First post, long time lurker. I have a 18kpv inverter, I have 1 pv array attached to pv input 2, the array outputs around 500v and has been working fine for 3 days. This morning, about the time the sun began hitting panels I heard loud popping in the inverter and smelled an electrical smell, no smoke though. When this happened, it switched back to grid power. After this I switched off pv input, but it would not switch back to battery discharge. I turned off power backup mode as I was testing off grid mode to reduce tiny grid export spikes. After this the batteries would charge using pv, but the voltage would drop and after 20 seconds or so it would be below the 100v and switch off relay it then reset and had 500v which then reduced again until relay cut off, so you have any idea what could cause this issue? The pop was very loud BTW, it was not just the standard relay clicking
[SOLVED] 18kpv loud bang on day 3 of operation
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LithiumSolar
Solar Enthusiast
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I would immediately shut that off and disconnect all power sources. Contact the place you purchased it from if it's still under warranty. I would guess either 1) a capacitor blew 2) a relay got stuck somehow and sent power where it shouldn't have.
Yes to this, likely cap blew... VOC of pv?
How many panels in series and specs?
Thanks, I was thinking capacitor but didn't want to do any surgery before taking to support. But it's shut down now for sure and back on grid... always happens on the weekend, but planning to give signature solar a call tomorrow. Just not confidence inspiring for a new unit and that no faults happened
LithiumSolar
Solar Enthusiast
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Good thought on the PV voltage. I see you're in the US, don't know where specifically but some areas are seeing excessively cold weather. Did you account for the voltage spike in the early morning?
Edit: It looks like the 18KPV lists 600VDC as the absolute maximum.
Edit: It looks like the 18KPV lists 600VDC as the absolute maximum.
Running the q cells 405w got 12 in series. It was frosty and cold this morning, but no where near cold enough to have these things come close to 600v DC, they were outputting around 505v, I interpreted this as ok to exceed 500v, but understand thus is max usable voltage. I may reduce to a string of 11 panels if this is deemed to be part of the problem. When I finish my other panels I will have both connected to pv1 input to parallel in unit and may have a smaller string of around 6 panels on one of the other inputs. I have a wire run of about 300 ft, so I need to run voltage on the high side.
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It is pretty cold for us im south carolina. We rarely get below freezing. In the mid 20's this week. I sized the array for - 11C based on the calculator for my region and thermal coeff for extreme min temp. At this min temp point, the max Voc should be around 590v. I figured if it ever got that cold and was absolutely bright and sunny I would shut them down, but again the risk of full output and these extreme temps seemed quite low to me. There was frost on panels today so I don't know how that would affect them, but would assume just like clouds. The data history never showed any pv voltage above say 500v and I measured with meter and it was rock solid around 505
What was your morning temps there today?
Edit... Ah, I didn't see your reply to temps above...ok. Your VOC is within limits.
Best bet is to contact EG4. Sorry about it.
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Called signature solar, but because I'm out of town they wouldn't even talk through any of the data history with me until I'm in person and the unit is online...so guess I'll have to try to get them on saturday next weekend...hoping they are a bit nicer and more willing to help in person, but we shall see...in the meantime, if anyone has any epiphanies feel free to share, thanks everyone, I will keep updated on progress
Solar Guppy
Red Cobra Guppy
You don't list your location, but using an online calculator shows your going to close to exceeding the inverters never exceed ratings
You have 12 panels in series rated at 45.34V at 25C ( 77F ) if in the morning you have 0C ( 32F ) the string will be at 580V.
So you need to reduce the number of panels in series it would seem
You have 12 panels in series rated at 45.34V at 25C ( 77F ) if in the morning you have 0C ( 32F ) the string will be at 580V.
So you need to reduce the number of panels in series it would seem
jorby
Solar Addict
Yeah, 580v is too close for me. I have 12 series @42voc / 25 deg c. =504voc x 1.0675@ 0 degC = 538voc. My 18kpv didn't blow up with frost on the panels the last 3 mornings. My experience with new, high-voltage electrolytic capacitors, is that they might draw more current than they should at maximum rated voltage while their electrodes finish forming. If the capacitors are rated 600v, it would be foolish to rate the input that high in my experience-based opinion. I hope they are rated higher than 600v and that he just got a, hopefully rare, bad one. The pucker factor made me self-derate by another 50v. I would like to know the actual capacitor voltage rating, but that pesky anti-tamper sticker keeps me from looking inside.
There probably isn't much they can do without it being online and you being there to go through it with them. Hard to troubleshoot anything otherwise.
How cold was it Sunday morning where you are?
It's 315V in 2s so there's some headroom....I would like to know the actual capacitor voltage rating, but that pesky anti-tamper sticker keeps me from looking inside.
Heat gun is your friend for the sticker
jorby
Solar Addict
Thanks for the photo. I saw 315v in the first picture you posted and thought that they might be using pairs for 630v. Only 25v headroom on each capacitor. I would love to see how they keep the voltage balanced. I have done it with 450v caps in a 5kv supply. Every one of them was checked for leakage current and then they were put in parallel and the voltage was slowly increased over time until the leakage current dropped off at 450v. I don't think they would go to the trouble to do that in a production environment. I used 12 in series, for each of two parallel voltage doublers, each driven by 3 microwave oven transformers. You can see the bleeder resistors in the photo below. They help keep the voltage equal at around 416v each, and I actually checked that they were all staying within a few volts. Output (capacitor) voltage is regulated by phase firing 3 primaries in series on each side, with the two sides are out of phase. Bridge rectifier is used as 2 half wave rectifiers feeding the doublers. 6kw@5kv output. The wood box hums very loud at full load.....It's 315V in 2s so there's some headroom.
Heat gun is your friend for the sticker
View attachment 260179
Oh wow, I need to know, what the heck do you use that for? Plasma cutting something? How long does the bank stay charged after power cutoff?? Thats some lethal stuff!!!
Quattrohead
Emperor Of Solar
Nice derailment, cool shit 
Thank you for the response. I think yes it would probably be best to reduce the string size as a safety net. I didn't use the same calc, but I got similar values. the extreme min temp in SC I used called for -11 C in my area. Although like I mentioned, sub freezing temps are pretty rare. this temp would be 12 deg F, which I can only remember once or twice in my life. in any case, my calcs showed 593 at extreme min for Voc, obviously dangerously close to never exceed voltage, but in my mind I just can't see sizing with one less panel to account for extreme min temp, with full sunlight, and full voltage output from panels. Maybe I'm naive, but just my thinking, and if weather was ever marginal, the pv disconnect is always there.
in my case from morning of 12/1 that caused the issue, I know the voltage never exceeded the max both from data logging and physical measurement with a meter. I saw 515v pretty steady with the meter when troubleshooting after the "banging". Signature didn't offer me much as I mentioned bc I wasn't in front of the unit, but they suspect MPPT 2 may have shorted and that's the first thing I'll check when returning home.
This is the data from 11/30 when I was fat and happy and seeing my new install work flawlessly, the temps were almost identical (low of 29 F / -2 C )
and the data from the morning it went "bang", the spikes later in the day were me troubleshooting, and the final spike in pv2 voltage is with one panel removed from the string.
the morning of 11/30 was bright and sunny, the morning of the failure was a bit more haze, but still some sun, and pretty thick frost on panels.
it was 29 F low, so about -2 C; voltage was around 505 peak measured with meter and with data history from inverter
Those voltages are Vmp, not Voc. Measure it with the string isolated at similar temperature and see.
I understand, Voc is worst case and used for calcs and sizing, but why would I care more about Voc than the voltage actually being generated to inverter and with load for real world? the margin is still 10 deg C at this temp with full direct sunlight. so all I'm saying as regardless of my string sizing being potentially too close to max for comfort, the unit did not see anywhere near 600V in this case so it doesn't lead me to any answers
robby
Electronic Engineer
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Is that a power supply for an HF Tube Amplifier?
CaliSunHarvester
Solar Addict
A year ago I did not know about the temperature adjustment etc, and in a thread here somewhere someone explained to me that as part of the mppt process (optimizing), briefly Voc will be on the wires. Something about MosFETs switching and in the switch process, voltage rises from Vmpp to Voc.
I don't know if that happened but you would probably never catch that with a multi-meter.
zanydroid
Solar Wizard
I hope this is a rhetorical challenge for an explanation…
If the FETs switch off and stop drawing current for any reason, your solar panels by definition would be Voc
There’s no guarantee that the MPPT will keep the FETs switched on enough to keep you below
Simpler example. Suppose the battery is full and you have an off grid system, or your grid connection trips off so excess is not sent to grid. The FETs will switch off because there is nowhere for the juice to go
Or. The firmware has cases where it turns off PV production for whatever reason
Also, Vmpp is compared against the MPPT operating range while Voc is compared against MPPT max input voltage, on the spec sheet
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