Can different panels be mixed together?

REPO
REPO Registered Users Posts: 23
I've been searching the NET for days and hours! There are so many different types out there it is confusing. My question is if different brands of panels can be used together in parallel?

Can a 17.5V panel be in parallel with a 30.1 volt panel? (MPPT controller)

Can a Uni-Solar panel be used with a standard glass panel? (parallel)

Can a 230 watt panel be put in series with a 100 watt panel?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Can different panels be mixed together?
    REPO wrote: »
    • Can a 17.5V panel be in parallel with a 30.1 volt panel? (MPPT controller) NO
    • Can a Uni-Solar panel be used with a standard glass panel? (parallel) Depends
    • Can a 230 watt panel be put in series with a 100 watt panel? Depends

    Basically, the answer is of two types... Functional and efficient.

    The efficient answer is that you should match Vmp to within 10% for parallel connections and Imp within 10% for series connections.

    I.e.:
    • 17.0 volts in parallel with 18.4 volts (or less)
    • 8 amps in series with 7.2 amps (or less difference)
    Functional, you can put a 17.5 Vmp panel in parallel with a 32 Vmp panel and it will work.

    But, an MPPT controller may not maximize the power output and a PWM panel will simply set Vmp of the system to ~16 volts or so--Meaning that 1/2 the output power of the higher voltage panel is lost.

    With arrays, can put two 17.5 Vmp panels in series and then put them in parallel with a third 35 Vmp panel.

    And other rules too... Many older/smaller panels are rated to around 70VDC maximum. While newer/larger panels are rated for 600-1,000 VDC. So you should not put a bunch of small 70 VDC panels in series for a 100-150 VDC array for a large MPPT type controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • REPO
    REPO Registered Users Posts: 23
    Re: Can different panels be mixed together?

    Awesome! Makes sense, but I though I should ask.

    I will stick with matching panels were possible. The reason I asked about the Uni's is that they look like they would fit in some of the tight areas on the RV roof, as well, they seem to be designed so as shaded areas will not shut off the entire panel. I think that would be great, as up here in Canada, most places we go have lots of trees, so at some point or another during the day, there is going to be some shaded parts.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Can different panels be mixed together?

    In the end, shade is bad news for Solar PV panels--Pretty much assume 50% or more loss of power with any visible shading.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • REPO
    REPO Registered Users Posts: 23
    Re: Can different panels be mixed together?

    I just looked at those Uni's again. They are rated at 16.5 Vmpp, and I belive many of the 100-120 watt glass panels are around the 17.5 volt range. If I understand correctly, they would be able to work together fine, as the voltages are within 10% of each other. (parallel system)

    Correct?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Can different panels be mixed together?

    Yes, they will work fine.

    Note that 16.5 Vmp on a hot day with a cold battery bank does not leave much head room left between Vmp-array>Vbatt-charging voltages. (equalizing a battery bank is around 15-15.5 volts or so, and on hot days, the Vmp can drop by 10-20% which will reduce charging current into the battery bank).

    Adding the Vmp=17.5 volt panels in parallel makes things better in any case.

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