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Axpert VM III 5KW not charging or utilizing PV


Beejsteri0us
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Hi all! I’m new to this forum and also somewhat of a noob in solar installations but have a handle on most things.

I just setup an Axpert VM III 5 KW inverted with 3x 390W 24v solar panels in serial pattern.

everything works as it should from AC and Battery (Pylontech US2000B) but the PVs don’t charge the battery or supply power at all. The Solar icon flashes on the screen and they receive around 135v (zero watts and zero amp). The DC/DC icon never appears.

I am wondering if the PV panels are connected properly or if I need more than 3 panels? I was planning on getting another 3 panels hooked up in serial then paralleled together with the other 3. Would this solve the problem or am I doing something wrong?

Currently I am in SUB mode (bypassing the battery) to preserve cycles until this is figured out.

Any help would be greatly appreciated!B3BFF6D9-FA01-4668-AD46-13555038E3D4.thumb.jpeg.de3ee3eedfe723a873ef82ed8138fc44.jpeg

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Edited by Beejsteri0us
Added picture of controller and settings
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On 2021/01/25 at 7:09 PM, Beejsteri0us said:

Axpert VM III 5 KW inverted with 3x 390W 24v solar panels in serial pattern.

The Solar icon flashes on the screen and they receive around 135v (zero watts and zero amp).

135 V should in theory be enough to start using solar power, but my rule of thumb has been that you need 6 panels minimum for these high voltage Solar Charge Controllers. I suspect that the PV startup voltage is higher than the 120 V minimum MPPT voltage, and higher than your 135 V.

On 2021/01/25 at 7:09 PM, Beejsteri0us said:

I am wondering if the PV panels are connected properly or if I need more than 3 panels? I was planning on getting another 3 panels hooked up in serial then paralleled together with the other 3.

No, you would need to put all 6 in series. Maximum MPPT voltage is 450 V for your model, so you can run at least 10 panels in series, probably more. Putting another 3 in parallel with the existing 3 (to end up with 3S2P) would not increase the voltage at all, and the low voltage is likely to be your problem.

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Thanks! I attached another 390W panel today in series with the other 3, totalling 4 in series now. It’s operating as it should now and I am registering DC to the inverter, but clearly you are correct, I need more panels. I will be adding another one to the string this week which will give me 5 x 390W power.

Thanks for the feedback! Greatly appreciated!
 

Another question: I am getting a light buzzing noise from the alu frame of one of the panels and it’s reading 12v with my volt meter... is that normal?

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On 2021/01/26 at 11:21 PM, Beejsteri0us said:

I am getting a light buzzing noise from the alu frame of one of the panels and it’s reading 12v with my volt meter... is that normal?

12 V from the frame with respect to what? DC or AC?

I note that on these high voltage SCC models, there is 230 VAC (half wave) superimposed on the PV terminals (with respect to earth). The PV cells have some capacitance to the frame, so the frames need to be earthed properly for safety. The current in the frames and earth wire will have a fundamental of 25 Hz I believe, and the half-wave nature of the waveform will give it a raspy buzz if there is any magnetostriction happening.

Perhaps more likely, there could also be slight sparking happening if the various connections aren't tight, and that arcing could be audible. You might even be able to see the tiny sparks if you can shade the area well (not permanently, obviously 😃). Be safe with that sort of work. Obviously, any voltage high enough to cause an audible spark is high enough to give you at least a nasty belt, possibly worse.

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