Can east and west solar bank both run to same PWM controller?

softdown
softdown Solar Expert Posts: 3,896 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Hoping to install about 600 watts of panels facing east and about 600 watts facing west. Both running to one PWM controller and battery bank. Wanting to make sure this is a decent idea.

As an aside, sometimes I wonder if, for example:
four panels to east
eight panels to south
four panels to west
Would, real world, outperform:
sixteen panels to the south

I know it is best to consume power when it is being produced. This configuration would surely more than double the hours of power being produced. While lowering "spikes" to the battery bank.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
    Yes, it will work fine. Do a search on "virtual tracking" or "virtual tracker". If you are grid tied and have an infinite battery, it is not as optimal as having a single south facing array.

    There are some caveats... make sure all strings are the same voltage, and make sure that within each string all panels have the same orientation.

    By the way, when there is no direct sun (cloudshine conditions), the split array works just as well as a single south facing array.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #3
    As I seem to recall:
    Virtual tracking requires an MPPT controller.
    Feasibility is sometimes hotly debated.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    softdown wrote: »
    As I seem to recall:
    Virtual tracking requires an MPPT controller.
    Feasibility is sometimes hotly debated.

    I don't see why would it require an MPPT controller, can you explain?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #5
    Are you saying that all panels can be put on the same charge controller? My memories are a bit rusty though I know that opinions are divided on the feasibility of virtual tracking.

    I'd research it but focused on some major construction projects that need to be finished pretty soon.
    vtmaps wrote: »

    I don't see why would it require an MPPT controller, can you explain?

    --vtMaps

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    softdown wrote: »
    Are you saying that all panels can be put on the same charge controller?
    Yes, with some caveats. All panels in any one string must have the same orientation. The Vmp of each string must be the same.
    softdown wrote: »
    My memories are a bit rusty though I know that opinions are divided on the feasibility of virtual tracking.
    I don't recall any discussions of its feasibility. Whether virtual tracking is desirable or cost effective in any particular situation is another issue altogether.

    In a grid tied system with good net metering, virtual tracking may not be optimal. Some time-of-use plans may make it more desirable (if you pay more per kwh in the afternoon, a west facing array may be very cost effective). In some roof mount systems (depending on roof angles and surface area) virtual tracking may allow greater solar harvest per day, even if the harvest per sq ft of panel is not as optimal as a 100% south facing array.

    In an off grid system, virtual tracking may allow a longer charging day... less overnight time on battery power. When sunshine is not direct (cloudshine), a south facing array has no advantage over an east, west, or even north facing array.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Specifically, MPPT controllers attempt to find the Vmp-array (optimum operating voltage for the solar array). Since Vmp for a panel is temperature dependent (and, of course, construction of the panel dependent too)--If you have "missmatched" panels on a single array for the MPPT controller--There is no "one" optimum operating voltage Vmp-array, and it is possible that the of the two or more Vmp-array "local peaks", that the MPPT controller may "lock on" to the smaller peak.

    For PWM controllers--Since you pick the array voltage to be ~18 volt for a 12 volt battery bank--You can have several panels pointing several directions on one PWM controller without problem. The PWM controller does not adjust to match Vmp-array--It just takes all of the available current and pipes to to the battery bank (as needed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #8
    BB. wrote: »
    Specifically, MPPT controllers attempt to find the Vmp-array (optimum operating voltage for the solar array). Since Vmp for a panel is temperature dependent (and, of course, construction of the panel dependent too)--If you have "missmatched" panels on a single array for the MPPT controller--There is no "one" optimum operating voltage Vmp-array, and it is possible that the of the two or more Vmp-array "local peaks", that the MPPT controller may "lock on" to the smaller peak.

    For PWM controllers--Since you pick the array voltage to be ~18 volt for a 12 volt battery bank--You can have several panels pointing several directions on one PWM controller without problem. The PWM controller does not adjust to match Vmp-array--It just takes all of the available current and pipes to to the battery bank (as needed).

    -Bill


    In a simple system with parallel panels I agree. In large systems with possible series- parallel arrays pointing different directions this would be suspect and so one would be using multiple MPPT controllers to harvest the max reliably.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #9
    Yesterday I called my panel manufacturer, Grape Solar, about getting more panels like the ones that I have. Home Depot quit listing this size on their web site.

    This what the tech told me:
    Manufacturers have switched from 5" cells to 6" cells. Sharp may still have have some 5" cells around 190 watts but they want $600/panel (which is crazy).

    The east and west panels should be on a different controller but can use the same battery bank. I had thought the different controllers would "battle" each other.

    My panels make enough power. My problem with them is they only make optimal power for a few hours/day. It would be easier on the batteries if they made power from sun up to sun down. This is common sense.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #10
    On your flooded battery the different controllers probably are fine. With an AGM or a battery that can't tolerate very slight voltage spikes above the set-point one would network the controllers. This can really help during absorption when loads are switching. Yes it is common sense to track the sun offgrid.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    And finding out that your "cheap" solar panels you bought yesterday are not available today (to infill the array, replaced a broken panel, etc.) is common--And frustrating.

    More or less, the production life from many "popular" electronics (and solar) devices is in the range of 18 to 24 months. After that time frame, no-more.

    There are some devices (like solar charge controllers and AC inverters that have much longer production life cycles)--But these tend to be specialized companies (like Midnite, Outback, MorningStar, etc.) that are designing for a specific market (with higher priced equipment).

    And believe me, the engineers/product reps. are constantly pulling their hair out too over short life cycles for major components which are in their "long life cycle products" (micro processors, memory, etc.) that also have ~2 year product life cycles.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #12
    Ahem....they cost ~$2.00/watt a few years ago. My solar is anything but cheap....though I don't think you meant a slight.

    What will happen when the inverter patents expire and the Chinese start competing with Outback, Midnite, and MorningStar? Personally...I see a lot of Zantrex.
    BB. wrote: »
    And finding out that your "cheap" solar panels you bought yesterday are not available today (to infill the array, replaced a broken panel, etc.) is common--And frustrating.

    More or less, the production life from many "popular" electronics (and solar) devices is in the range of 18 to 24 months. After that time frame, no-more.

    There are some devices (like solar charge controllers and AC inverters that have much longer production life cycles)--But these tend to be specialized companies (like Midnite, Outback, MorningStar, etc.) that are designing for a specific market (with higher priced equipment).

    And believe me, the engineers/product reps. are constantly pulling their hair out too over short life cycles for major components which are in their "long life cycle products" (micro processors, memory, etc.) that also have ~2 year product life cycles.

    -Bill

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    #13
    softdown wrote: »
    Ahem....they cost ~$2.00/watt a few years ago. My solar is anything but cheap....though I don't think you meant a slight.

    What will happen when the inverter patents expire and the Chinese start competing with Outback, Midnite, and MorningStar? Personally...I see a lot of Zantrex.





    The Chinese disregard ISO, UL, ETL, TUV requirements.

    (IF) the Chinese ever decide to pay for the listings the price is in effect more expensive than what people pay for american, or made in mexico inverters because of the 30% tarriff that is put in place. Once the Chinese pay for the appropriate standards, patents, and safety listings it actually makes their products more expensive, one of the main reasons they avoid going through the proper channels to meeting code requirements both nationally and internationally.

    (I.E) apple makes the Iphone6 in china but to follow ISO, FCC and quality control standards the Iphone 6 costs over a $1000 instead of $500.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #14
    Cheap as in $1 a Watt yesterday, and $3 a Watt or more (if you can find any) to add on or replace damaged panels.

    Did not intend to imply poor quality. .. Just supply and demand.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #15
    Believe that sd liked the Grape Solar 190s for a number of reasons, including that they could arrive at a local HD store without extra freight, IIRC ...

    FWIW, the Host of this site has Topoint 190 W PVs, which have a Vmp of 36.5 V -- very close to that of the Grape 190 specs that I have been able to find:

    http://www.solar-electric.com/topoint-jtm-190-72m-solar-module.html

    There will be some freight involved, or a trip to AZ. Wind-Sun often has very good freight charges, IMO.

    I have no direct personal experience with Topoint, but, Wind-Sun has carried them for about 18 - 24 months.

    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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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #16
    Those are the exact same panels as what I have. So they would work well. Can't seem to recall if east and west facing panels should be mounted at same inclination as south. I did the south at 45 degrees and I'm happy with that.

    PV watts has changed from when I was able to use so well it last winter.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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