Matching Solar Panels

54d18
54d18 Solar Expert Posts: 81 ✭✭✭
in General Solar Power Topics #1
I have a system with 2 75w siemens panels in series, connected in parrallel
with 2 175w sharp panels for a total of 490w. The MPV are 17v on the 75's
and 34.5 on the 175's. My present controller is a Rogue 30A, I am looking
to upgrade to the Midnite Solar Classic 150 and also add more panels but
I am not seeing any panels at a good price with 34v MPV, if I go to 30v MPV
how much loss will there be, would it really be a big deal?

T
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Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
    Re: Matching Solar Panels

    what about more '12 volt' nominal panels? in series you will get a good match on the Vmp
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Matching Solar Panels

    Yes, it's a problem. It seems the "true" 12 and 24 Volt panels are vanishing. I have four of those Sharp 175's with Vmp 35.

    If you put panels with a Vmp of 30 in parallel with those with a Vmp of 35 you'll pretty much be wasting your money. The higher Voltage panels will "pull the array Voltage up", meaning the low panels will be operating in the Voc range. At those Voltages the panels are not "loaded" properly and thus won't put out full current. Depending on the exact conditions (Voltage difference, Imp rating, insolation, temperature, et cetera) this is either a small power loss for the lower Voltage panels or a fairly significant one.

    It may be more feasible to keep the array as is, and since your planning on buying a new controller anyway simply apply the new panels in a workable configuration on that.
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  • 54d18
    54d18 Solar Expert Posts: 81 ✭✭✭
    #4
    Re: Matching Solar Panels

    Does anyone know of a comparitively priced panel with a vmp of 35v?
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #5
    Re: Matching Solar Panels

    54.. T,

    Astroenergy has some Poly modules that have Vmps of 35.08-35.66, in the range of 275-290 Watts STC. They have been inexpensive to my way of thinking. Poke around on the Net. N AZ W&S used to carry some of these. YMMV Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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