PV generation seems limited

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florbid asked Mar 16, '24

PV generation seems limited

Hi,

I recently updated my system. Initially I had a 9Kw system with two strings, which on peak would generate around 8-9kw. (note, I have a 3 phase system)

The system has been upgraded and now has 4 strings and should be a 15Kw system.

The problem is the system now doesn't generate more than 10,2Kw and the strings seem to max at 3kw.

Also the Volts of the new strings are very high (350V and 400V on average, the old ones were 100V and 150V on average) and the Amps, which on the old strings were 30Amp each, have now dropped to 6Amp on average on the new strings and the old strings have dropped to 10Amp and 18Amp.

Overall, it feels like a big upgrade for no benefit.

Pic of the old system config and new one (the old strings are now string 3 and 4)

amps

screenshot-20211210-140847-samsung-internet.jpg (285.4 KiB)

victron-image.png (135.4 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2024-03-16T18:39:34Z

outsourcedguru answered · Mar 16 at 06:39 PM

In my case, my charging controller's model is Victron SmartSolar MPPT 150/100. The most important number in that is the "150" which means "maximum 150VDC in". Also in my case, I have four 400W panels that each have 45VDC/11A output maximum. In series they would present (4 x 45VDC = 180VDC) to the charge controller and it would have to shunt or otherwise ignore the 30V over-voltage. [Nick indicates that the 30VDC over-voltage would toast the MPPT = bad.] In parallel, they would present (4 x 11A = 44A) to the charge controller and that would be acceptable since it's below the "100" in the product's model number. [Nick says that the upper current limit on mine is actually 70A.]

Optimally, though, you want to maximize the presented voltage to the charge controller so I ran pairs of panels in series (2 x 45DC = 90VDC, 1 x 11A = 11A) and then connected the pairs in parallel (1 x 90VDC = 90VDC, 2 x 11A = 22A). The system is optimal at this point. I converted a friend's solar system to change his from eight panels in parallel to two sets of four in series; it's now twice as functional as before.

Is it possible that your voltage-in-series is now too high for your charge controller?

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nickdb ♦♦ commented · Mar 16 at 06:59 PM

You cannot exceed the 150V, it is a hard limit and will cook the mppt. Isc limit is 70A on the PV side. The 100A is max charge current on the DC charge output side at the battery voltage.

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Answer 2 · 2024-03-16T19:04:55Z

nickdb answered · Mar 16 at 07:04 PM

Which charger is this? RS450? That is the only model capable of those voltages and available in 100 and 200A variants.

High voltage equals lower current. Ohms law.

I suggest you use the MPPT calculator, enter your panel specs and confirm that you are correctly configured and designed.

Edit: I see its the 200A. So max power is 200A x battery voltage so around 10kW.

Various specs all in the datasheet. You have way overpanelled, typically no more than 30% (since typical loss from ideal conditions to the real world is roughly 1/3)

The calculator really should have been used before spending the cash.

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Answer 3 · 2024-03-16T19:18:58Z

delf67 answered · Mar 16 at 07:18 PM

OP has 4x 200A MPPTS.

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nickdb ♦♦ commented · Mar 16 at 07:28 PM

No. Those are the 4 trackers on a 200A RS450.

Kind of obvious from the common serial number.

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delf67 nickdb ♦♦ commented · Mar 16 at 07:37 PM

Sorry. My bad.

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