Danielhaynes

Sounds like you are quite savvy there  you might want to look into getting a cable to connect to your console port on the battery so you can grab the history/events from the BMS and see why it was throwing alarms.  Go through this thread, the info is in there on how to do it .
https://powerforum.co.za/topic/2322-youdas-off-grid-lab/
 

Yea I worked out his bad CAN connection basically on week one. I mean all I had to do was read the manual and see straight away something wasn't right. So its basically always been working. I called them out to look at it and he blindly insisted right in front of me that everything was correct. In the meantime I had found the pinouts online and made my own cable, so plugged it in right in front of him and showed him right there as the CAN page lit up with all the correct readings how wrong he was. He then asked me how to make the cable 🤦🏻‍♂️
Anyway it makes sense that maybe if for whatever reason the CAN fails it would revert to inverter settings, even for just a second so im gonna have backup settings on the inverter low at 52.5v across the board and then just see if i get a random alarm again at some point. its so intermittent that i might have to wait a few months. 
New battery looks great though.. charged to 100% today and is now gradually on its way back down with no issues so far. the way ive cabled them all up is also miles better than the installer so that may also help the intermittent alarm. 

The BMS link should set the voltages but I have a recollection that someone on here mentioned that the batteries will use the settings if the CAN fails. I think their was a link to a YouTube video about it. (It may have been on another forum that it wa mentioned.)
 
Personally I would expect the inverter to shut down but I don't have your inverter.

I'd personally set it a little bit lower at 52.5v. That's enough for the batteries to balance.
(I run mine at 53.2v once a week (until it gets to 100% SOC) and 52.5v for the rest of the week).

53,2V for everything , also set your discharge amps up from 90A to 150A

Finished installing the new battery today as per my plan. Just need to tidy up with some extra trunking this week etc to hide the new cabling. 
All went super well, balanced the batteries until all the lights went out and made the new battery the master - all the data connections are working and turning on the master battery turned the other two on in sync as expected. They are talking to the inverter fine and see it upped the max available charge/discharge according from 100A to 150A. now busy charging up from solar. 
I've set charge to only 75A as thats all my panels would be able to supply anyway and max discharge left at the existing 90A, all well within the cable, fuses and lugs I have used. All the other battery voltage settings are as per the installer though... can someone confirm they are correct as to be frank I don't have much trust in him at all which is why I did this addition myself. (probably doesn't matter as the BMS should override voltage settings anyway right?) 
The original installer didn't even leave me with a working LiBms link as he just plugged a standard network cable as a can cable and swore to me that he was correct. Following some research I saw its totally wrong and has to have the correct pin outs from Pylontech to Sunsynk.  I made my own cable and it immediately worked. God knows how many of his customers he leaves in the same incorrect state as he does installs every single day (its a big company) and said this is how they always do it! I have a background in IT networking/hardware so the data side is easy for me, most other customers just wont know any different im sure. 

According to the app since June 2022 ive generated 7900 units. But in the summer half the day im sat with 100% batteries and the house only pulling 500w while im at work so I could have made loads more. I put a heat pump on the pool mid summer just to try and pull the excess I was wasting which worked great, but it wasn't long until my pool was at 36oC (which felt like a bath) and the solar was once again sat idle all afternoon. It really is stupid that you cant just wind your meter back like the UK... We sit with all this loadshedding but people like me would plonk a bunch more panels on their roof and backfeed the moment they allowed that. - At the moment they want to charge a ridiculous amount just for the privilege to back feed and they pay you next to nothing for the units - just isnt worth it for a small system like mine, last time I looked I would actually loose money. Thus i might as well try and use more myself with another battery 
 
The three panels on the other roof actually work nicely in the winter when the sun moves round (they said I could put panels on the long roof at the back to really help the winter if I wanted).. that was the thinking behind that. In the summer I have seen the whole lot hit a peak of 6000W which isnt far off the max, so at least roof direction seems ideal. 

The battery disconnect should work but not my favorite. I prefer the Mersen 2P-160A. Also note that with 125 A you will never be able to draw full current on the inverter from batt in the future. Even the Mersen 160A isnt big enough seeing that the max the 12kw Sunsynk can do is 240Amp.

Some of us will call that a castle not a house🤣

Please ensure that all the battery cables are the same length. Fuse should disconnect the Positive and Negative. 25mm cable from batt to fuse/busbar is fine. From there I would use 50mm to the Inverter. 

each battery has 2m cables that go to the same +/- terminals in the inverter. So yes im being stupid... 
So what im asking then is if its ok to just mount a third battery on the wall next to it and do exactly the same, i.e have three cables on those terminals (I actually already have a spare set of 2m pylontech battery to inverter cables), one pair to each battery rather than stacking them and using the interlink cables? Link the new battery to the group with a data cable and it will then see 300ah instead of 200ah?

Thanks for the update.. appreciate it 

Its not really a massive issue... more an annoyance that I always assumed would be fixed, but great to have confirmation. 

Update:  SunSynk Support have confirmed they are aware of the 12kW 3-P graphing problem and attempting to resolve it as soon as possible. 
No defined ETR.
 

I came here looking for exactly the same fault. I’m also on a three phase 12kw and am getting the exact same 65k grid spikes on my graph since 25th. So clearly this is a logger fault and not with our system. Hopefully it’s fixed soon. Graphs are now useless