matt1309 avatar image
matt1309 asked

Scalable system design ideas/suggestions


Current setup 2490w of panels on a shed and a growatt grid tied 2.5kw inverter.

My end goal is quattro plus batteries near incoming grid supply. Wire grid into quattro and have growatt as ac coupled system. Then add solar on house roof into battery (dc coupled)

However that end goal is very pricey. Any suggestions on an intermediary that minimises wasted parts.

I have room for about 10 more 2m x 1m panels on the shed (it's large and flat). My plan was 3.8kwh 12v battery with an old multiplus 800w model wired in as kind of a grid tied unit/ESS to output the battery later in evening.

Few concerns, I'm not sure how well multiplus will work in this kind of grid tied setup. Also feels like the multiplus will be wasted if I do pull the trigger on the monster end goal system of a quattro and circ 15kw of battery.

Love to hear suggestions/ideas on scalable systems. At the moment I'm guessing the advice will be don't bother buying anything and wait until I have funds for the big system.

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1 Answer
JohnC avatar image
JohnC answered ·

Hi @matt1309

It's really hard to suggest much. Even that little Multi and your existing ac-coupled pv will bob up against this issue..

And adding to a battery system as you build is usually something to be avoided. It's one of those things you might be forced into, but wouldn't usually do as a plan.

It is possible to add another Multi (or Quattro) later and combine them, providing you get the exact same model.

The only real advantage the Quattro has over the Multi is a second ACIN port, say for a generator. If you don't need that then there's a saving sticking with Multi.

Sorry I can't be of more help.

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matt1309 avatar image matt1309 commented ·

Hi John,

Thanks for the rapid response.

I see your point. I was hoping the Grid tied inverter would play nicely together with multiplus if both wired into the same grid (unfortunately only single phase where I am) but sounds like that's not the case.


grid -> loads

grid -> mutliplus (ac in)

grid -> grid tied inv

However it seems you're saying I'd have to properly ac couple it ie grid tied inverter plugged into the multiplus AC out and then multiplus have the grid plugged in via ACin.

grid -> (ac in) larger multiplus (ac out) -> grid tied inverter and loads.

Which you're right would mean I need a bigger mutliplus than planned to accommodate the grid tied inverter size. That's much closer to the end goal system setup I suppose. Sounds like scalable options are limited. In reality I just want an excuse to play with offgrid level solar gear but cant quite justify going all out just yet haha.

I think your suggestion of maybe multiple multi's is my best bet if I desperately want to do it now and expand by adding more in future. I was hoping to have a 100a transfer switch in my end goal system which I think some Multi's offer but I know the quattro 8kw and higher models offer. Unsure how the transfer switches work when inverters are in parallel.

I'm based in the country and plan for EV charger and ground source heat pump so we expect to need grid support hence the desire for a 100a transfer switch, do inverters in parallel allow for the sum of their transfer switch throughput?

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