Sol-Ark 15K: A string suddenly has voltage at night, produces power much later

[samus250]

Hello!

I have a Sol-Ark 15K with two strings connected, one in M1 and the other in M2 (so I have an empty module). I have 4 rows of 6 panels each, 24 panels total, each with a Tigo module. IIUC (I didn't install this myself), the first two rows are connected in parallel into M1, and the second set of rows are in M2 (so 6 panel in series, two sets of 6 in parallel = 12 per string). All panels are pointing towards the exact same direction, but the first two rows (M1) are at a very, very slightly more upward angle. Other than that, M1 and M2 are pretty much exactly the same. I would notice a very slight difference in power output, e.g. M2 would produce 100W more than M1 during the day, M1 would produce 100W more than M2 during the afternoon, but everything was pretty much normal. In fact, sometimes this would pull more than the 10kW total rating, I've even seen 11kW. The Sol-Ark 15K even reaches the 26A limit sometimes, so performance has been pretty good.

Things would normally look like this, e.g. on Sept 14:


M1 would sometimes get the bump to 200V+ a bit later than M2, e.g. on Sept 18:


All of a sudden, this is happening. It started happening on Sept 21, this graph is Sept 30:


Notice how M1 shows ~50V during the night, and the voltage kicks in much later during the day. Current stays at 0 until everything kicks in. However, once it does, it behaves pretty much exactly the same as M2 until the Sun sets. This has happened every day since.

Another example, on Oct 1:


Has anyone seen this before? I've contacted the installers to take a look. They acknowledged me, but we haven't set up an appointment yet. I haven't contacted Sol-Ark yet. I wanted to share here to see if anyone has seen this before and might have any helpful information or ideas of what could be causing this.

Thanks!

 

[#40Fan]

First thing I would try is a simple reboot.

 

[samus250]

First thing I would try is a simple reboot.

Well I guess that makes sense, don't know why I didn't think of that. Even washing machines need to be rebooted once in a while nowadays.

I'll try that at night to not disturb the output (I might not be able tonight though, but will do soon and I'll report back). I've never had to reboot this, so is there any specific procedure? I have a pass-through set up so I'll connect the house directly to grid while I reboot. I also have a HomeGrid battery, can that just stay powered on? Do I just cycle the Sol-Ark's On/Off button, or is there a reboot option in the menus somewhere?

 

[Oldphile]

There's a power cycle sequence on page 23.

 

[samus250]

Update: I did the power cycle, it seemed to have improved, but for just under a week. Same thing happened last night: M1 suddenly shows 100V at 10:00pm, voltage stays high, and in the morning it started producing 3 hours after M2 did.

I contacted the installer to help me for next steps. Our plan is to leave everything alone and just swap the string from M1 to M3 (which is empty right now) and see what happens.

Any other ideas of what could be happening? Any insights are greatly appreciated! If M3 works fine, then I guess I'll have to start communicating with Sol-Ark to get M1 fixed or something.

 

[#40Fan]

It does sound like you're on the right track for diagnosing the issue. I'd go ahead and shoot Sol-Ark an email and see if they have anything to say. Could be something as simple as an update that is needed. Rebooting and swapping strings will also help them with figuring out the problem.

 

[samus250]

tl;dr: a projectile hit one of the panels on the string and that was the cause of the observed power output behavior.

Long version:

So I forgot to update this thread. The installers switched the string from M1 to M3 and it didn't work 100% either. I mean, it did work 100% some days (including the day just after the switch was made), but other days it would kick in many hours later as seen in the graphs in the original post https://diysolarforum.com/threads/s...t-produces-power-much-later.70184/post-887630. For the past week, it just got way worse... M3 produced zero energy in an entire week.

For many reasons, it's quite difficult to access the roof, and the panels aren't visible at all from the ground. We finally had the chance to check the roof and it turns out that one of the panels in that string was hit by a projectile and cracked. I'm guessing rain would soak and it would be in some kind of electrical fault until it evaporated and got dry later in the day.

It's weird cause I remember specifically making note of rain patterns and it didn't seem like it was affecting the output at all, but maybe it's not just rain, maybe dew could regularly cause it too. However, when it did kick in, even if it started raining later, the string would still output at what seemed to me to be full power for the rest of the day. Who knows? What I do know is that taking off that panel from the string fixed things.

 

[robby]

I started to read the thread and I noticed that in the Mornings you had some voltage but no current from the string. Then at peak hours the Voltage shoots up and so does the Current. My first thought was that you had a loose connection in the wiring and it was heating up and making contact during peak hours.
The really baffling part was the 50V at night. I am still not sure why it was reading that. Even with a cracked panel it makes no sense.

 

[Texas-Mark]

he really baffling part was the 50V at night. I am still not sure why it was reading that. Even with a cracked panel it makes no sense.

Perhaps when it cooled off at night, the panel crack actually created an open circuit and thus there was some sort of "floating" voltage originating from the CC.