Posted by: @bontwoody

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Sorry Im reverting back to radiography mode!

Ah... someone with experience of radiography !

So if I help you with putting together a suitable battery storage solution,
could you advise me on the tokamak fusion reactor I'm constructing in the poultry barn at the bottom of the orchard?

It's going to be tricky getting the plasma toroid to form...
possibly due to instrumentation being limited to 10 TeV  😉 

Posted by: @bontwoody

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No one has ever suggested that possibility to me and the idea of charging the battery from both solar arrays is attractive.

... which is why you'll now be telling friends and family to visit this forum and ask questions, before hiring an installer!

It looks to me like the newer 4.3kW panels are divided into two arrays, for reasons we haven't yet calculated.
There are two pairs of wires going to your Huawei inverter.

If we want to add the existing 2.66kW array, then you need three MPPT (solar) inputs at the inverter(s).

Most solar inverters have one or two MPPT ports (not three).
But that problem is surmountable.

• either we find a way to connect the two new strings together (in parallel perhaps)
• or else you buy two inverters

Tell me everything you know about the spec of the 4.3kW arrays.

@transparent 

Yet another thing I forgot to mention 😁. The new panels are split 50:50 on East and West roofs

Im away from home at the moment so will find the spec out when I get back. 

I will mull over the fusion reactor specs while I drive but honestly I’d be better x-raying your back after the floor laying 😁

Ah yes. I'd forgotten the East/West split.
So you will require two MPPT inputs for that arrangement.

The Huawei Luna 2000 has a particularly low minimum voltage of 90v for the MPPT to start working.
That means the East/West handover will probably still work on a dull day.

A minimum 150v is more common for MPPT operation on an inverter.

So you'd need to build the system towards one with two inverters before you could re-direct the 2.66kW array towards the battery.

Everything I'm proposing here allows you to take small steps towards the hybrid off-grid system we're discussing.
You don't have to do the whole lot in one go.

@transparent OK, so am I actually going to need 3 inverters to achieve the charging of the battery from both arrays? Do you have any suggestions about which inverters I might need so I can include that in my sums 🙂

My quote on the newer E/W system is below

Of course actually there is still a fourth option (my null hypothesis 🙂 ) that it wont be financially viable to do. With this is mind Im going to monitor my peak and off peak usage closely over the winter months. I wont be getting the timber frame till the spring so it all fits nicely together. I know I dont use the grid significantly from May to August.

No. You need two inverters to incorporate the 2.66kW array.
Each inverter will have two MPPT inputs.

That still gives you one 'spare' input for renewable energy.
Hold that one in reserve for the DIY wind-turbine that you'll be eagerly constructing the following year 😘 

The inverters which best match your requirements are those from SunSynk.

SunSynk have obtained ENA approval for their system to restrict export to the grid, whilst having inverter capacity above 3.68kW.
Indeed most people are interested in limiting grid-export to Zero, which is a neat trick!
But you can increase it to 3.68kW as you wish.

The main wholesaler for JA panels in UK is ITS.
You can download the specification for the 385W unit from their site.

@transparent so two of these might do 🙂 https://www.bimblesolar.com/Sunsynk3.6kW-ECCO?tracking=googleshop&gad_source=1&gbraid=0AAAAAD-4VOyHsIWB0DtofX6eLdXY3R8IS&gclid=CjwKCAjwpbi4BhByEiwAMC8JnWX62iNtv9zY70EFduVLD2tUjFKGnrb1TV0okcIf231hND2-EhJAaxoCamcQAvD_BwE

Actually I was looking at a wind turbine before an extra battery but discounted it after looking at the ROI 😂

The SunSynk 5kW unit gives you more kW per £ than the 3.6kW you linked to.

I was suggesting a DIY wind-turbine rather than off-the-shelf.
If you have access to a stream, the RoI is better still for hydro-electric.
Both strategies use the same type of Permanent Magnet Generator (PMG) unit.

In the older SunSynk manuals there are instructions showing how to configure the firmware for direct connection of a wind/hydro turbine.
I can post details here when you come to that point !

@transparent So my thinking was that the new inverter needed to be 3.68 kW to satisfy the DNO, but I guess if the SunSynk can be limited to whatever then that doesnt matter. The older array doesnt need to be larger than 2.66 kW but I imagine they arent made that small much.

As the old Fronius inverter must have been there for at least 12 years, it may well need replacing soon anyway, so I can disregard that cost for the moment and just consider another £1000 in place of the Huawei one. The resale value of the Huawei kit is the unknown, but looking on ebay, I cant find anyone else selling one so I think there would be a market. I would certainly consider buying one at the right price 🙂

Thinking outside the box, would it be possible to use the Huawei luna batteries with the two SunSynk inverters?

In theory I would need to go through planning to have a wind turbine, but it does sound like a nice project. My house is in a good site for one on a slope and strong winds off the estuary 🙂 No stream Im afraid

Posted by: @bontwoody

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would it be possible to use the Huawei luna batteries with the two SunSynk inverters?

Yes. But when using batteries in parallel, you usually try to have them of the same capacity.
The Huawei Luna battery is much smaller than any which you are likely to assemble for yourself.

I hadn't realised that you're close to an estuary.

That's a good location for a small wind turbine.
The wind direction is generally more steady than occurs on high ground,
so the turbine head won't be swinging around.

Yes, you'd need planning permission.
How well do you know the Councillors for your ward?

Obtaining consent for a wind turbine requires two factors to be assessed:

• noise levels (see ETSU-R-97)
• shadow flicker; which is when the shadow from spinning blades passes in front of a window

Let's return to such matters once you've got storage batteries sorted.

@transparent 

I was musing that if I managed to get a cheap used Luna module I could just change the inverters to get both arrays charging the battery 🙂

Are there any problems with the SunSynk inverter and Fogstar battery communicating. I was having a read of this thread https://renewableheatinghub.co.uk/forums/energy-storage/new-fogstar-15-5kwh-upright-solution/paged/9 which seemed to suggest they might.

I probably not going to get any further with this until I have a better idea of my peak rate winter usage, but I will use the time wisely looking into the options and searching ebay for used Luna modules to get an idea of what they might be worth 🙂 Thanks for all your help.

By all means, keep musing away!
Adding a second Huawei Luna is more expensive in terms of £s per kWh.

I was never able to provide an adequate answer to those posts about a SunSynk inverter 'deciding' to recharge a Fogstar battery from the grid when its SoC reduced to 14%.

• Where was the 14% being measured: the BMS in the Fogstar battery, the front-panel LCD on the inverter, or the SunSynk App?
• Was the 14% measurement being noted whilst that grid-charge had just started? Coz the charge-current would distort the measurement.
• What parameter on the SunSynk inverter was determining that it should initiate an immediate recharge from the grid?
• Can the level of that parameter be changed, or the parameter disabled?
• Did it matter whether the user had coupled the battery and inverter with a data-lead?

There were just too many variables left unqualified by the two respondents.

My general overview is that a user needs to check out what possible benefit is obtained by linking the battery and the inverter.
If it's merely allow the inverter's App to display the cell voltages delivered by the BMS, then that's no more than a convenience.
But if the battery and inverter are exchanging commands between them, then what are those doing?

I've spent hours reading Modbus commands in documents from (Chinese) manufacturers, and they rarely apply the international Modbus standards.
So I'd be very wary of hooking up a data lead just because a manufacturer claims some sort of 'compatibility'.

And that being so, by not connecting a CANbus or RS485 comms link between a SunSynk inverter and a Fogstar battery, you can be more certain of which device is initiating an event.

The snippet above is taken from a SunSynk Modbus command document.

Unless your Mandarin is better than mine, how can you tell if setting these low-battery parameters will initiate a recharge sequence...
... and does that only take effect if the inverter believes it has a generator attached?  🤔 

@transparent -  This brings back memories of 25-30 years ago when I was responsible for shipping some crates of electronic equipment to China. I managed to find someone on an Internet newsgroup to translate phrases such as 'This Way Up', 'Keep Dry', etc into Mandarin so that I could attach appropriate notices on the crates.