[Solved] Why does my Growatt SPF 5000ES reject all PV input?

[Offgrid Aussi]

With solar panels connected, I can measure only around + 1.5V DC at the PV terminals in the middle of a sunny day, although the unconnected open circuit voltage of the array is 400V (Voc) and the short circuit current is around 8A (Isc). I measured both, just to be sure.

The Display of the inverter tells me that I'm getting exactly 0.0V out of my panels, which I can confirm. There is no grid or load connected, just a 48V battery with SOC 98%.

While the inverter was running idle like that, I disconnected the main PV isolator and could hear and smell the spark it trigged inside the isolator. As if there was some serious load to disconnect.

I then disconnected the battery, waited 24h reconnected everything and rebooted the inverter, but no change there. I did some more tests and found something that struck me as odd, but could very well be by design:

When I start the Inverter with no PV input connected, I can measure a DC current building up across the PV terminals. It starts at around -1.5V and creeps down to -24.8V within a minute or so. Then it stays there. Just an observation, I have no idea whether that points to a fault or if that is desired behaviour.

I do know, that I don't know where to go from here. I certainly don't want to stress my PV isolator like that again, but I'd also like to get the PV array connected.

Has anyone encountered a similar problem when connecting the PV side of an inverter?
The manual reads like PnP: Just connect the solar array to the PV ports and start the inverter. As long as the input voltage is between 150 and 450 V DC, everything should be fine.

Well, in my case it's not, so any help is greatly appreciated.

 

[kommando]

Seems to be the same issue as

Growatt 3000 LVM won't recognize PV input unless restarting unit?

What would be the possible reason - I have a 48v system and PV input showing at 92V. Whenever I disconnect PV input, or after a night, Growatt will no longer recognize solar input. Disconnect/reconnecting PV cable does not help. Also, the switch in the Growatt does not fully shut off the system...

diysolarforum.com

I would send it back as it seems to be a new purchase and get another makers inverter.

 

[AntronX]

check PV polarity. sounds like you connected positive and negative of solar array backwards.

 

[Offgrid Aussi]

@AntronX: OMG. Please forget I ever asked.
I did not think I could get this wrong, but I surely did. My SunnyBoy had plug terminals, so I never thought about the polarity of solar panels much and since the battery terminal right next to it is red for - and black for +, I just assumed it would be the same. Just an explanation, no excuse.
Fortunately my stupidity did not fry the inverter. Everything seems to wok fine now.
Thank you heaps for that, it really makes my weekend!

@kommando: I had the same thought, but from what I know now, I'd say that in Relay's case the lower voltage threshold might not be met to start the PV intake on cloudy days or in the mornings. I do not know about the 3000LVM, but according to the manual my 5000ES needs upwards of 150V DC input to get going.

Thanks again guys, I appreciate your support!

 

[AntronX]

Awesome! Two clues pointed towards reverse polarity problem. First was 1.5Vdc at the PV terminals which happens to be forward voltage drop of silicon diode under heavy current. Inverters usually have those to prevent damage from reverse polarity. Second was when you "disconnected the main PV isolator and could hear and smell the spark it triggered inside the isolator". That right there means that the voltage snaps back as soon you break contact and causes a decent spark so the array had voltage and current available.

 

[Offgrid Aussi]

Makes sense now. Even to me. Thanks again.