Solar system mains voltage current sharing.

[Normandie]

Hello, firstly I am new to all forums but cannot find the answer to my questions from trades people. I am English and live in France. I have four solar rotators complete with ten 400 watt panels on each. I was using two 8 kwh inverters in parallel (c/w inbuilt MPPT) and six Pylontech US3000c batteries. I had problems from day one with communication problems, error messages on batteries and inverters that got worse and worse over several months. The inverters would not speak to the dongles either. Eventually the electrician decided to disconnect the inverters because they were constantly tripping the house mains. The inverter company seemed totally lost and despite answering every question asked providing the data requested and extensive photographs they were at a loss. For clarity we did have communication between the batteries and the inverters however the panel kept changing the error message numbers. We then decided to change to a Victron Multiplus - 11 230 v 15 200 100 kwh + four MPPT's and various Lynx and Cerbo GX , Cerbo touch 50 and Cerbo S GX. All good so far.
We have five unused SOK 5kwh batteries 48 volt 100 ah. I have seen information on Current sharing but have not seen anyone actually give a breakdown of of how to do this. Now to the questions please. Firstly can I connect the mains power (230 volts ac) to a second independent electrical fuse box and then a separate inverter with these batteries and use more solar panels so that I have two complete solar systems. What security systems would need to be designed in? Would the two AC systems work together without issues. Secondly, can I connect the batteries safely I.E. Pylontech in one stack and SOK in another stack and share the solar panels. Would I need different DC fusing? What safeguards would need to be installed. The existing solar panels charge the Pylontech batteries on sunny days in around three hours so capacity is great. My only issue is that I need more battery power.
I understand that I am a newbie but please do not just shoot me down without explanation. I see many youtubers regularly connecting multiple batteries etc to their systems without any problems. Thank you in advance in anticipation of you help and please....kindness.

 

[timselectric]

Some (maybe all) 48v Pylontech batteries are 15s, instead of the standard 16s. For this reason, I wouldn't recommend combining them with the SOK batteries. (Different charging parameters)
As far as the separate system, that's not a problem.

 

[Normandie]

Thank you Tim. Connecting a separate system then, what do I need to cover in respect of the two AC connections? I assume fused circuit boards but how do I connect these. Do I have to have safeguards over back feeding one system into another or do I put two fused circuits into a master circuit board. Please excuse my lack of knowledge but I am really trying to grasp the basics. Also thank you with regard to the 15s and 16s. I was aware of this but do see the tests that so many people on these LifePo systems.

 

[timselectric]

Both systems need to remain separate from each other. The only thing that can be common between them is where they get their source from.
Each fed from their own breaker.

 

[Normandie]

Thank you again. Just thinking this through in my own mind here so, If I use the Victron Multiplus 11 inverter on the existing set up should I also use another Victron on the second set up. The reason that I ask is whether the output of the Victron has different phasing or anything to A N Other Inverter.

 

[SamDeleted]

Connecting a separate system then, what do I need to cover in respect of the two AC connections?

This is all very dependent on local laws ?

 

[timselectric]

Thank you again. Just thinking this through in my own mind here so, If I use the Victron Multiplus 11 inverter on the existing set up should I also use another Victron on the second set up. The reason that I ask is whether the output of the Victron has different phasing or anything to A N Other Inverter.

No
They don't have to be the same brand.
They all synchronize to the grid. Not to each other.

 

[Normandie]

Thank you Sam and a very good response. I live in France so have to use a French qualified electrician. Solar here in France is not common and it is just starting to become known to the public. Trying to find a Solar expert here is difficult. Wiring and sockets etc are different to the UK for instance but very similar to European specifications. Victron is establishing its self here and has a French outlet so this is good. What I have done previously was use some of the plans that Will Prowse supplied when setting up the original Solar system and then sat down with my French electrician who checked local regulations. What I am trying to do is find what the basic layout would be for a situation and then adapting from here. Sorry if this is gobbledegook. Running two sets of batteries (SOK and Pylontech) for instance has been hard to understand but I think that we are getting there. If we can couple the mains AC than that is good. I just need to see about splitting the solar panels between two inverters and the two batteries and hopefully be away. Any advice will be gratefully received especially drawings and specifications. Thank you.

 

[Normandie]

No
They don't have to be the same brand.
They all synchronize to the grid. Not to each other.

Thank you Tim. My previous inverters were MPP. I am loathe to use them again as back up and support was so very poor. Such a shame because the pre sales service was exceptional. After sales does not appear to have been thought of.

 

[SamDeleted]

I live in France so have to use a French qualified electrician.

Does he show up on time lol ?

 

[Normandie]

I must admit this one does. He is very thorough and quick. It did take me very many different people before I found this one though!