Bit of help needed with calculations, new system. (basic stuff)

[torbrowser]

Hi all,
About to start installing my Hybrid PV system on my house, i have many questions but i will work through them one at a time to try and keep things as simple as i can.

System
Growatt 6000w Hybrid inverter 2 x strings
16 x 385w Panels (2 x 8 panel strings)
2 x 3300w batteries.

Firstly i have been doing the calculations on the string size, here are my workings out.
8 x 385w = 3080w

O/C volt @ 25 deg C 40.6V x 8 = 324V
O/C volt @ 0 deg C (co-eff V oc = -0.25%) 324V x 0.25% = 0.81V x 25 = 344V per string

My Inverter is rated at,
6000w
550v d.c
Max input current 16.9 d.c A*2

What is not clear to me after reading the booklet, is the max voltage 550v per string
And what does the A * 2 mean after the input current.

Kind regards
Jack

 

[torbrowser]

Next one,
I have bought all this stuff as a kit from my supplier.
Connecting my lithium batteries,
I have 2 x Growatt 3300w batteries, these will connect in parallel, and would require an isolator or possibly breaker between them and the inverter.
Instructions are quite poor IMO and only shows batteries connecting to a junction box, the current will be high at 3300w / 51.2v = 64.4 A per battery this will require some serious isolator switches.

What is the best practice in this regard.

Kind regards
Jack.

 

[johnb2713]

And what does the A * 2 mean after the input current.

Kind regards
Jack

Each string I.e. each of the inputs is rated the same 16.9amps

 

[torbrowser]

Thanks,
Am i correct in assuming voltage and power rating of the inverter, 550v / 6000w is the total value of both strings ?

 

[torbrowser]

I will simplify my question.
My inverter is rated at 550v and has 2 string inputs.
I want to install 2 x strings of 324.8v open circuit each.

Is the rating of 550v per string ?

 

[johnb2713]

Yes

 

[torbrowser]

Thanks again.

This system came as a kit as stated, so one would assume it is correct, i want to understand WHY it is correct, hence daft questions.

Next daft question.

Do i need to put a breaker or isolator between the batteries and inverter, looking at other installations its mostly not done, being a simple sparky i think its a good idea.
I have 2 x batteries at 3.3kW parallel 6.6kW
Voltage rated at Nom 51.2v gives a rating of 64 A per battery, and not being used to dealing with DC seems a big number.

What is best practice and what is common practice.

Kind regards
Jack.

 

[binky]

battery leads should be fused with something like this https://www.waxmanbatterystorage.co...olator-fuse-switch-disconnector-size-00-body/

 

[torbrowser]

Thanks,

Am looking into these, will find out what fuse type comes with the unit, i have found a specific DC quick blow NH fuse is available.

 

[torbrowser]

Also, what are we fusing against, the load break isolator and the short circuit protection i get, but does this protect the battery or the cabling.

Reason for this is the proposed layout of my system where the battery isolator is going to be outside the fireproof cupboard, so short circuit protection will only be down stream of the battery between the fuse link and inverter terminals, overload is unlikely as its limited by the consumption of the inverter.

Seems to be a grey area. (to me)

Kindly educate me.

 

[Ucatchmydrift]

I bought the 200amp version of this for inbetween the inverter and battery. (high amp dc breakers are seemingly hard to find.). I have not got an isolator yet. My inverter manual states what ampage the breaker should be. Manual also states using 35mm2 battery cable, im going for 70mm2 as i have some already.

https://www.ebay.co.uk/itm/19523832...sv1MPSPSK-&var=&widget_ver=artemis&media=COPY

 

[yozhughes170]

I have the same system with 5 more panels and this was ‘professionally’ installed with no fuse or breaker between batteries and inverter, the sph6000 has a dc isolator built in and the Growatt batteries have a on/off switch

 

[johnb2713]

I have the same system with 5 more panels and this was ‘professionally’ installed with no fuse or breaker between batteries and inverter, the sph6000 has a dc isolator built in and the Growatt batteries have a on/off switch

That could get quite interesting.

 

[torbrowser]

I have the same system with 5 more panels and this was ‘professionally’ installed with no fuse or breaker between batteries and inverter, the sph6000 has a dc isolator built in and the Growatt batteries have a on/off switch

Do you have the same batteries, ML33 RTA ?

How do you rate it? I have just got mine online, i can't understand the setting menu or instruction book as they are (badly) translated from Chinese. the inverter seems to have a mind of its own.

Anyone on here know these inverters for some advice ?

 

[yozhughes170]

Ye been through all that, the inverter will randomly import/export 0.02-0.03Kw. The settings you’re going to need are best done from a pc you get a better idea of what to change if you’re planning on charging your batteries at a specific time. Yes I have the same batteries they’ve done as asked although I’ve just ordered a 3rd for winter use as I have a EV and work shifts. Also because I’ve exported over 40% of my solar energy I’ve swapped my EV charger for a zappi and just installed a Eddi for my immersion heater so no longer exporting on sunny days. I’m also with octopus on the Go tariff

 

[torbrowser]

OK, thanks, maybe we can help each other.
How have you connected to your PC, do you have the shine device plugged into it?
I have this on order, unless you know a better way.