pablopet avatar image
pablopet asked

MPPT Sizing by ChatGPT - Google Gemini

Hi Guys,

I'm learning about solar and while trying to figure out how to size the MMPT that I will need to support the 2 strings (13 x 545 W panels each string) I would like to install, I was wondering if Chat GPT or the New Google Gemini AI were able to calculate it properly, it is just an experiment and both AIs seems to be able to calculate everything and offer a recommendation.

Unfortunately I'm not able to judge if they really know what they are talking about or just "pretending to know" and offering an advice based on their ignorance! :D

If anyone experienced is interest (Just for Fun) in taking a look at the answer (attached as image) would be cool to check if they answered correctly or if the are just Artificial Rubbish! :D

The prompt I entered was:

"What victron MPPT is needed to support 2 solar panels strings put in parallel, where each string is comprised of 13 solar panels connected in series and each solar panel STC Characteristics are: a 545 Maximum Power, a 47.0 Open Circuit Voltage, a 14.86 Short Circuit Current, a 39.0 Maximum Power Voltage, a 13.97 Maximum Power Current and a 20.9 Module Efficiency?"

That info correspond to the TW Solar TH545 Panels

And the AI answer is on the attached image.


MMPT Sizing by ChatGPT.jpg

I will presume the answer is wrong but I cant really tell.
Note: I know there is a solid MPPT Calculator and tone of info to properly design the system and I'm planning to use it of course, I'm not that lazy to expect that an AI will do all the analysis for me, but I just thought how cool it could be if you can provide info about your today's house energy consumption, your expectations (on-grid/off-grid, expected savings, locations, a blueprint of your house, etc.) and get in return a properly sized PV System with the required Bill of Materials, diagrams, etc no?
I have no doubt we will see something like this rather sooner that latter, even Victron itself could be already thinking in something similar.... or not! :)



solar sizingmmpt
1 comment
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klim8skeptic avatar image klim8skeptic ♦ commented ·

@PabloPet I will presume the answer is wrong but I cant really tell. Your question is also wrong. You forgot to include the battery voltages and lowest array temperature expected. GIGO...

Please use the Victron mppt calculator.

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3 Answers
pablopet avatar image
pablopet answered ·

Thanks Klim8skeptic, the battery voltage is 48V and the lowest temp of the array is -10C.

I have used the the Victron MPPT Calculator, using the Panel specifications described above, however I cant understand why the calculator is limiting me to put only 4 panels in series and only 3 arrays in parallel, I'm sure I'm doing something wrong but I cant figure out what, for expample:

if the 250/100 MPPT can accept up to 250 V and 100Amp, why only 4 panels in serie when each panel is 39v?

1) Victron Calculator
---- Max # Panels in Serie = 4 (4 x 39 = 156V at 13.97Amps)
---- Max # of Arrays in Parallel = 3 (3 x 13.97 = 41.9Amps)

2) My Calculations

---- Max # Panels in Serie = 6 (6 x 39 = 234V at 13.97Amps- well above the 250V limit)
---- Max # of Arrays in Parallel = 7 (7 x 13.97 = 97.79Amps - within the MPPT limit)

3) Artificial Intelligence Calculations
---- Victron 250/100 will support 24 panels easily! :D

Again, looking for advice from people who knows from real life experience how to properly calculate how many panels you can put in serie to reach the maximum allowed volts and how many arrays to reach the maximum allowed amps.



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pwfarnell avatar image pwfarnell commented ·
@PabloPet have you read any manuals or datasheets on the Victron MPPTs. The 250/100 has an input voltage limit of 250V and an output current limit of 100A in the calculator it says output. Nominal 54V battery means that the 100A limits the MPPT to 5400W, so 10 panels at most for maximum harvest, 12 panels allowing for some over panelling.

The 250V limit is a hard limit, exceed this and you can damage the controller so you keep a healthy margin. 47.0V is the Voc at 25degC, which will increase to around 52V when cold so you can only get 4 panels in series, the calculator lists the max cold voltage, all the info is there, but you need to understand solar panels more so read around.

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pablopet avatar image pablopet pwfarnell commented ·
Thanks @pwfarnell !

Sorrry didnt noticed the output part :(
Yes, I will keep reading everything I can, eventually I will feel confident enough but even then, nothing replace real life experience because manytimes reality differs from papers and websites so I hope the community will help! ;)

Once again, thanks for helping me notice!


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klim8skeptic avatar image klim8skeptic ♦ pablopet commented ·
@PabloPet Got a panel spec sheet? Looks like a 72 cell panel, but searching brings up a dozen different TW solar 545 panels.,
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pwfarnell avatar image
pwfarnell answered ·

Apart from a bunch of misinformation on the Victron MPPT 250/100, which is not suitable for your panels, it screws up the answer on the current from one string, point 3, a string of panels in series has the same Isc and Imp as a single panel, this is so basic that anyone with a small amount of electrical knowledge should spot it.

This begs the question, if you can not readily tell that the answer is completely wrong then should you be designing a 14kW power generation system with voltages in excess of 500V DC.

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kevgermany avatar image
kevgermany answered ·


If it helps, the input current limit of the MPPT is the short circuit current/Isc of the MPPT. The panels must be configured so that the panels cannot exceed this.

The shortcoming of AI is that it answers based on information that it's been trained on. Let's assume it was trained correctly at one point. Unless you turn off its learning ability, it will update this training with anything new it finds on the web. Including misinformation and errors.

In this case it looks as if there's been no specific training from the start. Despite that it has done a reasonable job, but reasonable is not good enough. It will lead to equipment damage, potentially fire and loss of life. The input voltages of a 250V panel setup are high enough to kill.

It's great that you are raising awareness of the chatgpt shortcomings. It's very worrying that for everyone like you that is suspicious of the results, there will be others who just accept them, with potentially catastrophic results.

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