Posted by: @transparent

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chain

I believe that the diagram provided by @makia2023 shows chaining of the communication and earth, but the power cables connect up to the bus-bar.

Posted by: @transparent

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It must be an MCCB (Moulded Case Circuit Breaker) from a reliable supplier and capable of taking 200A or more.

Does something from aliexpress or alibaba counts as reputable? Does CE still mean "China Export" 🙂 This was why I decided to go for fuses with the pull-handle isolation functionality. Mersen do have a UK presence, so can (probably) be held liable in the event of a fault.

Posted by: @transparent

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That means you only use the 35mm² or 50mm² wire either side of the MCCB, mounted close to the inverter.

I believe the Seplos Mason 280L can handle 200A (depending on what version of the BMS you have, and software settings) so the system could just about operate with a single battery (the other being isolated for maintenance, for instance); the cells may not like it as it pushes them past their 0.5C continuous rating. Hence 35mm2 is specified throughout.

@transparent Acknowledge all of your points however as stated above, all this additional equipment means I will only have sufficient funds for 2 batteries initially. As per diagram i intend to use busbars. I have an electrician readied for the AC side however intended on have the cable run in for him to save time.

Ref MCCB - can you recommend one for a reasonable price? This?

Ref RCD/MCB/CT I have these already on the board from previous inverter (rated 30amps so will need to be uprated to 40amps AC side).

Otherwise I am quite happy.

I don't like the look of that MCCB you've located on ebay.

There are a few clues which cause me to feel uneasy

• the part number on the front label is SGM1-250Z but the description doesn't indicate who is the manufacturer
• go to AliExpress and enter MCCB SGM1-250Z into the search box at the top; it doesn't find such a product
• the ebay shipping details state that item is to be shipped from Jinhua, an area in NE China, which doesn't correspond with the seller's address lower down on the ebay listing
• enter the seller's address into Google Maps and it finds nothing at all similar
• the price is a lower than I feel comfortable with for a reputable MCCB on ebay
• for reasons I won't state here on the open forum, I suspect the seller is actually Russian

If you're going to have to wait for a shipment from China anyway, then why not go straight to a Manufacturer's Factory store on AliExpress?

I have bought, and used, trips of different sorts from a range of Chinese manufacturers.
But I haven't ever needed to buy an MCCB because I can use DC-rated MCBs for <125A

I like Geya. I queried why a particular 125A MCB from them was thinner than those made by their rivals, and received a competent technical explanation by email in good English!
However, the Geya Factory Store doesn't offer any MCCBs whilst the Geya Official Store does.
That's strange. I would use AliExpress Messages system to email the Factory Store and ask if they make MCCBs!

Chint is a good quality Chinese manufacturer, who already supplies products to electricians in the UK via wholesalers.
They're one of the few trip manufacturers who make a Type-B AC RCD which is used for EV chargers.
Type-B is sensitive to 'DC components' superimposed on the 50Hz AC waveform

But I can't find a 2-pole MCCB online.
Chint only seem to offer 1, 3 or 4-pole MCCB units.
Again, I'd email them and ask.
They will direct you to a recognised supplier in UK or Europe, but expect the price to be high due to the quality-assurance screening.

Other Chinese trip manufacturers to look at on AliExpress are Taixi, Tomzn, FEEO and Earu.
(Yes I realise that the FEEO store name looks odd, but I have satisfactorily been supplied with genuine FEEO products by them!)

The above explanation of buying Chinese electrical trips via AliExpress has come from experience gained with over 200 orders.
When it goes wrong, use the AliExpress complaints service. It works.

However, if I'm looking to have a technical dialogue with a manufacturer, and want more than one item, I almost always use the full Alibaba site.
That's not as easy to handle, and you are operating in a realm where suppliers are used to commercial terms & conditions.
Most members of this forum will probably feel safer by sticking to AliExpress.

@transparent ok looks good and I'm happy with AliExpress. Of course......sods law said that Fogstar would see out of the batteries and guess what .....they have of both package deals for 280 and 280l with 305ah envision. Opting for the grade A cells is gonna drive the price up another £800 which is too much. Ive contacted them to enquire on restock and hope it will be soon! Any other options I'm not aware of at a similar price/wh?

Posted by: @makia2023

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Any other options I'm not aware of at a similar price/wh?

If you can wait about 2 months you could always order through Alibaba! Per https://renewableheatinghub.co.uk/forums/energy-storage/fogstar-now-stocking-seplos-mason-boxes#post-20291, a few months ago 2 pieces of Mason 280 vertical boxes, 32 pieces of B-grade Eve LF280K cells, shipping and import were just shy of $4500 USD.

Note that it is probably not worth getting a Deye inverter directly from China (they do not have G98/G99/G100 approval).

@chickenbig interesting. 

Assuming I can source the kit I suppose I might be better having 2x inverters of say 5kw (104amps each so 125 amp DC side) this requiring smaller cables, fuses etc. Any sensibly priced makes/models that come recommended? Then I could just add extra units to either inverter battery "string" if/when required.

Posted by: @makia2023

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2x inverters of say 5kw

Sorry that I was unclear; the 5kW is the total system power. Many inverters that you can parallel together assume a common DC bus. The Sunsynk manual looks to need that, although their picture does not really count as a requirement. Perhaps technical support can confirm whether this is the case!

As a counterpoint, the very high powered Sunsynk inverters that use high voltage, like the 50kW 3-phase, allow each inverter to have their own battery stack. Putting 50kW into a 48V system would be quite unwieldy.

Yes, you are better off with 2x 5kW inverters, both in terms of cost and system resilience.

If you don't actually intend obtaining income from exporting to the grid, then you can choose hybrid off-grid inverters.
Permission isn't required from a DNO if no export is possible.
I've mentioned possible off-grid inverter manufacturers here in a previous post.

LiFePO4 cells in quantities smaller than a container-load can be imported at lower cost from agents you'll find on Alibaba.

Try contacting Brian Chen from Shezhen Xuba.
Last week he was offering EVE 280Ah cells at around $80 each, plus shipping +VAT.

The best shipping option is to choose DDP, which means that import taxes and VAT are sorted out by Xuba.
You just pay one amount on the Trade Assurance Form and that's it.

I recommend marine transport.
A 100Kg shipment will cost about $250 - $300.

If you wish, Brian will notify you of the exact ship onto which your consignment has been loaded.
You can then follow its progress using Marine Traffic, all the way from China to Felixstowe Container Port.

A courier such as DPD will handle it through UK customs for you, and deliver to your door.

I have just re-checked Xuba's Alibaba site, and it seems that they already have stock of LiFePO4 cells in a European Warehouse.
The cost is slightly more, but there will be shorter time before you receive the goods.

Send a message to Brian and ask his advice.

@transparent ok. 2x Growatt SPF5000ES seems suitable but I can't see an option for EPS function. I will redo my diagram tomorrow with a parallel inverter setup in mind utilising 150amp DC fuses. Any tips for the isolator between fuse and inverter now that the rating is lower? Will the 2 inverters be wired into separate fuses in the main board and then share the demand utilising CT clamps?

So this is my updated design. Am I there? Spotted the 25mm DC side will likely be better at 35mm or I could use trunked welding cable?

Also i've spoken to Brian and he can do me a really good price on some 310ah cells so only show stopper will be shipping time - which he is coming back to me with later.

Posted by: @makia2023

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I can't see an option for EPS function

Can you please define what you mean by that?
The SPF5000ES is an off-grid inverter.
When there is a grid-outage, all appliances which are powered from its 240v AC output will continue to operate because they're taking power from the battery(ies).

There is no possible requirement for a CT-clamp when using an off-grid inverter because they can never export back to the grid.

If you wish to retain a grid-export option, then you need to look at the Sunsynk inverters rather than Growatt.

If you wish to have a circuit in your house which can be switched to take its power either directly from the grid or from the battery/inverter combination, then you have to install a two-way 2-pole manual change-over. Here's an example of one such switch:

There are other switches which do the same function, but they have a centre-off position.
It's your choice, depending on what you're wanting to achieve.

As these are all DIN-rail mounted switches/trips, you can change your mind later and re-build the distribution board.
... or rather, your qualified electrician can!