3.8kw Offgrid: Victron EasySolar 2 48v.35 with mppt 250/70 3000w Design + Fuses

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Andrew asked Oct 1, '22

3.8kw Offgrid: Victron EasySolar 2 48v.35 with mppt 250/70 3000w Design + Fuses

Is the below correct before I go further? Thanks in-advance

PV 3.8kw Offgrid: Victron EasySolar 2 48v.35 with mppt 250/70 3000w

Panels = 10 x JA SOLAR JM60S20 380/MR 380W VOC 41.62 V VMP 34.77 V ISC 11.47 A MP 10.93 A CLASS II MAX SYS 1000V, MAX AMP 20 TOTAL 3,8KW
two strings 5 x 2 in series and wired series parallel, only one mppt and costly for another so all panels same direction height etc.PV Wiring = 6mm x 10m to inverter from shortest end 17m from last panel. 2 shocty diodes inline on each string + 1000v/20a to prevent reverse polarity. Then 32a 1000v disconnect before going to inverter
Storage Pylontech 3000 and 3000c with 2m pylontech victron cables of correct size with 2 x 120a fuses on each pole.
AC As this is not mains connected I am wondering what sort of consumer unit as have a few given to me but only need one ring main - .2 at the most for garden tools, But note easysolar has 2 ac outputs, does this mean no consumer unit is needed?

Does this configuration sound ok?

Pylontech EasySolar All-in-One fuses system design

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marekp answered · Oct 03, 2022 at 11:30 AM

@Andrew

Ad. 1&2 Panel setup looks good for MPPT 250/70

Make sure that plus and minus lines from panels a run close to each other to eliminate in induction loop.

You can use four pole fuse, 2 pole in each single string (16A), and than connect them together.

If two pole is used the fuse at the output from panels should be more than sum of currents in two parallel strings (more than 2x11.47A) 30A should be OK.

Ad. 3 I do not think you need fuse on each pol of the battery. On "plus" should be sufficient. If Pylotech say one on each pole it is OK too with little extra voltage drop on the second fuse.

Ad. 4 You need consumer unit at the output from ES-II because you need breakers for AC-out1 and AC-out2 (if used). Also RCD is needed for loads.

screen-shot-2022-10-03-at-12006-pm.png (176.7 KiB)

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Andrew commented · Oct 03, 2022 at 01:13 PM

thanks again @MarekP it is perhaps the software pic output but to confirm, I have just the one mppt which is inbuilt with the EasySolar 2 gx incase I didnt mention it

- So do you think it makes much difference where cables combine from two strings?

I have enough cable for 4 poles but just wondering if after diodes why it cannot just go to branch connectors or Y cables then to one 32a x 2 pole surge protection. Otherwise suspect i need another surge protector on each string.

The person/very small company I got inverter from said I needed the 2 fuses for each pole of the battery but what you say makes perfect sense but does it impede on the - pole if using on each?

Kind regards, A

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marekp Andrew commented · Oct 03, 2022 at 01:58 PM

@Andrew

it is perhaps the software pic output but to confirm, I have just the one mppt which is inbuilt with the EasySolar 2 gx incase I didnt mention it

The pict is from Victron MPPT calculator that I used to confirm that the setup of the strings (5x2) is OK for MPPT 250/70 that you have inside the ES-II.

- So do you think it makes much difference where cables  combine  from two strings? 
I have enough cable for 4 poles but just wondering if after diodes why it cannot just go to branch connectors or Y cables then to one 32a x 2 pole surge protection. Otherwise suspect i need another surge protector on each string.

I heard two opinions on that.

1. each string in the parallel setup should have its own fuse.

2. you can have one fuse, but double size (A) after connecting strings.

I guess the first is better because when one fuse is burnt you only loose half of the power from PV.

The person/very small company I got inverter from said I needed the 2 fuses for each pole of the battery but what you say makes perfect sense but does it impede on the - pole if using on each?

Two fuses should not impede the battery operation. Resistance of the fuse is very small.

If by using only one fuse, you may loose warranty from the manufacturer, I would install two.

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Andrew commented · Oct 23, 2022 at 12:34 PM

@MarekP re consumer unit, i was wondering what amperage the a/c should be as the manual doesnt state it mppt manual is subjective. Many household are 100a, shed type ones 40a. The Easysolar datasheet makes me think 35 or 32 as in the model number but confused due to the high amp of batteries. Got lots of din rail One 4 pole RCCB 63a.30ma, then quite a few of varying amp breakers B10, B6, B16, B6, B32.

I dont know if i am over thinking this, just need to power 2 freezers, power tools charging and some lights 600w constant,but can switch to the mains ring circuit if needed.

But with a 6.2kwa (east west facing) hybrid and the one in question (off-grid south facing) I am at 10kw pv and have approx 27kw/h batteries, so was going to trial this year to see if possible to be grid free of electric. I suspect a generator will be needed.

Am just itching to put the 3kw system on as now have all of the dc side ready except the curve ball of the 3 panels which are 370w as opposed to being JA solar. I thought best to go on one string with 2 ja380w, keeping the 5 ja 380w on the other string. Any thoughts greatly appreciated.

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marekp Andrew commented · Oct 23, 2022 at 12:56 PM

If all loads are behind ES-II the max AC current is 32A.

Max constant power at 20C going to loads is 2400W.

35A is a max charge current on the DC side.

Additional 70A DC charge current can come from MPPT 250/70 but it will not produce more than 4kW from your PV panels.

Currents on DC side have no bearing on AC max current.

As for the PV array, I would make string as symmetrical as possible (3+2 and 4+1). Add those diodes and it should work.

Those diodes are good idea any way if you have any shading.

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Modifications Space

Node Red Space

Answer 1 · 2022-10-23T08:03:53Z

Andrew answered · Oct 23, 2022 at 08:03 AM

@MarekP I just noticed 3 panels although looked the same are from my previous house and thought they were the same until mounted them. I have 10 panels in a row and was doing 2 strings of 5 in series wired series parallel. The 3 different ones are longi 370w compared to the JA solar. Do you think I am still ok with the same setup and easysolar with the built in mppt?

the difference to the above is:

Efficiency: 19.8%
Peak power W_p: 370W
Voltage at peak power: V_mp: 34.4V
Max open circuit voltage V_oc: 40.9V
Current at peak power: 10.76A
Max short circuit current I_sc: 11.52A
Weight: 19.5 kg
Dimensions: 1775 x 1038 x 35mm

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marekp commented · Oct 23, 2022 at 08:27 AM

It is not ideal situation but it could work.

You will have to install a diode in series to prevent the one string from feeding another when string voltages are different.

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mppt-shematic.jpg (79.5 KiB)

klim8skeptic ♦ marekp commented · Oct 23, 2022 at 01:27 PM

You will have to install a diode in series to prevent the one string from feeding another when string voltages are different

The "series fuse rating" is what you should be looking at for your panel.

You can dump all available energy from 1 string, into another damaged/shorted string without exceeding the panels "series fuse rating".

The "series fuse rating" refers to the current a panel can withstand before damage will occur.

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Answer 2 · 2023-01-10T08:57:43Z

Andrew answered · Jan 10, 2023 at 08:57 AM

@MarekP Hi Marek, I have the system ready but thought I would return to you response. Do you mean the single MPPT 250/70 will be OK or do I need one for each string?

thanks, Andrew

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marekp commented · Jan 14, 2023 at 11:57 AM

If your configuration and number of panels did not change (two strings of 5 connected in parallel, 3800Wp total), one 250/70 is enough.

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