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Inquiry and explanation


Namzy
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Good day. Pls help what's the best pv array config for max 75v and 25A and cable size for distance about 15 to 20m
And now other question why will a manufacturer stated max power of mppt in watts and still state max open circuit voltage it can withstand and max charge in amps. For example for above the oem axpert Mks 3kva states máx 600W for 75v and 25a shouldn't it be 75vx 25a=1875 watts?

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24 minutes ago, Namzy said:

Mks 3kva states máx 600W for 75v and 25a shouldn't it be 75vx 25a=1875 watts?

Hi Namzy, from the detail below, the 25amp rating is the max battery charging amps, Its not related to the current limitation on the PV input. 

You can effectively only connect 2 x 300 watt panels in parallel to max your system out. 

MKS.thumb.JPG.1a9b8415ec594efbd4c2e0bc4a307461.JPG

 

 

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1 hour ago, Jaco de Jongh said:

Hi Namzy, from the detail below, the 25amp rating is the max battery charging amps, Its not related to the current limitation on the PV input. 

You can effectively only connect 2 x 300 watt panels in parallel to max your system out. 

MKS.thumb.JPG.1a9b8415ec594efbd4c2e0bc4a307461.JPG

 

 

Thanks for answering but Can't I for example connect 4 200w in 2x2 with total max v at 72 and max total amp at 11.12a

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2 minutes ago, Namzy said:

Thanks for answering but Can't I for example connect 4 200w in 2x2 with total max v at 72 and max total amp at 11.12a

I guess you can, but you will be over sizing your array with 200Watt. I can not guarantee that you wont hurt your MPPT?

I am still old school and prefer to size the array according to spec. Personally don't like taking risks with my equipment. 

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17 minutes ago, Namzy said:

Someone on this forum states that he has successfully connected 750w to the same inverter without issues for long

You can try it, but please not on my recommendation. I dont want to be held responsible for any damage to your inverter.

I would rather stick to the rating, add a Victrom MPPt to your system and add some more panels to the MPPT, expanding your PV that way. 

Some MPPTs will limit the current, so even if you add 750 watt is will only allow through 600 watts if it was rated for 600 watt. Some cheaper MPPT's rely on the PV array size to limit the current through it. These cheaper MPPT's will blow when PV array is to big. 

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32 minutes ago, Namzy said:

Axpert themselves recommends installing a 25a dc circuit breaker between pv panels and inverter which I'll do.

To move 11.12 amps at 72 volts over 20 meter and remain below 3% volt drop you will need to use a 6 square mm wire. But if you plan to upgrade in the future, lay a bigger cable to allow for expansion. 

  

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