Mixed Watt panels .

ArneToo
ArneToo Registered Users Posts: 1 ✭
in Solar Beginners Corner #1
Mixed Watt panels into same nppt control. Can you mix 75W and 100W panels
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,663 admin
    #2
    Details matter... Do you have a link to your MPPT controller and manual?

    Also, need to know the Vmp and Imp of both panels...

    In general, for a 12 volt battery bank and "real" MPPT solar charge controller would have the two solar panels placed in series for a Vmp~24 volt array. However, generally we would want the Imp for each panel to be within 5-10% maximum variance (i.e., 5 amps and 5.5 amps)... If the two panels are farther apart, the MPPT controller will not be able to harvest "optimum" energy (i.e., instead of 100+75=175 watts from panels, you may get closer to 75+75=150 Watts or so).

    And, it is possible the lower Imp rated panel could be damaged by the higher Imp panel (i.e., the larger panel tries to put 5 amps through the 3 amp panel...

    I am not sure, but I would doubt that you can mix these two panels in series on an MPPT controller.

    It is possible that you can put the two panels together in parallel (Vmp of the panels are probably in the 17.5 yo 18.0 volt range). They will be OK in parallel (Vmp matches within 5-10% difference)--However, most MPPT controller are less than efficient with Vmp-array less than 20-22 volts or so--And most of these panels are Vmp~17.5 volts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #3
    ArneToo said:
    Mixed Watt panels into same nppt control. Can you mix 75W and 100W panels
    Yes - if all have the same cell count, same Vmp and same (or at least similar) tempco.  Note they all have to be in parallel - you cannot connect them in series if you want to get all available power.  (Actually you can do strings as long as all panels in a string are identical, and the strings fulfill the criteria above.)
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