OK, let's spec this system.

[SafetyThird]

After all the back and forth on my other thread, I'm now ready to actually spec and purchase a battery backup system. I've decided against the Victron setup simply because so many people talk about the noise the Multiplus 2 makes and, as the system is going to be indoors, noise is a major factor. I've also decided not to worry about additional PV etc yet. I can always add a hybrid inverter/battery/panels to the other phase of our split phase supply later, or perhaps put that money into investing in Ripple which may give better results in the winter. So, a simple AC coupled inverter and batteries with the ancillaries to connect it all and have a backup circuit to which I'll connect the house lighting circuits and one ring main that powers the office.

I'm planning to go with 4 x Pylontech US3000C batteries, to give me a battery size of 14kwh. Plenty to get started with and can be added to later as needed. The main choice now is the AC inverter. There's 3 I've been looking at: The sofar ME3000SP, the Solis 3Kw 5G RAI and the Luxpower ACS 3600.

The first two seem to have near identical specs with max charge/discharge of 3000w/60A and 3000w/13A for a backup circuit. The Luxpower has max charge/discharge of 3600VA/70 and backup output of 16A/3600VA, which looks like a better option if price is similar. I can't seem to find a price for the Luxpower on it's own, just with a battery kit.

Does anyone have comments/suggestions based on real world use for these inverters or any reason I shouldn't go for the Luxpower?

[Swwils]

Get the lux hybrid. I really like it.

It can also charge the battery at full rate and send to grid at the same time if you have an array bigger than 3.6kwp.

[SafetyThird]

Hmmm, that would require DNO involvement (more than the soft touch permission an AC system would require) and changing my inverter my cause issues with FIT payments. I have 6kw of solar, limited to 3.8kw by the Sunny Boy inverter.

Mind you, would make it very neat if I did as it would replace the sunny boy inverter and there's room beneath it for 8 batteries in 4 sets of 2 on wall mounts. With just the AC inverter below the Sunny Boy, there's just room for 4 batteries in 2 sets of two wall mounted, but sitting on the floor.

[Countrypaul]

I would leave your existing FITS system alone, the last thing you want is some minor change invalidating the whole system and losing FITS.

Given all three solutions you are looking at have very similar specs, why not get some quotes for supply and see if there are any major differnces, or whether any supplier proposes something else that you are not aware of.

[nowty]

Hmmm, that would require DNO involvement (more than the soft touch permission an AC system would require) and changing my inverter my cause issues with FIT payments. I have 6kw of solar, limited to 3.8kw by the Sunny Boy inverter.

Do you have a 4kW Sunny boy capped to 3.8kW ?, or do you mean 3.68kW. Or is it a later 3.68kW version Sunny Boy ?
In the olden days of FIT you could sometimes get away with a 4kW inverter capped to 3.68kW under the G83 rules, until the DNO's clamped down on that behaviour.

If its a 4kW Sunny boy, even if you've capped it lower you could officially only go with the 3kW battery inverter with the light touch G99 application as the total inverter power would be less than 2 x 3.68kW = 7.36kW.

Replacing the existing sunny boy with a hybrid is generally a no no because of the FITs unless you get complicated with a bi directional generation meter.

If your Sunny Boy is a 3.68kW version I think you could add an additional hybrid with or without extra panels on the same phase and still do the light touch G99 application assuming the hybrid is G100 compliant. The problem is the whole system on the single phase needs to be G100 compliant which it may or may not be depending on how the hybrid behaves with the existing inverter.

If I were would I would stick to your plan of an additional AC coupled battery inverter on the same phase, it just makes things simpler with the relevant authorities.

[SafetyThird]

I would leave your existing FITS system alone, the last thing you want is some minor change invalidating the whole system and losing FITS.

Given all three solutions you are looking at have very similar specs, why not get some quotes for supply and see if there are any major differnces, or whether any supplier proposes something else that you are not aware of.

Yes, I think that's wisest. I've sent off enquiries to 3 suppliers, only ones I could find immediately online supplying the Luxpower. PVPro seem to be the distributor and hopefully they can suggest a local installer

[SafetyThird]

Hmmm, that would require DNO involvement (more than the soft touch permission an AC system would require) and changing my inverter my cause issues with FIT payments. I have 6kw of solar, limited to 3.8kw by the Sunny Boy inverter.

Do you have a 4kW Sunny boy capped to 3.8kW ?, or do you mean 3.68kW. Or is it a later 3.68kW version Sunny Boy ?
In the olden days of FIT you could sometimes get away with a 4kW inverter capped to 3.68kW under the G83 rules, until the DNO's clamped down on that behaviour.

If its a 4kW Sunny boy, even if you've capped it lower you could officially only go with the 3kW battery inverter with the light touch G99 application as the total inverter power would be less than 2 x 3.68kW = 7.36kW.

Replacing the existing sunny boy with a hybrid is generally a no no because of the FITs unless you get complicated with a bi directional generation meter.

If your Sunny Boy is a 3.68kW version I think you could add an additional hybrid with or without extra panels on the same phase and still do the light touch G99 application assuming the hybrid is G100 compliant. The problem is the whole system on the single phase needs to be G100 compliant which it may or may not be depending on how the hybrid behaves.

If I were would I would stick to your plan of an additional AC coupled battery inverter on the same phase, it just makes things simpler with the relevant authorities.

Thanks Nowty, the inverter model is Sunny Boy 3600TL-21 so looks like I misremembered the 3.8 and it's 3.68kw.

So, stick with the AC coupled plan then. Thanks. Leaves the original question, any good/bad reports on the inverters listed. Luxpower is heading the list just on specs currently and I'll see what the supply quotes come back with. ITS have the Solis inverter with 4 x 3000c batteries for £5345 inc vat, so be interested to see what the lux power quotes come to. https://www.itstechnologies.shop/collec ... -2-392-vat

[nowty]

Thanks Nowty, the inverter model is Sunny Boy 3600TL-21 so looks like I misremembered the 3.8 and it's 3.68kw.

Another alternative but unfortunately its pricey and difficult to find a UK installer is a system similar to mine (I did all mine DIY). You also need a Sunny Home Manager 2.0 which adds to the costs.

I say this because you already have a v21 Sunny Boy which is compatible with the Sunny Home Manger and Sunny Islands. The smallest Sunny Island 4.4M has a 3.3kVA grid output so should be compatible with the light tough G99 application and then you have a complete combined system with nice Sunny Portal monitoring and programming via a simple webpage for off peak grid charging.

[Countrypaul]

Thanks Nowty, the inverter model is Sunny Boy 3600TL-21 so looks like I misremembered the 3.8 and it's 3.68kw.

Another alternative but unfortunately its pricey and difficult to find a UK installer is a system similar to mine (I did all mine DIY). You also need a Sunny Home Manager 2.0 which adds to the costs.

I say this because you already have a v21 Sunny Boy which is compatible with the Sunny Home Manger and Sunny Islands. The smallest Sunny Island 4.4M has a 3.3kVA grid output so should be compatible with the light tough G99 application and then you have a complete combined system with nice Sunny Portal monitoring and programming via a simple webpage for off peak grid charging.

If he was to install another PV system in the future (on the barn) would the system allow aother Sunny boy inverter/Sunny Island to be added to the same system and provide upto 7.68kW across the whole system i.e would it provide a simple way to extend the system on the same phase rather than require use of the other phase for the barn. Just thinking of possible future expansion and what might be the most flexible approach?

[SafetyThird]

Just had a look at the sunny island stuff, that’s expensive and needs separate switch gear for ups use and the inverter plus the home manager. Looks to be about £3k before adding batteries. Very nice and well integrated but not cheap.