low voltage vs high voltage solar panels

rollandelliott
rollandelliott Solar Expert Posts: 834 ✭✭
in Solar Beginners Corner #1
I see certain companies designate their panels as either being high voltage or low voltage, but when I look at the Vmp specifications it is usually around 18v regardless of whether the manufacturere calls it a high or low voltage panel?!?

I don't understand this, please explain.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: low voltage vs high voltage solar panels
    rollandelliott wrote: »
    I see certain companies designate their panels as either being high voltage or low voltage, but when I look at the Vmp specifications it is usually around 18v regardless of whether the manufacturere calls it a high or low voltage panel?!?

    I don't understand this, please explain.

    In this context it's about connecting in serial for a high Voltage array as would be used on a grid-tie inverter.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
    Re: low voltage vs high voltage solar panels

    Would need links to know--But as Marc says, the "low voltage" panels are typically older and for charging off-grid battery banks... The few rated I have seen are around 75 VDC maximum string voltage.

    The once used for grid tied are rated around 600 to 1,000 volts (for north America, all AC "household" wiring and devices are rated to 600 VAC).

    Otherwise, the panels over 100 watts are, for the most part, designed for use with AC Grid Tied systems and really do not have a standard Vmp voltage (like ~17.5 volts for charging a 12 volt battery bank on a PWM controller).

    I have seen here panels with Vmp somewhere around 100+ volts (a large amorphous panel--if I recall correctly).

    With Grid tied, there is no reason to have a "standard" Vmp voltage...

    However, with MPPT type charge controllers rated 150 VDC maximum--there is a zone where panels rated ~50 to 70 volts cannot be used to charge a 48 volt battery bank... The Vmp voltage is too low to recharge a 48 volt bank on a hot day--and yet, when you put too panels in series, the Voc voltage on a very cold day can get over 150 VDC.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    #4
    Re: low voltage vs high voltage solar panels

    first one is high voltage and second one is low voltage. can one use the "low voltage ones anyways for a grid tie inverter? In this example the high voltage one actually is higher voltage 24v vs 17v.

    SUN Solar Panel 190 Watts 26.70 Vmp $294.50
    Pallet Price/Watts: $ 1.39
    Model SV-T-190 HV
    Power (W) 190 Watts
    Open Circuit Voltage (V) 32.80 Voc
    Short Circuit Current (A) 8.05 Isc
    Maximum Power Voltage (V) 26.70 Vmp
    Maximum Power Current (A) 7.12 Imp
    Voltage Type High Voltage
    Length 61.85" ( 1,570.99 ) mm
    Width 37.44" ( 950.98 ) mm
    Depth 1.61" ( 40.89 ) mm
    Weight 41.00 lb ( 18.60 ) Kg
    Certifications None
    Grade B Warranty 30 Years

    SV Solar Panel 190 Watts 17.40 Vmp$294.50
    Pallet Price/Watts: $ 1.39
    Model SV-T-190 LV
    Power (W) 190 Watts
    Open Circuit Voltage (V) 21.50 Voc
    Short Circuit Current (A) 11.95 Isc
    Maximum Power Voltage (V) 17.40 Vmp
    Maximum Power Current (A) 10.92 Imp
    Voltage Type Low Voltage
    Cell Type Poly-Crystalline
    Length 61.85" ( 1,570.99 ) mm
    Width 37.44" ( 950.98 ) mm
    Depth 1.61" ( 41.00 ) mm
    Weight 41.00 lb ( 18.60 ) Kg
    Certifications CE, TUV, CETLUS, UL, PVCYCLE
    Grade B Warranty 30 Years
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: low voltage vs high voltage solar panels

    Usually the manufacturer will include in the specs something like: "Maximum system Voltage 600". Merely saying "low Voltage" or "high Voltage" is vague, as the terms are subjective.
    The reason being that central grid-tie inverters have arrays that will have a Vmp of 300-400 Volts. If one of the panels isn't rated for this kind of Voltage, it will fry.
    I'd suspect the "low Voltage" edition is designed for off-grid, battery charging applications where the Vmp or nominal Voltage wouldn't exceed 60 or 100.
    Perhaps you can contact the manufacturer for clarification.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #6
    Re: low voltage vs high voltage solar panels
    rollandelliott wrote: »
    first one is high voltage and second one is low voltage. can one use the "low voltage ones anyways for a grid tie inverter? In this example the high voltage one actually is higher voltage 24v vs 17v.

    SUN Solar Panel 190 Watts 26.70 Vmp $294.50
    Pallet Price/Watts: $ 1.39
    Maximum Power Voltage (V) 26.70 Vmp
    Certifications None

    SV Solar Panel 190 Watts 17.40 Vmp$294.50
    Pallet Price/Watts: $ 1.39
    Maximum Power Voltage (V) 17.40 Vmp
    Certifications CE, TUV, CETLUS, UL, PVCYCLE

    Interesting in that Grid Tied (usually using "high voltage") panels should always be TUV/UL/NRTL Certified--Battery systems it is a good idea, but not many people will enforce the code...

    So, the second "low voltage" panels have "more value" for most people because of the Certs.

    Voltage wise--The Vmp=17.4 volts is a bit more versitle because it can be used with both PWM or MPPT type solar charge controllers with standard 12/24/48 volt battery banks.

    The high voltage one is really only practical to use with PWM controller on 48 volt banks. (Of course, you can use with MPPT on any voltage bank using normal rules).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: low voltage vs high voltage solar panels

    in direct answer to your question if low voltage panels can be used in a gt system the answer is yes, if the pv is properly certified (ul is an example) and is rated for at least 600v.
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