Solar solution efficiently vs charge controller thoughts

fca1
fca1 Solar Expert Posts: 124 ✭✭
in Off Grid Solar & Battery Systems #1
Hi there my system was upgrade in July with another 3K watts and a midinite 150 charge controller..
One thing that i have observed along these months is that the midnite is always with less efficiency than morningstar .
I have easy calculation that is the output watts/rawWatts and is always under performing..
I know that there a lot of factors, but most of them are the same (panels, orientation, cables sizes and distances, strings voltage etc).
The big difference is the panels it self as the ones connected to the morningstar are cheap no brand chinese and the one connected to the midinite are "not so chinese" they luxor 250w mono panels (supposed to be better quality)..

some times i change the mode on the midnite from solar to dynamic and i get some more juice out of it...

I will do a test when changing (hopefully next month when my xantrex 48v inverter arrive) my system from 24v to 48v that is swap the arrays between charge controllers... At 24V the monrningstar can't cope with 3000W..

this was this morning and with was with the midnite in dynamic mode and early morning its even worst , also i open to some suggestions on the fine tuning of the midinite 150.

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thank you all for suggestions, advices on this ...
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #2
    Re: Solar solution efficiently vs charge controller thoughts

    This could be because of the multitude of factors. Either the panels are overrated or the controller doesn't track MPPT correct, which is again could be because of controller inability or incorrect settings.

    What are Vmp and Imp for these arrays?
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  • fca1
    fca1 Solar Expert Posts: 124 ✭✭
    #3
    Re: Solar solution efficiently vs charge controller thoughts
    NorthGuy wrote: »
    This could be because of the multitude of factors. Either the panels are overrated or the controller doesn't track MPPT correct, which is again could be because of controller inability or incorrect settings.

    What are Vmp and Imp for these arrays?


    Connected to morningstar 3 strings of 2 panels each


    panel 220w

    ippm 4.63A
    ISC 5.37A
    Vppm 47.5V
    Voc 53.7

    by string
    vppm =47.5*2 <=> 95v
    ippm = 5.37A

    by array
    vppm =47.5*2 <=> 95v
    ippm = 5.37A*3 <=> 16.11A


    Conected to midinite 4 strings of 3 panels each

    panel 250w
    impp 8.17A
    ISC 8.53A
    Vmpp 30.79V
    VOC 37.41V

    by string
    vppm=30.79*3 <=> 92.37V
    ippm =8.17

    by array
    vppm=30.79*3 <=> 92.37V
    ippm =8.17*4 <=> 32.68A
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Solar solution efficiently vs charge controller thoughts

    Efficiency of a charge controller is the real power (measured accurately under lab conditions) in versus the real power out. Not the relative Watts in compared to the panel rating.

    It will also vary on any controller with respect to how much it is loaded and the difference between array Voltage and system Voltage.

    You certainly can not compare efficiency between two controllers with two completely different arrays on each one. This is the sort of mistake made by diesel mechanics who think they know everything and insult the engineers who design this stuff. :p
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #5
    Re: Solar solution efficiently vs charge controller thoughts
    fca1 wrote: »
    I have easy calculation that is the output watts/rawWatts and is always under performing..
    I know that there a lot of factors, but most of them are the same (panels, orientation, cables sizes and distances, strings voltage etc).

    It is almost impossible to make this comparison when they are both powering the same load. Any inaccuracy in voltage setpoint means that one charge controller will not output its rated load.

    If you really want to test this get a good DC load (or even a discharged battery bank) and test them both separately, ideally with the same array in both cases. Use shunts to measure current; don't rely on commercial clamp-on meters.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Solar solution efficiently vs charge controller thoughts

    BTW the actual efficiency of any MPPT charge controller is >90%.
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  • fca1
    fca1 Solar Expert Posts: 124 ✭✭
    #7
    Re: Solar solution efficiently vs charge controller thoughts

    Im not after academic efficienty ....
    More like empiric view of my system ..
    As i told i will do the test of the same array on both Ctrls..
    Even that its misleading because another day another sun ;)
    But when I swap it I will see long the time if it changes
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Solar solution efficiently vs charge controller thoughts

    There is no point. The "efficiency" shown is not the efficiency of the charge controller. In fact it is not an efficiency rating at all. It is the percentage of STC rating of the panels' output at the moment. Has virtually nothing to do with the charge controllers and is quite irrelevant as array output will vary with sun, state of charge, and concurrent loads. It is a meaningless and misleading number.
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  • fca1
    fca1 Solar Expert Posts: 124 ✭✭
    #9
    Re: Solar solution efficiently vs charge controller thoughts
    Cariboocoot wrote: »
    There is no point. The "efficiency" shown is not the efficiency of the charge controller. In fact it is not an efficiency rating at all. It is the percentage of STC rating of the panels' output at the moment. Has virtually nothing to do with the charge controllers and is quite irrelevant as array output will vary with sun, state of charge, and concurrent loads. It is a meaningless and misleading number.
    Both cc are conected to the same batts / loads
    And its a number on the hipotetic Max of the Pvs vs what I'm getting..
    So I was considering my losses would be aboutv30% and is where I see that
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Solar solution efficiently vs charge controller thoughts

    Lower than array maximum potential is NOT a loss; it is the functioning of the array as per demand needs. When the batteries are fully charged and the loads are off the array output will be a very small percentage of STC rating. It means nothing in regards to the efficiency of the system; it's just how these things function.

    My array sometimes show >100% efficiency, so what does that mean? It means 3200' of elevation + edge-of-cloud-event makes for interesting, but meaningless, numbers.
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  • fca1
    fca1 Solar Expert Posts: 124 ✭✭
    #11
    Re: Solar solution efficiently vs charge controller thoughts
    Cariboocoot wrote: »
    Efficiency of a charge controller is the real power (measured accurately under lab conditions) in versus the real power out. Not the relative Watts in compared to the panel rating.

    It will also vary on any controller with respect to how much it is loaded and the difference between array Voltage and system Voltage.

    You certainly can not compare efficiency between two controllers with two completely different arrays on each one. This is the sort of mistake made by diesel mechanics who think they know everything and insult the engineers who design this stuff. :p
    Of course i know that im looking at this when in bulk when cc are pushing to batts the maximum. That they can..
    What I'm saying is not one single measure is trend that I see the Morningstar always getting more than the midnite not saying that is cc it could be the panels the cables etc
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: Solar solution efficiently vs charge controller thoughts
    fca1 wrote: »
    Of course i know that im looking at this when in bulk when cc are pushing to batts the maximum. That they can..
    What I'm saying is not one single measure is trend that I see the Morningstar always getting more than the midnite not saying that is cc it could be the panels the cables etc

    First thing you should check is the Voltage at the output of each charge controller with an accurate DMM. You'd be amazed what happens there. What is more, the two controllers don't deal with temp compensation the same. As such the chances of them ever agreeing on a Voltage point is slim, and so they will not divide up their share of work equally.

    In fact the only time you can get two controllers to completely agree is if you use two MidNites and the "follow me" function which slaves one to the other. Two different controllers will always behave differently. It is not really a flaw or problem, merely a characteristic.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #13
    Re: Solar solution efficiently vs charge controller thoughts
    fca1 wrote: »
    Connected to morningstar 3 strings of 2 panels each

    by array
    vppm =47.5*2 <=> 95v
    ippm = 5.37A*3 <=> 16.11A


    Conected to midinite 4 strings of 3 panels each

    by array
    vppm=30.79*3 <=> 92.37V
    ippm =8.17*4 <=> 32.68A

    One of the panels on the second array might be shaded/disfunctional. I would check for this. Start by measuring current on each of the strings to see if it all the same. If you find a string with lower current, it may contain a bad panel.

    If panels are Ok, then it looks like MidNight controller doesn't move the voltage high enough to hit the MPPT point. may be a glitch in the controller, or perhaps your settings are not correct (e.g. you specified your own MPPT profile or something of that sort).
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Solar solution efficiently vs charge controller thoughts

    MPP is whatever the controller judges it to be. This is not necessarily Imp * Vmp of the array.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #15
    Re: Solar solution efficiently vs charge controller thoughts
    Cariboocoot wrote: »
    MPP is whatever the controller judges it to be. This is not necessarily Imp * Vmp of the array.

    MPP is the voltage point, which would produce the maximum power (V*I). It exists independently of the controller. Controller may find it and produce the maximum, or it may wonder away from it and produce less.

    If, for the same conditions, one controller uses higher V and produces higher V*I, while the other uses lower V and produces lower V*I, then there's a problem with the second controller that prevents it from finding the MPP point.

    However, I'm afraid, in the OP case the conditions are not the same, and there could be a problem with some of the panels in the second array.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: Solar solution efficiently vs charge controller thoughts

    Does anyone know where I can get a shredder that does sheepskin?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #17
    Re: Solar solution efficiently vs charge controller thoughts
    Cariboocoot wrote: »
    Does anyone know where I can get a shredder that does sheepskin?

    try the big bad wolf.:p
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