KJINTF
Western Montana
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Salvo
It was simply a KISS example nothing more
Sorry it got your hackles up
Without specific numbers on your graphs there is no way to determine reality
The example was only an example to set the stage for MY QUESTION
Nothing more
Can you tell me
How do the different manufacturers software algorithyms effect the gain of the MPPT controllers?
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Salvo
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KISS is a good approach as long as it doesn't introduce gross errors.
Using KISS, you probably introduced a 50% gain error!
KJINTF wrote:
It was simply a KISS example nothing more
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KJINTF
Western Montana
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50% up or 50% down depends on conditions
Got any real numbers for those graphs
Still looking for a response on how I can measure the "GAIN" from the software?
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liborko
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Lets look at the numbers my calculator is giving me. Lets take the most favorable numbers for the PWM controller which is Isc=8.37A. As this is a short circuit current, the estimates will be too optimistic. At different battery voltages the actual current will be less. Lets take the above Kyocera 135W panel as an example for comparison. The calculations assume the solar panel is pushing current into the batteries at different voltages:
Vmp=P:Imp=135W:7.63A=17.69V
PWM controller:______________MPPT controller:____________gain:
8.37A*12V=100.44W____________135W:12V=11.25A_____________34.4%
8.37A*12.5V=104.62W__________135W:12.5V=10.8A____________29%
8.37A*13.0V=108.81W__________135W:13.0V=10.38A___________24%
8.37A*13.5V=112.99W__________135W:13.5V=10.0A____________19.5%
8.37A*14.0V=117.18W__________135W:14.0V=9.64A____________15.2%
8.37A*14.5V=121.37W__________135W:14.5V=9.31A____________11.23%
In the above calculation, the Isc=8.37A is much lower in reality because the actual current is voltage dependent and without actual I/V curve is impossible to determine. And it is assumed that the PWM controller is @ 100% duty cycle, another overestimate. On the other hand, it is assumed that the MPPT controller is operating at 100% efficiency. From the above calculation it is also obvious that PWM controller never extracts full power the solar panel is capable of.
And the solar panel in question is optimized for PWM controller.
If the solar panel was optimized for MPPT controller, the MPPT controller would leave PWM controller in dust.
How do you measure a gain? My Blue Sky 3024i controller with IPN PRO monitor panel/programmer reads both input and output controller currents and the gain I see on regular basis is in the 15-20% range. To do simple measurement, install DPDT switch to bypass the controller to see the difference between the panel current and the output current from the controller.
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christopherglenn
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The big advantage of the mppt is when the batteries are very low. Then you are pushing ~11.x volts into the batteries off a 17 volt panel. Once the batteries are charged, there is not much to be gained on a 14.5 volt battery off a 17 volt panel (there are voltage losses in the switching transistors, ~.7 volts each, and in the wiring on both sides on the controler). If you have panels over ~20 volts, mppt wins no matter the charge state.
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KJINTF
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Hi guys
Thanks for the calculations and comments
I believe most, if not all, of us are well aware of the advantages offered by MPPT controllers over the traditional PWM controller. For folks looking for additional information and or other points of view I suggest reading several of the many MPPT owners’ manuals from Blue Sky, Rouge, Morningstar, Outback and MidNite Solar. They are all available on line and many include excellent educational material.
My intent for this thread was to take this to a higher level, comparing / contrasting the differences between the several good and few great MPPT controllers available today.
They all offer “tracking” the “T” in MPPT however they all do it differently some far superior than others.
This TRACKING function supplies the “GAIN” I am asking about
NOT the differences between MPPT and PWM
I plan on purchasing two or three of the better known MPPT (15 to 30amp) range controllers (trying to keep the expense down a bit plus I already have the TS MPPT 60) I will then make some real world measurements
Suggestions as to which make and model would be appreciated
It was never my intent to argue about the double digit % gains offered from a MPPT controller over the traditional PWM controller. I am simply looking to better understand the current state of the microprocessor controlled technology in the higher end MPPT controllers.
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smkettner
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I would like to hear more details on the "far superior" models and what sets them ahead of the other MPPTs.
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CA Traveler
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Looking forward to your results.
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N8GS
West Michigan
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KJINTF wrote:Hi guys
Thanks for the calculations and comments
I believe most, if not all, of us are well aware of the advantages offered by MPPT controllers over the traditional PWM controller. For folks looking for additional information and or other points of view I suggest reading several of the many MPPT owners’ manuals from Blue Sky, Rouge, Morningstar, Outback and MidNite Solar. They are all available on line and many include excellent educational material.
My intent for this thread was to take this to a higher level, comparing / contrasting the differences between the several good and few great MPPT controllers available today.
They all offer “tracking” the “T” in MPPT however they all do it differently some far superior than others.
This TRACKING function supplies the “GAIN” I am asking about
NOT the differences between MPPT and PWM
I plan on purchasing two or three of the better known MPPT (15 to 30amp) range controllers (trying to keep the expense down a bit plus I already have the TS MPPT 60) I will then make some real world measurements
Suggestions as to which make and model would be appreciated
It was never my intent to argue about the double digit % gains offered from a MPPT controller over the traditional PWM controller. I am simply looking to better understand the current state of the microprocessor controlled technology in the higher end MPPT controllers.
I might be able to help with your tests. I have the Outback FM-60 controller. I also have an 8 channel 16 bit data logger. I have already done some testing. When you get your test set up let me know what parameters you are tracking and I will set up my equipment to match your set up. PM me if interested.
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Salvo
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That definition won't work. MPPT gain is now a function of panel voltage. Gain becomes a nonsense quantity.
Let's take for example two 130W panels. In order to keep it simple, we will neglect cable and converter efficiency losses.
Panel 1: your traditional 36-cell 12V panel.
Vmp = 17.7V
Imp = 130W/17.7V = 7.34A
Panel 2: A 200-cell panel.
Vmp = 17.7V * 200/36 = 89.3V
Imp = 130W/89.3V = 1.455A
Calculating gain using your definition: G = 1 - (I_out / I_in):
Panel 1: Gain = 1 - (130W / 12.7V) / 7.34A = 39.4%
Panel 2: Gain = 1 - (130W / 12.7V) / 1.455A = 604%
Panel 2 has a "gain" of 604% while Panel 1 has a "gain" of 'only' 39%. In essence, this is the crux of the MPPT hype. In reality, both panels will output approximately equal current.
If you use that definition, you will become an official member of the MPPT fan club. That would be a disservice to those trusting you to provide honest information on the pros and cons of MPPT vs. PWM controllers.
Sal
KJINTF wrote:
They all offer “tracking” the “T” in MPPT however they all do it differently some far superior than others.
This TRACKING function supplies the “GAIN” I am asking about
NOT the differences between MPPT and PWM
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