Sunpower 435 watt solar charger help wanted

Theiceman
Theiceman Registered Users Posts: 1 ✭
in Solar Beginners Corner #1


I have 12 of these panels to hook up. What size or type of controller do I need?  I blew a 30 amp already.  
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Theiceman said:
    I have 12 of these panels to hook up. What size or type of controller do I need?  I blew a 30 amp already.  
    I guess I tell people this a dozen times a day, but quit buying stuff until you know your needs.

    To tell you anything we would need to know the voltage and size of your battery bank. 

    More important, would be if these will serve your needs, what loads are you trying to run, and where do you live (so we can check local available sun exposure average)
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Just me being a jerk, because I'm watching the most boring pool match ever. Here's a rough idea of correct answers.

    You have 12 - 435 watt solar panels, or an array of 5220 watts.

    If you have a 48 volt battery bank you would need roughly 5220 ÷ 48 volts = 109 x .75(for rough realistic output of array) 81.75 amps Output through a MPPT type controller, but the VMP is 72.9 so likely too high to use a Midnite classic 150, even with the OVER VOC safety feature unless you live in a pretty warm climate. This would require the array to be configured as 6 strings of 2. $650-700 if it fits.

    Alternately with a 48 volt battery bank. You could configure as 12 parallel panels and use a much cheaper PWM charge controller. Output then would be 5.97 amps x 12 or about 70 amps, You could split it up on 2 Xantrex C40's, or go to an off brand or European brand PWM controller.

    If you are charging a 24 volt battery bank double the numbers for MPPT type controllers with both limiting (I think too lazy to do the math tonight), with a 12 volt system 6x the MPPT controllers You could use cheaper MX80 controllers.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    The other thing to look at... Your have 12 panels which breaks down into 1 series x 12 parallel, 2 series * 6 parallel, 3 series x 4 parallel, 4 series x 3 parallel, and 12 series.

    1 * 72.9 Vmp = 72.9 Vmp-array
    2 * 72.9 Vmp = 145.8 Vmp-array
    4 * 72.9 Vmp = 291.6 Vmp-array
    6 * 72.9 Vmp = 437.4 Vmp-array
    12 * 72.9 Vmp = 874 Vmp-array

    And those are "nominal" working voltages for the possible arrays... The worst case voltages are roughly 80% of the above for the "low" working voltage. And something like 1.6x the above voltages for maximum array voltage.

    Hot panels (full sun, hot weather), the Vmp falls. Subfreezing weather, the Vmp (and Voc) voltages increase.

    And as Photowhit asks... Also depends on Battery Bank voltage too.

    A 48 volt battery bank, you can use a PWM controller + 1s x (up to) 12p panels to power the bank. PWM controllers are the cheapest types out there.

    If the battery bank is less than 48 volts (12/24 volts), you need an MPPT (maximum power point tracking) to efficiently down converter higher voltage / lower current array to the lower voltage/higher current battery bank.

    Also--If you put panels in series--Then you need an MPPT controller to down convert to any battery bank voltage.

    Note that this panels are relatively high Vmp/Voc per panel ratings. Unless you are on a tropical Caribbean island or similar, even 2 in series is too high of working voltage for the "typical" 150 Volt Max input MPPT controllers...

    You would need 200 or 600 volt input controllers--Which are not cheap.

    And also, need the battery bank voltage... Power = Voltage * Current... A 24 volt bank needs 2x larger MPPT controller (current rating) than a 48 volt bank to manage the same array wattage (1/2 the voltage * 2 types the current = Same Wattage).

    These days, the solar panels are almost the "cheapest" parts of the system. The Charge Controllers, Battery banks, Wiring, Racking for Solar Panels, etc... add up to the most expensive parts of the system.

    And while solar panels can easily last 20-25+ years, batteries may last 3-7 years (FLA in warm climates), and electronics can last 10+ years before replacements are needed (older than 5+ years, can be difficult to impossible to repair existing hardware).

    Details matter here... Do you have a plan on what you want to do with the solar panels? Grid Tied solar--Actually can save your money on your energy bill with the least amount of hardware and costs (just a Grid Tied inverter + Racking + some AC wiring).

    If you want to go off grid / have battery backup AC power -- That is not cheap and you really need to pencil out some system designs and see how they work for your and what they cost.

    Do you want one large system for your home? Or a couple smaller/portable systems for camping/cabin/RV use...

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