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Solar panel output low
#11
also could just be the connection and not the panel,cant remember who but they were having problems with those mc4? factory connectors
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  • RoamingKat (09-04-2018)
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#12
I will start with the simplest and keep checking till I find the issue.

I suspect that sternwake is correct and one or more panel is damaged from past behavior... namely having the panels disconnected in the sun last winter.

But, I can hope the problem turns out to be simplistic.
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#13
Smoking the diode(s) from disconnecting the panel in full sun under load ( feeding depleted battteries) is a possibility. It could just as easily be a connector issue.

i think it was Walkaboutted who found that her MC4 connector's conductive surfaces she had were not making contact within the connector.
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  • RoamingKat (09-04-2018)
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#14
How does one discover that?
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#15
Piercing the wire insulation and checking for continuity across the connector would be easiest, but piercing insulation is not wise, especially on solar cables.

One could disconnect MC4's, stick multimeter leads and read open circuit voltage, verify it is there, and if that same voltage is not on the far end of those mc4 cables near charge controller the mc4 connectors would be the most likely culprit, as opposed to the wire having broken inside the insulation somewhere.

This sort of diagnosis simply requires gettng up on the roof and some trial and error with tools and also checking at the wires entering the solar controller from the panels.

Simply shading the one panel or the other can at least narrow down the possible failure points.

Internet diagnosis can be frustrating for those trying to help.
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#16
Now I am baffled.

Morningstar showed ~10 amps at high noon. Then I put a thick blanket over one panel...the Morningstar then showed ~5 amps. Got the same reading (to be expected now) when I covered only the other panel.

I checked all the mc4 connections at the panels, combiner box connections, all the wire. Everything looks ok.

So, thinking maybe my batteries were “full” .... I put a serious load on the system .. I turned the inverter on and the AC on full tilt. The batteries were draining like crazy (battery monitor showed steady 120 amp draw). I left this run for about 5 minutes ... the Morningstar was showing that I was pulling ~ 15 amps. Shouldn’t the Morningstar be pulling everything possible to try to drive that load? If that Is true, then ~15 was all those panels had to give.

Shouldn’t these two panels be providing somewhat better 24 amps? Maybe as high as 30? They are 2 345watt panels...in perfect conditions I should ideally get 54 amps...so my reasoning says I should be getting somewhere around at least half that in September with the sun directly overhead.

Now I cannot figure out what the deal is.
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#17
Today, at 32'N with 198 watts, i am getting a max od 10.9 amps right around noon. June21 that is closer to 12.7 amps

So round up to 11 amps per 200 watts.

Not familiar with Lifepo4, and its voltage drop under 120 amp of load, but I imagine it is possible that the solar only had to make 15 amps to battery voltage at the maximum setpoint.

Lithium is said to have a very flat voltage curve, even with high loads, until they are just about at the 'knees' where it drops fast.

So What is your absorption voltage setpoint for these batteries? If 15 amps from solar is all that is required to hold batteries at 13.8v, then 16 amps might push 13.9v, which the controller is trying to prevent from occurring.

Again, i have not cycled Lifepo4 or watched their voltage through discharges, but I think that you need to be sure that their voltage is well below the absorption setpoint befire you can expect to see the maximum output from your solar controller, and perhaps a temporaty higher absorption voltage setpoint would make this more obvious.

but 120 amps of load should have drug their voltage down low enough, but perhaps not. IDK. no experience with em.
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#18
Sounds like the panels are working normally to me, unless they both failed by the same amount. 

Lithium batteries, when under load, don't drop in voltage as rapidly as lead acid batteries do.

It could be that the controller wont 'see' the substantial load until, and unless, the batteries begin to really drop, which will be later on in the discharge curve.

Does your controller have these two features:

1) PV voltage display

2) Battery voltage display

If it has PV voltage display, during your test, what did the PV (input voltage) display?

Was it being pulled down close to battery voltage (#2 above) or was it still quite high?

Solar panels will typically show a lower voltage as a load is applied, this is how they work. It means they are producing power.

If the PV voltage remained fairly high, it simply means they are not being called on to produce much power, since the batteries have not begun to drain to any large degree, at least in the 'mind' of the controller.

Possibly the 'custom setting' you mentioned in post #8 is not correct...or needs to be 'tweaked' a bit.
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#19
Sternwake and myself both suspect similar setpoint issues. 

Evidently we were typing about the same time, our posts stuck only about 3 minutes apart.

In other words, we both came to similar conclusions, more or less, at about the same time.

Worth checking into.
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#20
I will rerun the test looking at both the voltage and amp drain

I know that the Morningstar is set to hold at 13.8. I will watch the voltage as I run this test.

Thank you.
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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