Parallel Inverters

[Mrjmegson]

Hey guys, I'm after the pros and cons of paralleling my inverters.

Some of you will know I've just decided to change Inverters, and the new inverters I'm going for allow me to parallel them.

Recap
My system is 2 roofs, each with 16 x 400w panels (an east and a west facing roof)

2 X 6kW inverters, one for each roof.

8 X 5kw batteries, split into 4 for each inverter.

So, is there any benefit to paralleling the inverters? Would this mean having one stack of 8 batteries?

What are the pros and cons?

Cheers,

Jay

 

[binky]

Hey guys, I'm after the pros and cons of paralleling my inverters.

Some of you will know I've just decided to change Inverters, and the new inverters I'm going for allow me to parallel them.

Recap
My system is 2 roofs, each with 16 x 400w panels (an east and a west facing roof)

2 X 6kW inverters, one for each roof.

8 X 5kw batteries, split into 4 for each inverter.

So, is there any benefit to paralleling the inverters? Would this mean having one stack of 8 batteries?

What are the pros and cons?

Cheers,

Jay

Easier to connect as two circuits. Can't see any advantage in doing anything else.

 

[Mrjmegson]

Easier to connect as two circuits. Can't see any advantage in doing anything else.

So stick to my original plan then.

I wonder why they allow you to have them connected.

Question. Will my inverters share any loads equally when connected as two circuits? If they both have capacity that is.

 

[binky]

So stick to my original plan then.

I wonder why they allow you to have them connected.

Question. Will my inverters share any loads equally when connected as two circuits? If they both have capacity that is.

Suits larger installations.

As for load sharing, should work fine, although I've never actually tried it with batteries.

 

[Mrjmegson]

Cheers Binky

 

[arwooldridge]

Two systems each with batteries, working independently, can interact badly. You get cross cycling, which I have observed, where one system discharged into the other charging that up, and vice versa alternately. The reason this can occur is the threshold for feed in are typically very similar, so which one decides to charge or discharge is fairly random. If the two thresholds are sufficiently different (eg 100watts and 300watts) the system may work. It's better to use master/slave connected systems if the inverters allow that. Alternatively two or more PV inverters would work independently ok if only one or none have batteries.

 

[arwooldridge]

PS a better solution for east/west may be a single hybrid inverter with two MPPT input strings, but you are limited on how many batteries you can connect.

 

[bladerunnerpv]

12.8kWp into one hybrid single phase inverter? Are you aware of anything which can do this?

 

[arwooldridge]

12.8kWp into one hybrid single phase inverter? Are you aware of anything which can do this?

Sorry I was thinking 3 phase, Solax do 15kwatt 3 phase hybrids with dual MPPT. But you don't necessarily need a12.8kw capable inverter, 10 kw would work well if they do single phase ones, just lose a bit around midday in summer when you probable don't need that power. Inverters just throttle down to their peak capacity. 12.8kw is some serious current on single phase though. You might need to restrict export anyway once batteries are full to comply with DNO.

 

[bladerunnerpv]

Hi arwooldridge, the OP has eventually managed to solve this by using two single phase hybrid inverters in parallel, see other threads for details if interested.

 

[Mrjmegson]

Two systems each with batteries, working independently, can interact badly. You get cross cycling, which I have observed, where one system discharged into the other charging that up, and vice versa alternately. The reason this can occur is the threshold for feed in are typically very similar, so which one decides to charge or discharge is fairly random. If the two thresholds are sufficiently different (eg 100watts and 300watts) the system may work. It's better to use master/slave connected systems if the inverters allow that. Alternatively two or more PV inverters would work independently ok if only one or none have batteries.

Cross Cycling. That's definitely what I experienced when I first set them up without connecting them up to each other via coms. They started charging each other batteries and just generally fighting each other. Carnage. Lol