Andre grobler

This can be done however, the territory you are in is micro grid status. This makes use of High Voltage Lithium and inverters...

So we are on a farm and have a system, with three rental units including our own house. Eskom line connection fee is more than the kwh related amount we consume. We want to go completely offgrid… because neighbours paid eskom r15k to go prepaid 3 years ago and they are still not converted…
Would it be feasible to install a system at each unit, and use the existing wiring to connect all the units into a private grid, so one could share excess power by prioritising load, battery then feedback to grid? And also use grid to charge batteries. Then if say someday we need more we can add panels or a new system anywhere on the grid…. Also it would then be feasible to utilise the various roof orientations better. 
 
i am assuming it can’t be done simply, as there is no global grid to push back to, the private grid will just be too erratic unless some systems are undersized and batteries oversized for instance. Maybe… and all the inverters probably need the same reaction time…
 

No aircon… luckily fairly well insulated… well, by design… not luck

No aircon… luckily fairly well insulated… well, by design… not luck

I got this BMS and it has a CAN/RS485 port...
LBSA DALY 100a 15S/16S 48V LiFePO4 Smart BMS with Optional Display or Bluetooth | Lithium Batteries South Africa (lithiumbatteriessa.co.za)
This is  pinout of the CAN/RS485 connector - DL-R16A-F16S100ATJ-MM00_Product_Specification_Confirmation_1.pdf (shopify.com)

Hi
As @GreenMan suggests our DALYs with Custom firmware has CABbus communication with Sunsynk inverters. 

You get VFDs that run off 3 phase.

VFDs usually have soft starting so it's highly unlikely that the rated current will spike by 2.5 - 3 times. 

Apparently the BMS monitors and manages the charging the temps and state of charge of each individual cell within the pack. It also can report the overall status to the computer or inverter. So, it safeguards everything. So i am assuming if your bms functions, it can accept or deny current from the inverter. We hope. Otherwise, you might as well be charging into the unknown, but probably be fine mostly
 
https://www.ufo-battery.com/how-does-a-lithium-battery-bms-work

I don't think it can deny current from the charger. In my understanding the BMS only informs. The only exception is the low voltage cut off. According to the datasheet of my Averge LFP it cuts off at 40.5V. I set the inverter cut off (29) to 42V.

Example of informative display of battery pack N° 3.

@Andre grobler

I know you have already spent a lot of time going the voltronics route, but really, do yourself a favour and look again at the Sunsynk with a lot more attention.
You can not go wrong with it even over Victron in my opinion. There are just too many positives and I think a select few negatives. It beats most of the competition with value for money. The features are best for the price and there are no compromises, except that it is a single unit vs separate units such as the Victron.
Otherwise, if you stay with the voltronics then at least go with the pylontech batteries.
 

Unfortunately, solar is quite a technical endeavour. So just as much as any newish up and coming industry, there are good and bad operators out there. 
But forums and chat rooms like these help to share and understand knowledge. Making the journey easier to embark on. I have no doubt your path whichever chosen will be a good one. But like in all things there are no guarantees. But at least you can ask and share here. Good pool of knowledgeable Ppl on this forum. 

Ja… out of the 5 installer suppliers we interviewed… only one could hold a logical train of thought… and understand what we want… so i am a little reluctant to start all over again… 

Ja… out of the 5 installer suppliers we interviewed… only one could hold a logical train of thought… and understand what we want… so i am a little reluctant to start all over again… 

Very simple...The forum support and ease of use of Sunsync is priceless! Remote control is also available...

No , the BMS merely tells the charger what the max charging current and max charger voltage must be at any given time. The Chargers honours this .   
There are two major benefits with BMS comms : 
 
1. The battery instructs the charger what the limits are . This is more safe and secure than allowing a user to play around with settings. 
 
2 the BMS may want to limit max charge and voltage even further at the tail end of the charge cycle. The reason for this is the cell voltage rises rapidly during this phase and outliers may cause the BMS to protect and switch off.  So BMS comms will prevent this rather gracefully. 
 
so the whole notion of smart BMS charging has a lot of merits. However there are no industry standard , so it's a compatibility hell out there , to the tune that lots of user give up on it.

I have no communication between BMS and inverters. But I monitor the batteries via hardwired RS485/USB cable real-time on a laptop very closely. I simply ignore the SOC display from the inverter, it's meaningless. On the other hand I monitor and control the Synergj/Voltronic inverters (2x MKS5K parallel) hardwired (RS232) alternatively on the remote panel or on another laptop with Watchpower. Yes, that requires me to go into the office but that's not that often. Even so my solar installation has become sort of a new hobby.

The solar assistant does not need WiFi, it can work as a standalone backbone system without networking. But one losses a lot of remote setting flexibility in doing so. 

Hi Andre,
The Phocos is a Rebranded Voltronics inverter. Phocos is a German company that imports the inverters from Voltronics in China and they are slightly different looking but the insides are Voltronics factory build, but under German quality control.
If I I was to embark on the same journey you are about to I would definitely go for the Original Voltronics machine just because it's slightly cheaper money and for the 5kW price of the Phocos you can get the 7.2kW higher spec Off Grid hybrid from Voltronics. 
Don't let the compatibly issues stop you getting the battery that you want. Solar assistant will bridge the gap for the inverter and it will work with just about any battery that exposes the RS485/ CAN via an RJ45 cable from the battery. So for the price of +-R3k you not only have now compatible battery and inverter Comms but also Real time system monitoring and it's on your mobile phone or any number of people that want to have access to the plant.
The Solar Assistant is a massive Bridge in the gap for not only Comms and it's becoming a global market leading tool for anyone that has a Voltronics inverter and any said battery.

I had a quick look at the spec sheet of the 5kw unit. There is quite a few benefits to the Sunsynk. You can have more PV 4,8kw DC to AC(6kw max array) vs 5kw DC to AC and 1,5kw DC to DC for a total of 6,5kw with the Sunsynk. Better efficiency from the battery and slightly better from PV. Better IP rating IP21 vs IP65. The most important difference IMO being 2 vs 5 year warranty and the user interface advantage. Im sure there are many more benefits to the Sunsynk than what i can think of right now but i would suggest you do your own research.

I would suggest you go with a more well known inverter like the Sunsynk.  If you do not have BMS comms with your battery you will not be able to accurately determine the SOC of the battery ,especially if its a LFP battery like the BYD and Pylons. This is because the voltage curve from 0-100% SOC is very flat and this makes it very hard to determine the SOC from voltage figures alone. When you have BMS comms the BMS can tell the inverter exactly what it wants and how it wants to be treated,instead of the inverter having to guess.

The simple solution is to get Pylontechs - or something that looks like a Pylontech to the inverter. There's hardly an inverter on the planet that won't get on with Pylontech.
Or try to see if SolarAssistant or a similar product can provide comms between the battery and inverter.