Really need the data sheet on panels and controller.

SolarFennel250 (4).pdf3pall_DIG & 3phbcDIG inst. sheetWHITE COVER .pdf

I'm new so I hope this works!

I feel the charge controller is absolute junk it rated for 200 amps but it's more like 40 amps @ 24 volts anything over 40 amps and they burn right out with in a couple of days I just put a new one in a week or so ago and the thing gets so hot it will burn you and I work on hot car's all the time. I think it need a better heat sink and a fan. But if you modify it would void warranty.

first time solar math
I did the math once and it came out to be
38 volts - 10% for fall off in the first 15 years = 34.2 volts
38 volts - 20% for fall off in the first 25 years = 30.4volts

But at the rate they are falling off i'm at 34 volts in the first year.
When the system was first set up it was putting out 38 volts at 64 amps = 2432 Watts as of my last good reading last week we are at 34v x 17 amps = 578 Watts

What is the Voc of each panel? Measuring it at noon isn't the best idea, especially if they were already generating that day. Voc is not sensitive to the amount of sun (as long as there is a little bit), but is fairly sensitive to cell temperature.

V "under load" will match the battery voltage if you have a PWM type charge controller. 28 V is a pretty reasonable value for a 24 V battery in the bulk stage of the charging cycle. From the documentation you linked, I can't tell what specific CC you are using.

The 34 V x 17 A that you reported looks like nonsense. Power is not calculated from Voc and Isc. Voltage and current under load is what matters when tracking your generation, but when charging batteries, the values you see may be a function of the charge state of the battery, and not an indication of what the array is capable of generating.

Nothing you've posted yet is convincing evidence that anything is wrong.

So I should be testing under a load. It's not a PWM charge controller. It's a solenoid type charge controller. It look just like a beefed up ford firewall mount starter solenoid. How much of a load should I put on the system to check it? I should have 1,750 watts at noon from the panels feeding into two super start platinum AGM batteries with 70Ah that feeds into a Aims 6k inverter with 18k surge for motor start ups.

My issue is when we set up this system it ran my home by itself no problem now I can't even run a little 600 watt heater I have had two solar tech teams come out and look over the system one being zuercher electric company and the other solar solutions rated by Solar Power World, the industry’s leading business-to-business publication, 2015 Top 500 Solar Contractors List. the other spent two days looking over the panels and both companies said it's the panels. all three of us are getting the same readings of 34 to 35 volts and 17 amps with no load and I completely agree it makes no sense at all because the diodes are only rated for 15 amps I think. something even more confusing is if you test one panel with no load it's 34 volts and 17 amp and when you parallel them all together you get the same reading from all the panel at the combiner box.

So let's say tomorrow It's a good sunny day and I take a reading where should I take my reading from and how much of a load should I try and put on the inverter to get a proper voltage and current reading from the system?

+1, something is fishy, we need to double check that, in other post you say 17A no load, solar panels only put out current under a load, so I think you mean no load off of your batteries, but something is pulling current or you would not be able to get that measurement, how and where are you getting that measurement?, just check the open circuit voltage and short circuit current of each panel with it temporarily removed from everything, then you go from there. The panel voltages need to be checked at each panel first then move down the line, if they are being measured at the combiner box for convenience that could be part of the problem, it doesnt take much of a bad connection, etc. to drop 2v.

P.S. How far from each panel to the combiner box?

OK, the picture you took is of a voltage triggered relay. From what I can see the 28 V under load you are getting is exactly what it is designed to do. Even if the panel voltage had degraded, it would have zero consequence in this system because it does not operate at the panel's maximum power point anyway.

You may be able to get some help here, but understand a couple things:

1) The system is really not very good, and was probably a waste of money.
2) The panels are probably perfectly healthy, and only your misunderstanding of how PV works is leading to your angst.
3) Your batteries are probably dead from mis-use.

If you can accept these three things as fact and still want to figure out how to move forward, we can start over and figure out what you should have bought to begin with.

I went with a off grid system because we get snowed in and lose power for a month at a time in winter. This is why it is so important for me to get this system backup and running correctly.

I do take my measurements from my combiner box most the time but when I do I pull the disconnect between the combiner box and charge controler. I also have permanent voltage meters set up at the disconnect pulling readings from the solar panel side and another voltage meter pull a reading from the battery bank. could the meter taking reading from the panel side be enough pull on the panels to cause them to read 34v? I think when I bought the mc4 cable I bought 100ft but after making my wiring harness the longest length of cable would be 20ft from solar panel seven and six to combiner box. total length of wire from the farthest panel to inverter 40 feet of wire. it also changes though in wire gage we start off with mc4 then we go to 4 AWG and then to 2 AWG. I should just try and draw a blueprint of the system I think it might help. I just pulled the disconnect between the charge controller and combiner box it's 12:56 noon here and cloudy battery bank shows 25.2 v and holding good. Panels side is 34.1 v but will get worse due to heavy cloud cover moving in. What really had the second tech crew stumped was the first and second day they came out they got the same readings with completely different weather one day almost no light dark dark clouds almost like a cloudy night and the second day clear blue skies. That crew also mentioned the possibility of a voltage leak but were unable to find it.

Batteries are good but I am open to ideals at this point! I went with a off grid system because we get snowed in and lose power for a month at a time in winter. This is why it is so important for me to get this system backup and running correctly.

If they were testing the panels under no load to see if they were within spec that seems normal. Solar panels are a current source (amps), the voltage usually varies only slightly under no/low load conditions, but can bog down and drop quite a bit if under heavy load for the amount of illumination it is receiving, the difference between cloudy and sunny will make the current (amps) vary greatly, but the voltage not so much.

The controller appears to be an inexpensive model and not MPPT, so as someone else mentioned it cannot effectivly utilize any voltage above 28v in your current system.

Switching to an MPPT CC will not necessarily help with Absorb stage, but it will give you a minimum of 50% more current during Bulk with no other changes.

Doesn't float require less current?

How would you correctly test a single panel while pulling power from it?

I disconnect all the panels except one. The one I want to test and I put my meter probes into the other socket on the mc4 branch connector to test the volts and amps pulled by the charge controler to the batteries from one panel.

Now when I seen the retailer test the panels the directly probed the mc4 connector from the panel for voltage and then they connected positive + and negative - together and used a clamp type meter to test for current.

Now I don't really know a whole lot about solar just what I have picked up from other but I would think going positive to negative would cause power to build up in the panel and would not give a real reading of the panel under load.

P.s please feel free to correct me this is a learning experience for me.