Axpertking 3x 5KW parallel with Pylontech US300 - ADVICE PLEASE

[NoviceSolar]

Hi there

I am pretty new to all this and require some advice please. I am fitting a single phase 15KW system with four US3000 Pylon Lithium batteries

I have bought three Axpert/Conversol 5KW inverters with parallel cards.

They will be linked to a 24x310w panel array (2x4(x3) panels in series and then paralleled through 3 combiner boxes to a single cable to bring power into the building in a 25mm SAW Cable. I will then parallel the power out into each inverter through 3x30A DC breakers.

I intend then to take the 5KW AC output, parallel that into a 125amp changeover switch (with our 9Kva Lister TS3 geneset) and then onto the property's domestic distribution board.

The four Pylontech US3000 batteries are paralleled together as per instructions and from what I gather the Pylons (with their coms cables) are wired to one master inverter, with the other two inverters set to be 'slaves'.

Can anyone give me advice on how to wire up the inverters in parallel? preferably a diagram?

I assume the following:

1) PV power (DC) goes into each Inverter (via 3x63A breakers)

2) AC power comes out of each inverter and I will parallel that on a busbar (or similar) to my distribution board

3) Pylon-tech batteries (via 20A DC fuse disconnect) go to the master inverter with BMS (set to PLY)

How does (A) the battery bank get charged from a single inverter and (B) how does the battery power get distributed to the other two inverters?

Am I missing something about wiring the other inverters together parallel to distribute the DC power from the batteries??

 

Many thanks and please be gentle with me - not too technical with any answers.

 

[jykenmynie]

Just something to consider: In my opinion you are significantly underspeccing on batteries. Why do you need 15kVA of inverters? If you need it because your demand is that high, you need at the very least 15kWh of Li batteries, but preferably much more if you go Pylontech. Their BMS is strict against abuse and are happiest at 37A continuous discharge.

Do you really need three inverters? Isn’t a good hybrid inverter a better option (I don’t know your specific use case, just asking).

[Calvin]

2 hours ago, NoviceSolar said:

paralleled through 3 combiner boxes to a single cable to bring power into the building in a 25mm SAW Cable. I will then parallel the power out into each inverter through 3x30A DC breakers.

Each inverter needs to control its own panels.  You need to bring in 3 cable pairs, each with 8 panels.  Your breakers will need to be 40A as you will have 2S4P on each inverter.

 

2 hours ago, NoviceSolar said:

Can anyone give me advice on how to wire up the inverters in parallel? preferably a diagram?

2 hours ago, NoviceSolar said:

How does (A) the battery bank get charged from a single inverter and (B) how does the battery power get distributed to the other two inverters?

Am I missing something about wiring the other inverters together parallel to distribute the DC power from the batteries??

All the wiring is explained in great detail (with nice diagrams) in the user manual https://www.mppsolar.com/manual/PIP-MK (PF1.0)/PIP-MK manual-20190717.pdf

 

1 hour ago, NoviceSolar said:

3) Pylon-tech batteries (via 20A DC fuse disconnect) go to the master inverter with BMS (set to PLY)

No - batteries are connected to all 3 inverters via busbar.  That answers both questions (A) and (B)

One huge issue: current firmware (71.93 / 02.49) has many bugs.  Kings in parallel in PYL mode simply do not work. (they are supposed to).  You would need some external management software like ICC to make it work properly.

Also, I assume 20A DC fuse is typo: 15kW @ 48V is over 300A. 

 

[Coulomb]

16 hours ago, Calvin said:

Each inverter needs to control its own panels.

Yes. On other models, you could blow up at least the solar charge controllers doing this.

18 hours ago, NoviceSolar said:

How does (A) the battery bank get charged from a single inverter and (B) how does the battery power get distributed to the other two inverters?

You need fat (35 mm²) cables from a bus bar to each inverter. Each inverter should have its own DC rated fuse of about 100 or 125 A. It is possible for one inverter to do the majority or even all the charging, but usually it works out best to spread the charging over the three inverters.

[Plaashaas]

18 hours ago, NoviceSolar said:

They will be linked to a 24x310w panel array

You can also add another 3 panels and wire them 3S3P x3. Pending your roof or space, consider doing one of these arrays facing east. You always need that early morning power for the batteries. 

18 hours ago, NoviceSolar said:

with four US3000 Pylon Lithium batteries

Get a extra set of Pylontech cables and wire the bank from "both sides" (Using opposites for each set)

18 hours ago, NoviceSolar said:

one master inverter, with the other two inverters set to be 'slaves'.

You don't set the slaves or master, it is randomly assigned. On my system it seems like you can manipulate the assignment by starting the master a couple seconds before the slaves. (might have been random luck on my side)

Otherwise you just start them all, check which one is the master and plug Pylontech comms into that one. The slave will give 61 errors. 

29 minutes ago, Coulomb said:

You need fat (35 mm²) cables from a bus bar to each inverter

Make sure the cables are the same length & Spec for each inverter. 

[Calvin]

1 hour ago, Plaashaas said:

You can also add another 3 panels and wire them 3S3P x3

You need to be careful here.  Most 310W panels are 72 cells.  It is marginal but 72 cell panels in 3S is NOT a good idea with 145V inverters - I have had to re-wire mine to 2S after plenty of problems caused by over-voltage in the SCC.

See this post for more detail.

 

[Plaashaas]

1 hour ago, Calvin said:

You need to be careful here.  Most 310W panels are 72 cells.  It is marginal but 72 cell panels in 3S is NOT a good idea with 145V inverters

I am running 330W in 3S4P. Yes I sometimes go over 130V but that is rare occasions with cloud edge or cold wind, maybe. 

[Calvin]

11 minutes ago, Plaashaas said:

I am running 330W in 3S4P

So did I, for several months.  That does not mean it was clever, or sustainable in the long term.

I thought that @NoviceSolarshould be aware that the advice you gave him is not universally considered to be good practice.  I am not trying to tell you what to do.  If you read the comments by @Coulombin the thread that I linked and still want to do it, go for it.

Edited September 2, 2020 by Calvin

[Plaashaas]

31 minutes ago, Calvin said:

should be aware that the advice you gave him is not universally considered to be good practice

 My life story.