Wize size MPPT and Voltage on PV Side

KhellSk
KhellSk Registered Users Posts: 91 ✭✭
edited December 2023 in Solar Beginners Corner #1
Hi again everyone. This is going to be simple for but thanks in advance

Array is 3 series x 3 parallel
48w
3.02 A SCC 3.4
15.9 VOC 19.8

Bank 12v

In all the times I spent reading about MPPT wire sizing, it was my understanding that one of the perks of using MPPT controller is because it allows you to raise voltage to travel further. Well I just got my first mppt and the VOC is what it should be but when I plug in the controller its lowered to Bank charging voltages. Which I would expect on the bank side but didnt expect on the pv side.

So was I understanding wrong when I expected voltage to be close to 47v or is something wrong with the controller ?

To be noted I havent seen the controller work full sun yet. We have been having lots of Full cloud days.

_____________________________________________
[3p3s 48w 15.9Vmp] [Flooded 2x 6v 150ah]
[Victron 50/100 700wMax MPPT]







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Comments

  • BryceFreeman
    BryceFreeman Registered Users Posts: 27 ✭✭
    #2
    Yes, the volt should be close to Vmp*3. But I suggest you check the MPPT again when it works in full sun as sunlight will significantly affect the panels performance. The reading may be inaccurate because of full cloud days.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #3
    What is the brand/model of MPPT controller (link is OK).

    What are the Vpanel and Ipanel numbers? What was the sun like (full sun, winter overcast, etc.)?

    You are correct, in general, the Vmp-array should be around 3 series * Vmp-panel (or down towards 80% of Vmp-array-spec-sheet on hot/sunny days).

    That the Varray fell to battery voltage is not a good sign. The Vpanel voltage could rise to 3*Voc (3 series) if the battery is fully charged and the controller is not drawing any power from the array (full battery)... When you say the Vpanel was Voc (was this closer to 60 volts, or 20 volts)?

    As always, the questions from the peanut gallery--Is the array wired as 3p*3s?

    Also, when getting a solar charge controller going--Always connect the battery bank to the controller first (this allows controller to "boot" and figure out the bank voltage is 12/24/48 volts). If you connect the solar array first, then the battery bank--The controller can make a mistake and choose the wrong bank voltage, boot in an unstable configuration, or even possibly damage the charge controller (never connect a solar array in sunlight to a charge controller first, then the battery bank--And always disconnect solar first, before disconnecting the battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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