question

gilles avatar image
gilles asked

solar array config

Hi,

I have 4 x 40 w victron (18.3v/ 2.2 A) panels plus one 100w Energie mobil (17.4v/5.8A) solarpanel on the roof of my Rv. I need to connect all that to an mppt 75/15 wired to a 250ah 12v lihitum battery.

I am wondering what would be the best configuration for it. i have also a spare mppt 75/15.

I tought about doing like this : 2 x 40 w in series wired together in parallel with an another 2x 40w couple .So it will be 2 couples on one mppt giving in 160 w /36v/4.4 A

And the 100w panel alone on the other mppt on .


I think this option might be the best for optimal efficiency ?

solar
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2 Answers
wkirby avatar image
wkirby answered ·

The configuration that you suggest would work well for the 4x 40W panels.
The 100W panel would work on it's own controller, but it's Voltage is pretty close to the battery Voltage which would reach 14.8V when full. The MPPT needs 5V above battery Voltage to start up and the 1V above battery Voltage to run. You might not get the full power from this panel at times if its Vmpp below battery Voltage + 1V.

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gilles avatar image gilles commented ·
Ok. So ,there is nothing we can do about it ? or i would need a new panel with higher Vmp around 27v. when you say not the full power , you mean like 50percent of its power ?thanx
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wkirby avatar image wkirby ♦♦ gilles commented ·
How much power it makes would depend upon the conditions. On a sunny day it might make the full 100W.

Either a panel with a higher Voc or if you have space, another one the same in series with it.

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ahtrimble avatar image
ahtrimble answered ·

I think the 2 strings of 2 Victrons each is the way to go.

Honestly, the Energie is probably not worth installing due to its low voltage output vs the needed voltage to actually charge the battery.

Another thought, if you can get another PV that is close to the Energie specs then wire it in series with the one you have for the added voltage and put it on the second MPPT.

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