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  • Split Arrays on two controllers

    Just wondering if anyone has experience with wiring two arrays to two different controllers in a different way. I have two Tristar MPPT 60A and two arrays A = 5KW 24x Hyundai 210W facing South West and B = 4KW 18x Scheuten 210W facing South East. Question is would I be better wiring one array to one controller and let the TS power shaving take care of the over sized arrays or as someone else suggested to split the arrays between the two controllers, 50% on each which I am told would work better for my South East/ West setup and put less strain on the controllers. I wonder if I split the arrays will there be shading issues early and late in the day where I will lose power.

    Battery is 48V 1000AH Eternity deep cycle & 6KW 48V Voltec Inverter
    Last edited by rithym; 06-17-2018, 06:45 AM.

  • #2
    Arrays have to be matched if they are going into the same controller. You can't parallel a 9 panel 300V array with a 12 panel 400V array.

    What sort of battery voltage are you looking at? 5Kw @ 48V is 83 A, over the 60A controller limit ?
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      All the panels from both arrays match outputs pretty closely even though from different manufactures so it's pretty much like having a 9KW array split between two 60A controllers. Yes, both arrays are well over spec but the Tristar MPPT controllers have power shaving built in so they will just go up to the max 60A each and ignore the rest with no harm apparently, this is an advantage on cloudy days more power in to the battery. I have the 4KW array facing South East as that is sunrise when the temp is cooler here in Portugal but the 5KW is South West for sunset when summer temps here go up to 40 C and there will be more losses due to the higher temps.
      I guess the main question I am asking is if I split the arrays 50% between controllers will there be an issue with loss of power when half the panels are in full sun and the other half are shaded (like would be the case early & late in the day).

      Put another way imagine having two identical solar panels, one facing South East and the other South West. If they are both on one MPPT controller in parallel would there be an issue when one panel is in full sun and the other in shade ie the shaded panel pulls power from the one in full sun?

      I guess this is an issue with how the software in the controller deals with the power point between a panel in full sun and another in full shade but Morningstar have been less than helpful and I just wondered if anyone on this forum had experience with splitting arrays on a single TS MPPT controller and how this is dealt with by the software...
      Last edited by rithym; 06-17-2018, 02:12 PM.

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      • #4
        I would think, if you only have one input into the controller and are paralleling two differently oriented arrays there would be an issue trying to get the maximum power point . On the other hand combining these two arrays in series would bring down the higher current array to the low current array.
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          Originally posted by littleharbor View Post
          I would think, if you only have one input into the controller and are paralleling two differently oriented arrays there would be an issue trying to get the maximum power point . On the other hand combining these two arrays in series would bring down the higher current array to the low current array.
          Can you please elaborate on your point with an example of alternate wiring. I always understood that 'series' means doubling the voltage unfortunately the TS controllers claim 150V max but de-rate significantly over 115V with the newer software. My strings are 3x8 (24 Hyundai panels) and 3x6 (18 Scheuten panels) which, split 50% between controllers would be 4 + 3 strings on each controller...

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          • #6
            So then you are asking about paralleling the different arrays. They will have completely different current except possibly when the sun is midway between the different arrays. I don't really understand the fine details of MPPT controllers but seems to me the differing output of your panels would cause difficulty for the controller in finding the maximum power point MPPT, to track. Somebody here may correct me or be able to explain better what I'm saying.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #7
              Originally posted by littleharbor View Post
              So then you are asking about paralleling the different arrays. They will have completely different current except possibly when the sun is midway between the different arrays. I don't really understand the fine details of MPPT controllers but seems to me the differing output of your panels would cause difficulty for the controller in finding the maximum power point MPPT, to track. Somebody here may correct me or be able to explain better what I'm saying.
              Okay so you have grasped my specific question regarding splitting arrays on an MPPT controller. As you suggest perhaps someone with experience of trying this can shed some light on the question I have tried Morningstar Technical but they seem to have no idea on paralleling East & West arrays and how the software deals with tracking the MPP... their suggestion was to buy more controllers!

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              • #8
                They (Morningstar) may be right. lol
                I'm sure someone will chime in here with a detailed explanation as to whether or not you can do this and why.
                2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                • #9
                  The MS-MPPT-60 (I have 2 of them) is pretty rugged. I have a 3Kw array on one (my largest array, faces south) and on a hot summer day, in the battery shed, gets the controller going really hot. Yes, it's got thermal and current foldback to keep parts in the safe zone.
                  on to parallel arrays
                  The voltage needs to match pretty closely. whichever array has the lowest VMP, is going to drag the other array down to the same voltage. 2 or 3 volts won't be an issue. 20V, you are looking at some larger losses, and maybe problems with the higher voltage overdriving a lower voltage array. You will need combiner box, breakers for each string and then you send the combined output to the CC.
                  Using arrays as a virtual tracker is common, but the arrays have to match in voltage. Since you have NOT told us any numbers, other then kw of arrays, it's all on you to not burn yourself up.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by Mike90250 View Post
                    Using arrays as a virtual tracker is common, but the arrays have to match in voltage. Since you have NOT told us any numbers, other then kw of arrays, it's all on you to not burn yourself up.

                    Information taken directly from MS String Calculator online

                    Hyundai Array South West 8 strings of 3 panels 5KW
                    Minimum Voc (average high temp.) 86.83
                    Max. Operating Voc (record low temp.) 98.79
                    Max. Voc (record low Temp., morning) 107.33 < 150 Max. Vin
                    Minimum Vmp (average high temp.) 67.03 > 60.00 Vb Max.
                    Maximum Vmp (record low temp.) 78.99
                    Isc (STC) 8.20
                    Imp (STC) 7.80

                    Scheuten Array South East 6 strings of 3 panels 4KW
                    Minimum Voc (average high temp.) 85.80
                    Max. Operating Voc (record low temp.) 97.61
                    Max. Voc (record low Temp., morning) 106.05 < 150 Max. Vin
                    Minimum Vmp (average high temp.) 66.80 > 60.00 Vb Max.
                    Maximum Vmp (record low temp.) 76.61
                    Isc (STC) 8.33
                    Imp (STC) 7.85
                    Last edited by rithym; 06-18-2018, 12:08 AM.

                    Comment


                    • #11
                      I have now wired in the two arrays - South East 18 panels on TS MPPT A and South West 24 panels on TS MPPT B. Until I get a better understanding of splitting each array and any shading issues associated will stick with this configuration. MS technical have suggested wiring both ways to see which harvests the better energy but the last thing I want to do is void the 5 year warranty on the controllers.

                      Would still like to hear from anyone with experience of splitting arrays across controllers...

                      Comment


                      • #12
                        OK I am going to chime in. There is only one manufacture you can do this with and straight up is Morningstar MPPT. The issue is time it takes for controllers to react to fast changing conditions like a cloud passing by during mid day when batteries are on Bulk charge. If the controller cannot act fast enough with an over sized array will cause the output to exceed the controllers capabilities. Example 1000 watts on a 60 amp controller on 12 volt battery. A cloud passing by them clear can surge up to 80 amps and damage the MOSFET because the controller cannot limit current fast enough. But there are some caveats and conditions that must be met.

                        1. Panels minimum Vmp stays above battery Vb for consistent charging.
                        2. Array compensated Voc stays below Controllers Maximum Voc on coldest mornings.
                        3. Battery maximum charge rate is not exceeded. If you over power and use say a 60 amp controller, your battery better be able to handle 60 amps.
                        4. Diminishing Returns. Once you go above 20%, you are throwing away a lot of unused power that would otherwise be available.

                        As for Warranty as long as you use Morningstar, there is no problem over powering. What I can tell you without question, you will harvest more energy with two controllers.
                        Last edited by Sunking; 06-18-2018, 06:54 PM.
                        MSEE, PE

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                        • #13
                          Originally posted by Sunking View Post
                          As for Warranty as long as you use Morningstar, there is no problem over powering. What I can tell you without question, you will harvest more energy with two controllers.
                          These 210W panels I bought are old panels maybe 6-7 years so I tried to allow for age related losses but also where I live temps never go below 5 deg C but do get well over 35 in the summer so I also had to pay attention to min Vmp so it does not drop below my charging absorption voltage later in the day. None of these panels will work well on PWM controllers for exactly that reason and I guess that's why they were cheap... I bought Morningstar controllers as their online string calculator helped me match the controller to these cheap panels which came along first. Whilst researching controllers I came across a white paper on the MS website stating that over-sizing the array is not a problem with MPPT so it seemed logical to do this so on cloudy days I get a little more power to run the loads and perhaps charge the battery a little... time will tell if this logic works. Yesterday was the first full day of production since wiring the second array and both controllers are showing as 'Current Limiting' on their Data Log pages so must have hit the 60A ceiling at some point even though it was cloudy all day.

                          As the controllers are side by side I may re-wire the arrays to be split 50/50 on each controller later on once I have some data from the current configuration to compare. This is what MS technical advised me to do... As both arrays are well over-sized for 60A controllers it does make sense in my mind to split the arrays between controllers as (theoretically) more power will be harvested early and later in the day as the current limit will be 120A, not 60A. Whether this is actually the case was what prompted my original question as I just don't know how the controller will deal with half the array being in full sun and the other half in full shade...

                          Comment


                          • #14
                            I just don't know how the controller will deal with half the array being in full sun and the other half in full shade
                            Not a problem as long as the Vmp is very close with each array (which was already shown)


                            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                            solar: http://tinyurl.com/LMR-Solar
                            gen: http://tinyurl.com/LMR-Lister

                            Comment

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