Combining solar panels of different sizes?

_OS__OS_ Solar Expert Posts: 207 ✭✭✭

I am considering upgrading my system that has one 80W BP Solar panel. A local dealer has Kyocera 85W panels on sale at about one third the price of a new 80W BP Solar panel. My question is: can I combine these two in some way? I will use them together with a SunSaver MPPT charge controller that I have ordered.




  • mike95490mike95490 Solar Expert Posts: 8,970 ✭✭✭✭✭
    Re: Combining solar panels of different sizes?

    If the : Voltage power Max (Vpmax) is not too different, you can parallel them.

    If you place in series, the 85 w panel Amps will be limited to the Amps of the 80W panel.

    The better they are matched, the less loss. Newer panels may have very different voltage/amp specs than old panels, and it may be better to park the old panel at an outbuilding to power a light there.

    VPMAX : 25V Amp =2 50Watt

    VPMAX : 18V Amp=2.7 50watt

    This is a pretty extreme mismatch, and the 25V panel will only output 36W instead of 50, if it was paralleled with the 18V panel
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • _OS__OS_ Solar Expert Posts: 207 ✭✭✭
    Re: Combining solar panels of different sizes?

    The 80W solar panel I have is only one year old and is still in production. Here are the specs:

    Vmp = 17.6V, Imp = 4.5A

    And for the Kyocera I am considering:

    Vmp = 17.6V, Imp = 4.8A

    So this means I can safely parallel them?

  • BB.BB. Super Moderators, Administrators Posts: 30,947 admin
    Re: Combining solar panels of different sizes?

    You can connect them in series or parallel just fine.

    Since you will be connecting them to the SunSaver MPPT--I would probably connect them in series so you can have a single pair of wires home-run back to the controller--instead of two pairs of wires or heavier gauge home run...

    Parallel may give you a bit more power (per data sheet).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Combining solar panels of different sizes?

    series = go with same imp. if not matched go with the lowest imp spec.
    parallel = go with same vmp. if not matched go with the lowest vmp spec.

    do note that if you place them in series that both pvs are limited to 4.5a being the lowest imp of the pvs, so you lose about .3a x 24v = 7.2 watts. paralleled they are a perfect match as both vmps are identical.
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