Understanding how my solar system is working?

[JeffreyG]

I have a few questions on how my solar install is working. You can see the entire install in this thread:
https://www.escapeforum.org/forums/f...oad-21688.html

But in a nutshell I have three rooftop mounted 80W Lensun flexible panels, plus another 100W flexible panel that I can set up anywhere and plug in to an SAE port. The panels are all feeding an EP-Ever MPPT solar controller. I also have a shunt and Victron battery monitor.

Question 1: What kind of performance is normal?
My first few camping trips have been in November and March, and while system performance seemed low I chalked it up to low sun and cloudy days. So yesterday the E-19 was sitting under a perfectly clear May sky at noon and I checked the Victron battery monitor. Battery was at 72% SOC and getting a net 90W charge from the three rooftop panels. Getting 38% of the rated panel capacity seems low to me. I added the portable 100W panel and gained another 40W going in. I know the panels are not going to hit rated power ever, and there are losses, but still......what fraction of rated power is normal on a clear late spring day?

Question 2: Is my solar controller why I'm getting zero today?
So today is sunny and clear again. I went back out at noon and the Victron reports 86% SOC, and charging at 0W. I'm like, zero? I looked at the EP-Ever solar charger MT-50 remote, and it shows 0.8 amps, 20.5V, and the battery is 100%. I popped the breakers on the whole solar set, turned them back on, and briefly got 90W, and then back to 0W. Am I correct in surmising that the solar controller is not allowing charging because it thinks the battery is full? Why does the solar charger disagree with the Victron on what the state of charge is?


Bonus question: Could the solar controller have also been limiting input power yesterday because it thought the SOC was close to full? I'm thinking about trying to discharge the batteries to like, 50% or something and see what kind of solar power I get. In fact, I'm going to go do that now.


Thanks for your thoughts on this.

[JeffreyG]

OK, a bit more info. I just went out, turned on my invertor, and plugged in a space heater. I looked at the Victron to see what I was pulling (1000W) and noticed that the Victron has suddenly revised its opinion of the battery SOC. The Victron now agrees with the EPEVER, the battery SOC is 100%.

Hmmmm.....So more evidence that the solar performance is low because the battery is full.

Now, why did the Victron abruptly change its opinion from 86% SOC to 100% SOC? Interesting.

I'm going to run the heater for a while and see what the solar performance does.

[splitting_lanes]

You’re on the right path.

Running a big load will help to determine if you have a charger/MPPT issue.

I’ve run solar on my house for a decade, and if you’ve seen a peak of 38% panel output, that seems pretty low to me.

[Mike G]

Seeing the title of this thread, my first thought was, "Why does he want to know about astronomy?" You know, the solar system...