Solar panel/ charge controller issues? What to do?

Warich

Purchased 4-100 watt 12 volt Polycrystalline solar panels for our rv. Each panel is rated as follows.

Voltage @Pmp (Vmp). 18.6 V
Current @Pmp: (Imp) 5.38 A
Open circut voltage:(Voc) 22.6 V
Short circuit current  (Isc) 5.81 A
I have them hooked up in parallel.

They are connected to an Eco-Worthy 60 amp PWM charge controller.

The batteries being used are 4- 675 CCA / 845 MCA  (Reserve Capacity 200) group 31 deep cycle marine batteries hooked up in parallel using the correct parallel wiring diagram for such.

During the first few months of putting the system together everything was working perfectly with no charging issues what so ever.

Recently I have discovered the batteries are not fully charging at the capacity I believe they should be in the last few days.

When looking at the Eco-Worthy charge controller panel I notice  the incoming voltage is 12.84 volts with only 4.3 amps on a full sunny morning and through out the day.

It's been my understanding that the parallel wiring will produce more amps while keeping the voltage at the 12 rating area. I am not sure why my system is not producing at least 20 amps and only showing 4.3 amps according to the readout on the LCD screen for the charge controller. 

When I first hooked up this system in March of 2020 it was charging the batteries in full and going into the set float mode of 13.7 to which it was set. Over the last few days I noticed what I described above leading me to test each solar panel individually from one another. Testing resulted in 20.01 volts per panel with a few light clouds coming overhead. When connecting them all in parallel the meter shower 20.02  I use a cheap voltage meter and am not able to do am amperage test on the panels.

I then replaced all they Y connectors for the solar panes just in the event something was awry and received the same results. This indicated they was not the issue after re-testing.

Once again I looked at the charge controller and saw the same numbers as described earlier. Nothing changed other than less clouds and now showing 4.7 amps. I am stumped at what is going on as my batteries are slowly draining down on a daily basis and now into the 11.5 volt range and when charging barely making it to 12.1 volts and definitely not making it to the 13.7 floating charge through out the day. 

We are only using a small 1000 watt coffee pot in the morning for 12 cups, then turning it off once the brewing is done in 5-7 minutes.The propane furnace comes on 1 time every hour through out the night when it's below 68 degrees. Our light usage is about an hour each night with 1-3 watt LED string on the ceiling. All in all we use very little power and it seems there must be an issue that I am not figuring out. Or is it the charge controller having an issue and it's not showing any errors?

Any help would be much appreciated.

New_Mexico_Will

Since you have tested the panels, and they seem to be outputting the correct amount of power, the problem is likely the charge controller, but could also well be a loose wire connection.  Have you checked all the wire connections?  Specifically the wires from the controller to the batteries?  I think it's also possible that a diode may have gone bad and you are sending power back to the panels from the batteries, though that seems unlikely.  It might be worth adding some MC4 blocking diodes as a check, as they are inexpensive.  I think this is usually more of an issue with a series connection, however.  An easy test is to go out after dark and feel the panels.  If they are warm, this may be happening.  Regardless, I would suggest an MPPT charge controller.  It's not a huge difference with 4 panels in parallel but if you determine that the charge controller may be the issue, might as well upgrade.

Warich

I have checked all of the wire connections and replaced the MC4 connectors with the new spares that I had. Also have checked all of the wiring from panels to the Solar charger and to the batteries ensuring they are tight and connected as well as checking Ohm resistance values while wiggling each wire making sure there were no internal wire breaks. Everything has checked out. I will look into the MC4 blocking diodes as this seems like a great idea to help an unnecessary problem from taking place. I will take your advice on checking the panels in the dark to see if they are warm by chance. An MPPT controller will be in the making in the near future. Thanks for the heads up in a few possible issues.     

Photowhit

Well, I suspect it's just fall...

Other issues might be the marine batteries, which tend NOT to be true deep cycle batteries. How are they hooked up? It's difficult with 4 batteries in parallel for them to share charging and loads evenly. I would check them individually, have you been checking their specific gravity (SG)? I suspect 1 or more may be having an issue. If you would rather you could take them to an auto parts store and have them load tested. Do they have recessed caps like these?



So questions, how old is the system? sounds like just a 6 months or so?

What are your additional loads over the last month or so? just the furnace fan? Do you know how much energy your inverter uses? How much energy your furnace fan uses?

The voltage you see on the charge controller is the system voltage, it's the voltage that the batteries will take at their current state of charge. The charge controller should only regulate the voltage when it reaches your set absorb point. Can you check/change your settings on the charge controller or is it preset? Largely all a PWM charge controller does is regulate voltage. as the batteries charge the their voltage rises, when they reach the absorb point the charge controller limits the voltage to that point and the battery will slowly accept less current (amperage).

So basics of solar panels they tend to output  about 75% of their panel rating, this is called the Normal Operating Cell Temperature value. Some panels publish it, some just give you numbers to calculate it, but it runs about 75% of the panel rating. Much of this loss is in voltage, which is fine with a PWM panels as they are designed to be high enough to allow for this drop when charging batteries in their wheel house.

I mentioned Fall earlier... Fall effects charging in several ways, the days get shorter, right now we the sun is up about the same number of hours as it's down (the fall equinox) but more important than the loss of sun hours, is the angle to your panels, which I suspect are mounted directly to your roof. With the lower angle of the sun, you will have more shadows cast by your air conditioner, antenna, vents than you do normally. Even a little shade can reduce your solar panel to near nothing.

I'd suggest 4 golf cart batteries in the future. I think if you have difficult shading issues, a PWM charge controller is just fine, you may not have a particularly good one, but their are decent ones that are pretty reasonable.

I didn't ask if you had standard glass panels or plastic panels? Plastic panels tend not to last very long...

mcgivor

To gain a better understanding of what may be the cause there needs to be more information. 

At what latitude are you? 
What angle are the panels and what direction?
Is the system used daily?
Do you use the appropriate tool when disconnecting the MC4 connectors? 


It's not uncommon for a system to appear normal when the batteries are new and days are progressively getting longer, once the solstice passes, the hours of useful production begins to diminish  which will often go unnoticed until it becomes obvious.
For a 400Ah bank in daily use, a charging current of ~52A is needed, your array is better suited to weekend use when properly oriented, If the panels are mounted horizontal with indirect sun at a high latitude, the output will be significantly reduced.

To find out what each individual panel is producing in terms of current cover 3 at a time with a blanket or cardboard, each should have approximately the same current. Having 4 panels in parallel there really should be a combiner with individual overcurrent protection using MC4  Y connectors is not good practice.

New_Mexico_Will

Whats the issue with the Y connectors?  Too much amperage on the way out?  If it's 10 awg, isn't it rated for 30 amps?

Warich

Batteries are new in March 2020, wired parallel and balanced. They are recessed as in your photo posted with threaded posts. They have not been SG tested with a hydrometer. Assumed they were fine since being brand new in March 2020 when buying all of the items to build the system. I did check the water levels and all looked fine. I do have a load tester, but have not got to that point yet due to checking all the other issues first. I will be doing that in tomorrow afternoon when time permits.
 
Everything was purchased and installed in March 2020. The only loads have been use is a 1000 watt coffee pot for about  5-9 minute in the morning, then turned off and a single set of 3 watt LED lights. The propane furnace fan comes on during the night 1 time in most cases for about 3-5 minutes then shuts off when temps reach 68 degrees in the evening hours. During the day it is off. The fan is 12 volts rated @ 7.6 amps / 91 watts. The inverter uses 2 amps when turned on. It is only on during morning for the coffee pot and promptly turned off when brewing is done. There are no other items running off the inverter. 

On the Eco-Worthy 60 amp PWM charge controller I am able to change the float charge voltage. It is currently set at 13.7 as per recommendation. The other changes that can be made are the voltage on and off for over and under limits.

As for daylight time the panels have full sunrise to dusk exposure with almost no shading. The panels are mounted on a rail platform with about a 15 degree angle on the roof pointing almost directly south.. The rv is stationary on our property and used as a guest house. We have been trying it out for the last week or so to see what the limits are. Solar panels are glass.

46°56'30.8"N 123°18'27.7"W

46.941900, -123.307702

mcgivor

The 15° tilt, is that from horizontal? If so they should, at this time of the year be significantly more than that, use this calculator http://www.solarelectricityhandbook.com/solar-irradiance.html to find the optimal angle.

New_Mexico_Will said:

Whats the issue with the Y connectors?  Too much amperage on the way out?  If it's 10 awg, isn't it rated for 30 amps?

With all the panels in parallel with Y connectors if one were to fail then the remaining 3 could feed into it possibly causing a fire. This could be done if each panel has an inline MC4 fuse of correct value which is found on the specifications label on the back.

New_Mexico_Will

Solid point McGivor.  Those MC4 blocking diodes could fix that potential issue as well, if placed correctly. I'm a fan of the Midnite Solar combiner boxes.

Warich

mcgivor said:

The 15° tilt, is that from horizontal? If so they should, at this time of the year be significantly more than that, use this calculator http://www.solarelectricityhandbook.com/solar-irradiance.html to find the optimal angle.

The 15" tilt is horizontal and is due to the roof line of the rv already being tilted, but not known how much. Thank you for the calculator link. I will be using it and make sure things are on the up and up.

mike95490

A simple test, is at noon with panels in full sun, brew a pot of coffee,  that will present a load, and the charge controllers should try to use every bit of power from the panels.

BB.

If you are going to do more DC system debugging/understanding of how things work (car, boat, solar, etc.), a DC Current Clamp DMM (digital multimeter)--Really an AC+DC current clamp DMM:

https://www.amazon.com/UNI-T-UT210E-Capacitance-Multimeter-Resolution/dp/B075ZHDQFP (low cost $50 meter--good enough for our needs)
https://www.amazon.com/gp/product/B019CY4FB4 (medium priced $120 meter)

Note there are AC Current Clamp Meters--And they are perfectly good meters--But they do not measure DC current. Make sure you find an AC+DC current clamp meter (not AC current clamp + AC/DC voltmeter function).

Very easy to measure current--Zero the meter (DC clamp meters need zeroing). And clip on a single wire to measure current. For example, you can measure the current for each panel and ensure that they are all outputting the same current level.

-Bill

Warich

Update: Batteries sitting at rest charge of 12.7 volts over night with no charging.  All 4 batteries were disconnected, tested individually and unhooked from each other. with a 100 amp load tester for 10 seconds time on each battery. Each of them tested fine and stayed in the green range of being good according to battery chart for battery size and draw down load. Also purchased and performed a hydrometer test on each cell of all the batteries. Each were just above the 1.275 reading on all individual cells for each of the 4 batteries. 

In regards to switching out to an MPPT controller, it is my understanding that I need to rewire the 4 panels in a series vs the parallel to which they are now connected to the PWM controller. In doing so I should wire 2 panel sets of 12 volts in series to make 24 volts per set, then connect those 2 sets of 24 volts in parallel which is connected to the MPPT controller.  By doing this I create a higher voltage rating to the controller which reduces the amps, but keeps the voltage level in charging state. Is that correct?

I did an experiment this morning with the Eco-Worthy charge controller that I was currently using and a cheap chinese black and blue plastic controller that a friend gave me to try out. This was for the purpose of seeing if there was a possible issue with the one I have been using all along.

It's been very overcast and raining here for the last 48 hours. When I looked at my current PWM controller it was showing the PV panels were not sending any voltage input to the controller. I then changed out the controller and connected in the cheap chinese controller setting it to the correct parameter of float at 13.7 and FLA setting. Right away I noticed it had turned on the panels and was producing a charge to the batteries. The numbers changed from 12.7 to 12.8. After 20 minutes if flickered from 12.8 to 12.9.  I am unsure what the amperage range it was putting in, but was indeed doing something.  I then took that one out and put the original controller back in and it still didn't activate until 3 hours later when the sky was getting lighter out. So I am left with the thoughts of the controller being bad or that it just takes more light to activate? 

Since writing this morning, I have found a brand new in the box  Eepever 40 amp MPPT controller locally near my area. Does anyone know of these brands and if so are they any good?. It's a private sale they are asking $100.

mcgivor

Without the proper tool required, a clamp on ammeter in this case, it's difficult to really evaluate wether the controller is functional or not. The voltage reading on the controller will not be 100% accurate, the resolution of 100mA could actually be 12.751V or 12.849V on a 12.8V readout, not including a +/- 10% tollerance typical of lower end measuring devices.

There has been mixed reviews on the Epever controllers, no personal experience other than knowing people who are happy with them, they are quite sophisticated for the price,. My choice would be a more reputable make Morningstar, Midnight, Outback, Victron etcetera some of which offer a 5 year warranty and tech support , for a small system such as yours there will be little or no benifit using MPPT over PWM.

Warich

I understand the need for the clamp on ac/dc ammeter and have made the purchase of the one that was pointed out in an earlier post. Since my last post the original charge controller has failed about an hour later. For unknown reasons it quit showing voltage for incoming power and the LED screen flickered dimly. I sent off an email to the company to see if they will honor their warranty in getting it replaced. In the meantime I will be using the chinese PWM until a replacement arrives or I end up buying a better controller as recommended.