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Good day 

I would like to know what batteries to connect to my system

I bought 3 x 5kva 5000w MKS inverters and 27  x 325wp Panels 

I do not have sufficient space on my roof and is also not facing north and decided to put my panels on stands to follow the sun east to west 

with a sun tracker. 

my average useage is about 3000 units Kwh per month 

I do have 3 phase supply thus the reason for 3 x  5kw units  I do not need 3 phase as all my equipment is single phase 

I reason to have 1 inverter per phase to eliminate the possibility of being with out power at all when one phase from municipality is down 

Your advice / comment will be appreciated.

take care 

Eugene  

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Hi Eugene, Welcome ..

lately Pylontech's are becoming very popular and your inveter is approved for use with the Pylontech's. It is basically maintenance free compared to lead acid, a bit more expensive , but offers a lot more usable storage than Lead Acids. 

There is a post about them, you can find it Here.

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Welcome Eugene,

Question: Why do you need batteries?

Options now are to grid tie, depending on where you are, which is much cheaper and requires no batteries.

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13 minutes ago, EugeneF said:

will this work for me

It depends on what your exact needs are. 

What I know about Axpert is that they can not operate without batteries. Then it has a limitation. It will switch between grid mode and battery mode depending on your settings to try and match the demand. If your batteries goes below a certain value it will switch back to grid for example and above a certain value it will switch back to battery mode.

A hybrid will constantly mix PV , battery and grid to match the load. If your load is 2kw and the panels only supply 1kw, the hybrid inverter will "mix" in the 1kw shortage from Grid, or your batteries to meet the demand. Hybrid is better in my opinion. 

Then there is the legal part that has surfaced lately where some counsels dont allow Axperts to be connected to the Grid. 

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23 minutes ago, EugeneF said:

How ill I need to configure my panels on this

3 in series with 3 in parallel  as I have 27 panels that was sold to me  That is 9 per inverter

If they are 60 cell panels then 3x3 is great. If they 72 cell panels then one needs to be more circumspect. Three 72 cell panels in series can have a Voc max of greater than 145VDC which is the upper limit of the Axpert's MPPT.

Try using  the spreadsheet I designed a while back and adjust temperature and string and panel data as see what your results are. The colder it gets the more efficient panels are and voltage over the string will increase. 

https://powerforum.co.za/topic/1590-pv-array-sizing-tool/

 

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20 minutes ago, EugeneF said:

3 in series with 3 in parallel  as I have 27 panels that was sold to me  That is 9 per inverter

Please check on the voc rating of your panels, it should be in the region of 47 volts per panel. The general feeling on the forum is that 3 x 47 = 141 volts  will be to close to the max VOC rating of your inverters. 2 in series, then 5 strings in parallel will be safer, but then you will need 3 more panels. 

EDIT: Sorry was answering on at the same time as Chris. So this is basically a duplication of his answer. 

From the info below, you should be fine with 10 panels per MPPT. 

246.JPG.62875f05bfaa9e92fb76ac5c11a097bf.JPG

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1 minute ago, EugeneF said:

My panels are 72 cells  Voc 45.5  Canadian solar

That is pretty close to max VOC. Should you be in Grid mode and you experience cloud edge effect, you will exceed the max VOC of the units. 

No guarantee it will damage your system, but it is risky. Going for 2 in series will leave you with enough voltage to charge your 48volt bank. 

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35 minutes ago, EugeneF said:

2 in series and 5 strings it will be  Thank you jaco

FWIW, depending on the distance from panels to MPPT, it may be prudent to check the cable losses, which can be mitigated by 6mm or 10mm cables.

Me, I'm in the process of contemplating to take out the non-new-standard cables and replacing them with 10mm2 regulatory cable.

Jip, the cables now have regulations that ones must adhere to.

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30 minutes ago, The Terrible Triplett said:

FWIW, depending on the distance from panels to MPPT, it may be prudent to check the cable losses, which can be mitigated by 6mm or 10mm cables.

Should your Voltage under load drop to 65 Volt and you draw the full 3250 watts available from your array (prepare for 80% of that), you can use a 25 mm cable over a 20 meter distance and still be within the recommended 3% volt drop. 

If it is a shorter distance from your combiner box to your MPPT's then we can recalculate the cable size. 

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6 minutes ago, Jaco de Jongh said:

Can you please share this regulations? 

Let me see what I can find out as 3 sparkies told me this, after being on a course for solar panel CoC's.

The where quite vague, got a hint of an idea to get an impression that they rather supply and install ... so I did not push them at the time for the exact details. They KNEW I could get it at cost. ;-) 

Time has now arrived, as I need to buy some.

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2 minutes ago, The Terrible Triplett said:

Let me see what I can find out as 3 sparkies told me this, after being on a course for solar panel CoC's.

Thats is awesome news, please sommer find out where one can do that course. I would love to attend, even if I have to take a trip to Cape Town. Then at least we will all know what is really expected for them to issue a COC. 

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