in to the other inverter I'd do it, just to find out. But alas it would be a decent install job so not easy and I wouldn't fiddle with any of the hardware whilst the dispute is raging. . If this is the case this would be an easy one for SunSynk to fix simply by putting an option in the inverter to slug the response. Ideally have the response on a time slot so one set leads in the morning and another in the afternoon then swap over the next day to ensure all the batteries etc get equal use. 

@Scorp007 2 X 8 kW  wouldn't be straight forwards though as they'd be in different buildings and one 8kw wouldn't have enough MPPT for the four PV strings (half south facing and half west facing).   The 3.6 and 5.5 was installed particularly for this reason. 

Everything and everyone seems to agree paralleling would be the best option but isn't possible. I can see why it is a bit of a challenge but can't really see why they couldn't be designed to parallel any size with any size as it's all controllable. Anyway its not so that's that but maybe in future as it probably only a software change.

@Yuri  The volt drop is important of course and the 3% in your example would be acceptable purely from a volt drop point of view.  However using your example the resistance of the cable is around 0.5 Ohm so the power loss over the cable would be I^2*R  = 200W . So do able but soon becomes significant when we are dealing with such small power margins.

I haven't really thought about the string inverter input ..of course on a big installation where distance is a problem and money no object you could transformer each end of an AC link to bump it up to say 1000V and minimise the I^2 losses. We do this on power stations to remote parts of the plant. 

That CT thing you posted. What is the advantage of that ? I would need a bigger one as my supply is 100amp.  What would be great is a single CT with multiple outputs. I have a CT for each car charger , each inverter and one for the heat pump. It looks pretty messy on my board. One Neat box with 5 outputs would neaten it up and ensure each inverter is getting exactly the same data. 

Remember the watt loss will go up and down depending on the current 

My setup is 2x 8KW Sunsynks with 44x  600W Canadian solar panels the inverters can only do 20800W but my panels are 26400W if you over panel it will just clip the excess

 

The CT wires must only be max 10M

 

 

If it is long distances there will be better accuracy and all inverters will get the same reading 

The Eastron one that I am currently using is 100A

If you want to try my Chint one you are welcome I am in Centurion 

 If you want a custom CT try V.A.C. Electrical Suppliers thy can make custom CTs

@Yuri  Would it be ok if I replied to this on my other thread as I should have really started a new one with these CT debates... 

 

 

no problem 

I've just heard a SunSynk engineer will be coming around my place to have a look at the problem on the 19th Feb. So not exactly speedy as the problems started in December but I'll be glad to get it working.  My problem now is going to be convincing them I don't just want the 8 batteries to work if there is a chance the four on one and four on the other will work.  I only agreed to buy and have installed the whole system as SunSynk said what I wanted to do would work. I was then forced to accept a variation in the install i.e. put all 8 batteries on one inverter as SunSynk change their minds and said it wouldn't work as a  4 by 4 . Thus the 8 battery install is done and if they come , do a firmware update or something and the 8 work they (installer and Sunsynk) will be great stuff job done. However if they were wrong about the 4 and 4 route then I'll want it putting back to as design and agreed. I feel this may be m next struggle.