Beginner Help with an Interesting Situation

[cstitz]

I has a system installed on our van, and while in the process the installer accidentally installed two 210 watt panels instead of one. So they claim that they didn't hook it up, and want $700 to hook it up. However, it seems to me that the panel is hooked up and sending power to the charge controller. But the battery isn't receiving the charge, rather half of it. Can anyone help me diagnose what's happening here? I sincerely thank anyone that can help me out, I've been trying to figure this out for a while.

2 x 210 watt flexible panels on roof
Renogy MPPT charge controller
Victron Battery Monitor
100 amp Battleborn battery

Here's the summary video of the issue. https://photos.app.goo.gl/K8hCAiW5gzrgKvvz5

Power Output = Claimed Wattage x the cosine of the sun angle. So in this instance, using the sun level site: https://gml.noaa.gov/grad/solcalc/azel.html 52.94 is the sun angle, cosine is .79 so .79 x 420 watts = 331 watts, again we're seeing half that and can account that small difference to some hazy clouds. The thing that confuses me can be seen in the video. Both panels are providing power to the charge controller. You can see the power it's receiving in the screenshot. But it's only outputting about half of that.

So, where is the charge being cut in half? From 215 to 118? It seems to be reaching the controller inside. Is the controller "throttling down" the output? All settings for the charge controller and the battery monitor are below.

 

[robbob2112]

Hi,

So couple of questions first -- Are the panels wired in series? If so covering one of them would tend to choke off the power from it and make the string bad --- but from your example where one panels covered cuts the power in half I assume they are wired in parallel ---
you should be able to examine the connections from the panels up there on the roof and see if they have a pos and a neg from each connected to the wire heading down which would be in parallel. Or if the panels are connected together in the middle and the pos from one panel and the neg from the other panel heads down which would be series.

There is a free program out there https://drawio.com that you can use to make a diagram of what your system is. Takes about 20 minutes to learn to use.

They are both hooked up for sure from your video so no idea what they would be charging you that kind of money for doing --- I suspect you were way over-charged for what you got, but can't say for sure...

They sold you a battleborn which is mostly hype and marketing....and VERY expensive for what it is ... the common cheap batteries these days perform as well and if they go south after the first month you just replace.... but for the most part they work or they don't ... and if they work they work for years.

What is the model number of your MPPT? it should be printed on it or possibly in some of the paperwork the installer gave you.

Also, what is the model number or specs of your panels -- if you can get to the back without dismounting there is a sticker - otherwise there should be paperwork telling enough to look up the specs.

What is the model number and size of the inverter?

What size battery was installed? 12.8v100ah or some other size?

One comment - panels mounted flat tend to only put out 30% to 50% of the rated power --- Any clouds or haze kills that as they pass --

Using pvwatts and a tilt angle of zero with your panel size and them as thin film -- in full sun they should generate around 280W -- I suspect a bit less and on a cloudy day about 1/2 of that ---- so you might be getting what is right and that is all it does.

Answer the above questions and I can calculate if the amount of panels you have is sized correctly for the battery and inverter.

 

[LakeHouse]

Power Output = Claimed Wattage x the cosine of the sun angle.

I see what you're trying to do here, but this just isn't how it works. Lots of other things affect this. Temperature, shading, clouds (even if they aren't actually blocking the sun), haze, etc. Even latitude has a bigger effect than you're accounting for because the sunlight has to travel through more atmosphere. Also, flexible panels are, uh, not great. I don't have any experience with them myself, but they have a bad reputation here on the forum.

Your experiment does seem to indicate that both panels are probably providing some power, and they're definitely both connected to the SCC. Although are they connected optimally? That's harder to say and we'd need at least a little more info. Specifically the panel specs, Voc, Isc, Vmp, and Imp.

You can see the power it's receiving in the screenshot. But it's only outputting about half of that.

There are three options for what's happening here, and I'll list them from least likely to most likely:

1. The SCC is drawing 215W from the panels but somehow only sending out 118W. This is very, very unlikely because that extra 97 Watts has to go somewhere and the answer is always heat. Your SCC would be red hot in a few minutes and eventually on fire.
2. The SCC is lying to you. Maybe not on purpose, of course, it could be getting some sort of bad reading from somewhere. I think this is unlikely; it's power measurements in and out at least sort of line up (26.7V * 9.4A is about 250W), so this doesn't seem to be the mystery we're trying to solve.
3. There's something else drawing DC power. This is almost certainly the answer. The SCC says it's sending 215W to the battery, but all it really knows is how much DC power it's sending into the 'system'. Likewise, the battery monitor (assuming it's installed correctly, anyway - lots of people get those wrong) only knows how much power is going into or out of the battery. In between the SCC and the battery monitor, neither of those devices know what's happening.

 

[cstitz]

First of all, thank you both for the quick and thoughtful responses. A bit more detail first, and I'll try to answer all the questions succinctly so as to not get bogged down. This system has been installed and running for 3 or 4 years now. We are not working with the same person that did the original system install. The new panels were installed because we put a pop top tent (Super Pacific Cloud Cap) on top and wanted something more sleek for the solar installation.

I'm almost positive there's nothing else drawing power. I failed to record it, but I had the solar disconnected right before I started the video, I was drawing like three watts or something which I think is just the battery monitor, the little lights on the USB chargers, etc. Nothing in the van was running, it's a pretty simple installation and the only power draws are easily accounted for. Fan, cooler, gas heater, lights, inverter, USB chargers, none of them were on. And if there were some sort of 100+ watt vampire I would notice it in the mornings but the battery doesn't deplete at all overnight.

The panels are definitely installed in parallel.

The Battleborn has been working great since install years ago.

Charge controller is the Renogy DCC50S. (this is new also because the new panels pushed the voltage past the limit of the old charge controller, the previous model of the same DCC50S)

Original panels were 2 x HQST 100 watt panels.

New panels are 2 x Artex 210w flexible wired in parallel.

Inverter is AIMS Power 1000 watt inverter.

Battery is 100 amp hour.

Panel specs: Maximum Power: 210 W, Voc: 39.8V, Isc: 5.30A, Vmp: 35.60V, Imp: 5.86A, Maximum System Voltage: 600VDC

 

[LakeHouse]

Charge controller is the Renogy DCC50S. (this is new also because the new panels pushed the voltage past the limit of the old charge controller, the previous model of the same DCC50S)

I'm a little confused. That's not a solar charge controller (SCC), that's a DC-DC charger. Yes, it can be connected to solar panels, but why? What's wrong with an actual SCC?

Also, the specs say the max solar voltage is 25V (see below), and you're way over that. Which is bad.




My option #2, that the software is lying to you (unintentionally) is looking slightly more likely.

 

[cstitz]

Sorry, I'm sure I misspoke, I'm not up on the proper terminology. The Renogy charge controller takes power from both the engine alternator as well as the solar. Independently or together. The max solar voltage on the newest DCC50S is actually 50. Documentation is out there somewhere and I saw it before they made the swap, however the website os out of date. I was over on the old one at 25 and it errored immediately with the new panels, which caused it to not take any power from the solar, just blocked them out, only took power from the engine alternator. When they put the new DCC50S in it starting taking charge again from the panels.

So if the software is lying to me (that's fine) then do we think that the 110-ish watts that I was getting seems normal from those two 210 watt panels midday in full but slightly hazy sun? About 25% of stated wattage?

 

[robbob2112]

Reading over all of what you said I think things are probably working correctly for the hazy day.... So doing nothing until you see the results on a sunny day is a good idea...

we're it me I would leave the DCS50s in place to charge from alternator, but I would add a Victron MPPT... the 150/45 model.... then switch the panels to series...Just a change up on the roof... and mounting the new MPPT...should be able to just move the wires a bit in the bay where the DS50S this would give you an accurate view of the solar power you are getting...and switching to series on it with your panel specs would collect energy earlier and later.... and it would leave room to add another identical panel in series if you wanted.

 

[cstitz]

Thank you all. Waiting for the sunny day!