Solis 3kW AC coupled Inverter & Fogstar 5.12kWh Rack Battery ?

[Oldman22]

I have a 2014 FiT solar system which is working well but dumping up to 2/3rds of its generation even at this time of year back to the grid, I would like to make use of at least some of that so I need battery storage.

Having followed several big builds on here & other forums I was champing at the bit to get started, but the costs didn't weigh up & I have come to the conclusion that a big build is not viable for me, the costs keep mounting & considering I'm not a huge kw user the payback gets too long.

But my attention was drawn to a simple solution that would have a very short payback (under 3yrs) for my situation.
One or 2 of these https://www.fogstar.co.uk/products/server-rack-battery-48v-5-12kwh? connected to one of these https://www.itstechnologies.shop/pr...-storage-ac-coupled-battery-charger-inverter? with a wifi stick https://www.itstechnologies.shop/products/solis-data-logging-stick-wifi-gen-3

That comes in at £2162 with 1 battery pack or £3512 with 2 battery packs.
OK the inverter is 3kw only but will more than take the edge off my grid demand & I will soon know if the 2nd battery is needed. Adding that is easy.
Ive not heard bad things about Solis inverters, the fogstar rack batteries seem to be a new line, I cant find any user reviews yet online so maybe the March 1st dispatch are the first ones?

A couple of isolators and 2mtr of cable and I'm done I think. Will they play nice together??

Now the only flaw in this plan is if I draw more than 3kw on a cloudy day or evening I'm going to spike & take from the grid and will it annoy me so much I will wish I had gone for a 5kw inverter? Who knows but with short payback I think I will take the risk.
The price difference between 3kw & 5kw AC coupled inverters is almost double, makes me think adding a second 3kw Solis inverter plus battery in future wouldnt be such a stupid upgrade. 2 x 3kw inverters costs near the same as one 5kw inverter, plus if they will play together if one were to fail down the line, not all your eggs are in one basket.

Comments...

 

[johnb2713]

That all looks good apart from one slight caveat.... The inverter spec says for it's rated output "3kW (Requires battery voltage higher than 55 V)" and the Fogstar battery has a Nominal Voltage: 51.2V. I dont know what effect this may have on the inverter and it's output.

 

[Oldman22]

John, inverter data sheet says rated battery voltage 48v but next line down says voltage range 40-60v
From the manual:

So It seems to fit the bill.
Seems what they are saying I guess is to achieve full 3kW output the battery voltage must be over 55v? Re reading it, looks to me that's only for UPS type output (back up)

 

[johnb2713]

I dont know, I have no experience of this inverter.

The datasheet says:-

 

[Oldman22]

For clarity.

 

[binky]

I suspect it's not an issue, but I would put the question to ITS and/or Solis technical helpline just to double check.

 

[johnb2713]

I suspect it's not an issue, but I would put the question to ITS and/or Solis technical helpline just to double check.

I suppose it depends whether it reduces it's max output or trips on low voltage?

 

[Oldman22]

As this issue or not revolves around the AC backup spec which is a separate AC output for use when the grid is not available, I wont worry as I have no intention of using that output.
I have emailed Solis on that point and also asking if two can co exist in the same installation. I wont hold my breath though

 

[binky]

I suppose it depends whether it reduces it's max output or trips on low voltage?

I got the impression that it affects the max output rather than stops working, but I've not installed a solis with less than 3 pylontech 2000 batteries. I'll have a look at the spec of those batteries, it may offer a clue.

 

[michael8554]

"if I draw more than 3kw on a cloudy day or evening I'm going to spike & take from the grid and will it annoy me so much I will wish I had gone for a 5kw inverter?"
Kettle + Toaster
Oven + Hob
Dishwasher + Washing Machine
Immersion heater + household load
Hot Tub, swimming pool heater, sauna ?

 

[Oldman22]

You cant frighten me
Kettle is 2.5kw and I hid the toaster.
Oven is banned since I bought a Ninja 15 in 1
Hob is gas
Dishwasher was new 10yrs ago and still is as she used it 5 times total
No immersion & household background is 2-300watts
Hot tub used to be a galvanized bath filled from a kettle in front of the coal fire & the dirtiest got last use.

 

[Chrisbee]

Now the only flaw in this plan is if I draw more than 3kw on a cloudy day or evening I'm going to spike & take from the grid and will it annoy me so much I will wish I had gone for a 5kw inverter?

Think of it as intended to put a big dent in your draw from the grid rather than eliminate it all together.
If you only use the batteries to mop up unused solar energy, then some days the batteries won't have charged as much as you need either, so you'll draw from the grid once they're empty anyway.

 

[johnb2713]

Think of it as intended to put a big dent in your draw from the grid rather than eliminate it all together.

Better to think of it a little more invested in the inverter saves all of the peak rate draw from the grid, speculate to accumulate!

 

[bladerunnerpv]

w.r.t Fogstar ESR51.2V 5.12KWH Rack Battery
80% DoD on 5.12kWh is 4.096kWh usable
very nice to see the fogstar is heated above 5degC
the round-trip efficiency would be nice to know, assume 95%
£1350 (+VAT??)

Presume the BMS will be firmware/software upgradeable to account for new inverters reaching the market


compare Pylon 4.8kWh US5000, from their sepc
95% DoD on 4.8kWh is 4.56kWh usable, whether 95% reduces the life I don't know
not heated IIRC
£1340 +VAT

Also in bundles
15kWh bundle £3999.99, includes cabinet it would appear
https://www.fogstar.co.uk/products/...24859&pr_ref_pid=7082856087611&pr_seq=uniform
30kWh bundle £7999.99, includes cabinet it would appear
https://www.fogstar.co.uk/products/...55867&pr_ref_pid=7091563724859&pr_seq=uniform

 

[Oldman22]

£1,349.99 delivered, I just purchased one, shipping tomorrow 48kg on a palletised delivery.
I better go buy an inverter now

 

[bladerunnerpv]

£1,349.99 delivered, I just purchased one, shipping tomorrow 48kg on a palletised delivery.
I better go buy an inverter now

Free delivery too!
Was that including or excluding vat ?

Look fwd to hearing how you get on with them

 

[Oldman22]

Free delivery too!
Was that including or excluding vat ?

Look fwd to hearing how you get on with them

£1,349.99 Including VAT delivered free.

The server rack and 3 batteries would have been the deal to go for if you needed that capacity as the rack is being given free at the moment with 3 batteries purchased.

 

[Ronski]

Subbed to the thread, as it was me that suggested this setup, keep us updated as to how you get on.

Did you get in touch with the electrician I suggested?

Regarding the voltage, the guy in Sandwich is using Pylontech and they are the same voltage range as the Fogstar pack.

 

[Oldman22]

Hi Ron I didn't go to the sparks, thought I could manage a self install.
I spoke to Fogstar and they tell me they have tested the batteries perform fine with Solis inverters and it comes with the quickstart setup if needed.
So I shall find out wont I
Just need to get the inverter ordered now.

 

[johnb2713]

Hi Ron I didn't go to the sparks, thought I could manage a self install.
I spoke to Fogstar and they tell me they have tested the batteries perform fine with Solis inverters and it comes with the quickstart setup if needed.
So I shall find out wont I
Just need to get the inverter ordered now.

Don't forget, plenty of photographs of your handiwork.