Adding on or new controller needed too?

Ralph Day
Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Hi all
I'm thinking about adding some more pv, pointing west to give some more power in the late afternoon/evening for heat pump operation. My MX60 has 2.1kw presently with the max ever seen of 2300 watts (cold and edge of cloud happening). So I still have about 20 amps of capacity left on the MX60. Battery voltage 48vdc nominal.

Present panels are Sharp 72 cell 180 (2 panels) and 175 watt (10 panels).

NT 180 U1
180 watt
44.v open circ voltage (voc)
5.6amp short circuit current (Isc)

NT-R5E1U
175 watt
44.4v Voc
5.5amp Isc

I have access to some Sharp 200 watt panels (60 cells), but wonder about their compatibility if I try to add them to my MX60 controller.

ND 200U1F
36v Voc
28.42 Vpm (Max power voltage)
7.9 Isc

The 12 present panels are in 2x series parallel. Can I add a combiner/breaker/cabling to add the output of the 200 watt panels, or should I just plan on a separate charge controller for any I purchase and install?

Thanks

Ralph
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Adding on or new controller needed too?

    Probably would be better to look at a second charge controller for those new panels. The Vmp/Imp ratings are too far apart (over 10% difference) that you cannot easily series or parallel these panels.

    For a 48 volt battery bank, the ND 200U1F should be three in series minimum. Two will not cut it.

    And you need to check the Varray-in max voltage for the charge controller--In a very cold climate, the three panels in series may exceed the Vinput rating for many high end MPPT controllers (it is close).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #3
    Re: Adding on or new controller needed too?

    Thanks Bill
    Since they would be pointing due west and only really for afternoon/evening harvest, would a pwm controller do just as well? Or are their Varray max values lower than MPPT controllers? My only experience is with the MX60

    Ralph
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Adding on or new controller needed too?

    No--PWM controllers will not cut it (efficiency wise)... For 48 volt battery bank, you should be looking at a ~70-76 Vmp array.

    Your approximatly 87 volt Vmp array would be (roughly):

    70v/87V = 0.80 - ~80% as efficient vs running on a MPPT controller (may be "good enough" for your needs).

    They will work on a C40 type Schneider/Xantrex controller--Possibly.

    Basically the typical "high end" controller will take ~140-150 VDC max.

    The Midnite Classics will take higher voltages:

    http://www.solar-electric.com/misoclchco.html

    And there are a couple MPPT controllers that will take Vmp in the range of 400 VDC maximum (Schneider and MorningStar).

    But these are not cheap.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #5
    Re: Adding on or new controller needed too?

    So now the quest becomes: find some panels that "fit" with my present ones at the price point of the 200watt units, or, for the same money the 200watt units and another controller. Have to do some on-line shopping.


    ralph
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