Hi Guys.

Quick question. I have a Sunsynk 12kw 3phase inverter and 6.3kw solar array with two UP5000 batteries that was installed 18months ago.

Everything has been working fine but im now looking to add a third UP5000 battery to the system. My batteries are generally fully charged by 1-2pm and I use most of my power at night. 

My question is though that the original installer wired the batteries in series. i.e both batteries are mounted on the wall side by side below the inverter and both have cables going from the battery to the invertor but not to each other, then there is a data link cable between them only. The inverter reads the bms fine and sees 200ah. this is not usually how I see these wired though. should they have been in parallel? Im guessing he maybe did this as the link cables that come with them are super short and designed for them to be stacked on top of each other, rather than wall mounted side by side like he did.

If I add a third battery now should I change this or is it ok to just get another set of battery cables and put a third one on as serial, or should now chain together in parallel? presumably you can get longer link cables if I need to? 

noob question i know, but just want to double check before doing anything. 
 

They will be in parallel , you cant series these batteries, it will blow the BMS very quickly.  

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?

Edited September 14, 20232 yr by Danielhaynes

What, and the magic smoke hasn’t been let out?

 

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?

That sounds right.

 

That sounds right.

thanks... yea it wont obviously be as neat as stacking them with the short interlink cables but its effectively the same thing right? and easier to mount the batteries on the wall flat for me as it takes up less depth.

 

thanks... yea it wont obviously be as neat as stacking them with the short interlink cables but its effectively the same thing right? and easier to mount the batteries on the wall flat for me as it takes up less depth.

Not sure I'd put 3 lugs on each battery terminal on the inverter, that sounds like trouble. Why not just use interlink cables between the batteries to parallel them and then take a positive cable from the left battery and the negative from the right battery? You can still wall mount them like that.

Might be better to run your cables to a bus bar,then through a battery disconnect fuse and from there proper sized cable to your inverter.

Can't really comment without pictures to know what you have.

Or the other way....

Each battery with their own battery disconnect fuse unit onto + and - busbars, and then to inverter with the correct size battery cables.

 

 

thanks... yea it wont obviously be as neat as stacking them with the short interlink cables but its effectively the same thing right? and easier to mount the batteries on the wall flat for me as it takes up less depth.

Bus bar option sounds best as @Piper mentioned. Just ensure that the new battery is the master dip switch 1 on with can cable going to the inverter and on the other 2 all dip switches off only interlink cable going to them. hope it makes sense will PM you my number to explain if you are not sure

Edited September 15, 20232 yr by SYC

 

Might be better to run your cables to a bus bar,then through a battery disconnect fuse and from there proper sized cable to your inverter.

Can't really comment without pictures to know what you have.

 

 

Bus bar option sounds best as @Piper mentioned. Just ensure that the new battery is the master dip switch 1 on with can cable going to the inverter and on the other 2 all dip switches off only interlink cable going to them. hope it makes sense will PM you my number to explain if you are not sure

Thanks guys, really appreciate the help. I did some more research yesterday and came to the same conclusion, I didnt ever like the two cables sharing the same terminal in the first place which was the main reason for this post. So I think two busbar boxes and while im there add a disconnect fuse which I don't currently have at all. the alternative is buying the pylontech connectors and making longer interconnect cables between batteries but the busbar boxes will be easier and neater imo. photo attached of what I currently have and annotated with the changes. I dont need more current, extra battery is just to increase storage through the night and give a bit more headroom for occasional 4hr loadshedding blocks etc. plus I assume overall battery health will be improved sharing the load over three instead of two in general.  the inverter is set as max discharge of 90A which has been perfectly fine for us (generally house never really goes over 2000w in loadshedding, draws about 900w in the evening when we home watching tv etc and constant  400-500w during the night). 125amp disconnect box and 25mm battery cable all seems correct right?

Edited September 15, 20232 yr by Danielhaynes

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. 

 

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. 

Ok noted - Ill change the fuse to two pole then. Something like this (they do 125a or 160a fuse version, assume 125A still correct for mine): https://www.takealot.com/u2d-solar-dc-battery-disconnect-box-with-fuse-125a-2-pole-white-/PLID93228702 and do both positive and negative. Keeping the 90amp maximum discharge from the inverter. and up the cable from busbar to inverter. Cables from batteries to busbar will be the official pylontec 2m cables I already have and ill leave them all the same length.

Edited September 15, 20232 yr by Danielhaynes

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.

Oh yea I get that but there is only two of us in this place and everything in it is super efficient and new - dont think ive ever seen us temporarily peak much more than 6000w when we are running almost everything we have so not getting close to drawing the 90A max setting on the inverter atm. The only reason we have this particular inverter is when i bought the house it already had a 3 phase supply (which i dont need), and COCT insisted on the 3 phase inverter. I'm just after a bit more storage as we both work all day and any sunny day our batteries are fully charged by mid day, three batteries on a normal night gets me basically through the entire night off grid so should pay itself eventually (guessing 6-7yrs). 

Edited September 15, 20232 yr by Danielhaynes

This is the solar install on it just FYI - I have loads of space to add some more panels if I wanted (14 atm), but thats pointless for us without more storage. At least with the inverter I have room to grow if I ever needed. 

Edited September 15, 20232 yr by Danielhaynes

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

That chimney is in a very unfortunate position 😬 Why did they not use the roof right behind it with no shading issues? Nice house btw. Oh and are all those panels in one string ? Seems like it as the MPPT startup voltage wont be able to handle just 3 panels ... You are not really supposed to have panels facing in multiple directions on one string so you might want to look into that .  I would of split them into 2 strings of 7 panels ,or just move that 3 panels to the back roof with additional panels .

Edited September 15, 20232 yr by Nexuss

 

That chimney is in a very unfortunate position 😬 Why did they not use the roof right behind it with no shading issues? Nice house btw.

Thanks. Yea chimney isnt ideal but actually not as bad as it looks from that photo tbh. We went with that location as the run to the basement garage where the inverter is was already pretty hard work and we couldn't fit all 14 on the back roof as solar geyser takes up area. but I could easily add another string of 10-11 panels on there later If I wanted. Unless they change the stupid rules on back feed and make it worth our while I cant see me ever doing it though as I dont use enough power atm to justify it. 

Edited September 15, 20232 yr by Danielhaynes

 

Thanks. Yea chimney isnt ideal but actually not as bad as it looks from that photo tbh. We went with that location as the run to the basement garage where the inverter is was already pretty hard work and we couldn't fit all 14 on the back roof as solar geyser takes up area. but I could easily add another string of 10-11 panels on there later If I wanted. Unless they change the stupid rules on back feed and make it worth our while I cant see me ever doing it though as I dont use enough power atm to justify it. 

Okay i see . What is your production figures like for the year if i may ask ? i would think that chimney kills allot of production along with the 3 panels facing in a different direction .

 

Okay i see . What is your production figures like for the year if i may ask ? i would think that chimney kills allot of production along with the 3 panels facing in a different direction .

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. 

Edited September 15, 20232 yr by Danielhaynes

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. 

Edited September 20, 20232 yr by Danielhaynes

 

I'd change those voltages as well as a precaution.

 

I'd change those voltages as well as a precaution.

agreed.... what are the correct settings?

 

agreed.... what are the correct settings?

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