Series string voltage dropping to 1/10thunder load

[ericfx1984]

I have a series string of four 250 w San tan solar panels

Every now and again.. usually after a few hours of heavy use I noticed that this string seems to drop in voltage and of course output in general

Typically I see somewhere between 130 and 140 volts but today I looked and it was reporting as 14 volts and I thought surely that was just an error so I took out my voltmeter and tested it at the input side of the breaker and sure enough it was reading about 14 volts

I shut the breaker off and checked it again and it was back to a little over 130 volts

I checked everything else disconnecting a few connections and reconnecting them and still right around 130 volts.. I turned the breaker back on check the app it was right around 130 volts then drop to 105 still pushing out nearly 35 amps to the battery

That was in a couple minutes it was back down to 14 volts.. I'm kind of wondering if there's not a bad panel

 

[RCinFLA]

PV panel is an illumination based current source not a voltage source. Its maximum voltage is clamped by the number of series connected cells inherent diode (this is Voc)

If an MPPT controller cannot determine a solid MPPT point, perhaps due to poor illumination level or random shading on array, but it measures PV voltage output above battery voltage it usually reverts to PWM mode. The panels will drop to near battery voltage if controller drops to PWM mode. If you have a 12v battery, in PWM mode, the panels will drop close to the 12v battery voltage level, regardless how many panels you have in series..

 

[Bud Martin]

Did this problem just start?
If you have bad connection that develop high resistance when high current start flowing I would do close inspection of all the connectors.
I do not know what kind of SCC you are using, Can you run just 1 panel at a time and see what will a happen, or may be just two in series at a time to help narrowing down the cause of the problem?

 

[ericfx1984]

Did this problem just start?
If you have bad connection that develop high resistance when high current start flowing I would do close inspection of all the connectors.
I do not know what kind of SCC you are using, Can you run just 1 panel at a time and see what will a happen, or may be just two in series at a time to help narrowing down the cause of the problem?

I'm using a EPEver 6415AN

I have two other series strings each on there own charge controller that are pointed the same direction that are not doing this..

although this particular series string is literally sitting on the ground and propped up by cinder blocks whereas the other ones are on top of my RV they're oriented the same direction and have a similar tilt

It is later in the day that I'm noticing this I'm going to watch the panels a little more closely tomorrow assuming that the Sun cooperates

I mean by the time we hit four or five the sun is extremely toward the west this time of year so it may well just be dropping out of MPP

 

[travisandblair]

I am having a similar issue and I can't seem to troubleshoot the problem. My system is exclusively for a detached shop I am trying to run off grid. LVX 6048, 48v Trophy Battery, SanTan Solar used panels 240W 37.2 VOC 2 parallel strings of 10 in series run through a branch connector. At night I don't have anything powered up that can consume electricity except for 1 power strip that has an LED light and a USB converter built into it. Everything else is either unplugged or turned off. I understand the higher consumption rate of the LVX 6048.

(Disclaimer - all of this troubleshooting was done in full sun with no partial shade)
I had the solar panels temporarily on the ground for troubleshooting until I fine tune the system. Everything seemed to be working fine until I went out and my battery was at 32% SOC one morning and not charging even though the panels should have been producing enough power to charge a little bit. (The input on the LVX showed 295V and 516W input from the array). I started troubleshooting panels and found that each array was indicating on a voltmeter 330Vdc. I went to check the resistance and sometimes it was 0 ohms and sometimes it would not register (indicating there is no continuity through the panels). I started checking each individual panel, including pulling the covers off of the back of the panels to check the diodes. Sometimes the panels would have 0 ohms, sometimes not registered. All of the panels showed approx 33 Vdc through the panel though.

I tried to isolate individual strings, and eventually ditched the branch connector to wire just 1 series of 10 panels directly to the LVX and immediately got 330 Vdc and 2kw input showing on the LVX. The battery started charging up with over 30 amps, and things were looking good.....Until a few hours later when I went back out and the battery stopped charging at 78% SOC and the LVX showed back to the 250V and 500w (fluctuating). But the sun condition was exactly the same - full sun, no shade, no load change, etc. I am very frustrated.

I already had problems with 1 LVX 6048 and had it replaced by Ian at MPP Solar US (he did an awesome job with customer service btw) and I hate to bug him again. Especially if I can't tell if its my panels, the battery, or what.

I am about to throw the whole thing in my pond and wire up my shop from the house.

Please help if you can.