Drop in Solar output after 4 years

[pcsdpo]

You can't expect the reach the "rated" output of solar panels when they are not facing the sun directly. If you want to get some fancy calculations, there is this solar calculation website:
https://pvwatts.nrel.gov/pvwatts.php
From NREL - Dept. of Energy Laboratory. You can enter most anything that will affect your solar collection abilities and see how it affects your charging. You first put in your location (zip code is easy if you know it), angle of your panels from flat to vertical . . . and a lot of other variables to calculate your efficiency. I think the greatest loss will be the angle of the panels to the sun.

Also a thought, there are different stages of battery charging as reported by your monitor and these different stages supply different voltages and amperages to properly charge your batteries. So, you are probably displaying the volts and amps being sent to the battery to charge it rather than solar power input to the controller. The bulk charge is your highest voltage*amps when the battery is usually below 80% capacity. Then absorption charge above 80% of capacity up until 94% and the voltage*amperage is "less" than the previous stage. The last charge level is "float" or "trickle" charge when the battery is above 95% but below 100%. Other chargers/controllers have additional stages.

And as mentioned before, if you put your panels in series, they will combine to deliver electricity at the voltage additive of the individual panels voltage output. This will then allow you to use a smaller wire from the panels to the controller. If you purchase a 4th panel then you can connect one set of 2 panels in series and the other set of 2 in series. Each "series set" produces the same output of double the voltage of the individual panels (usually about 22v + 22v =~ 44v). Then you connect the two "series sets" of panels in parallel as shown on that diagram.

You should also verify how much voltage input your MPPT controller will accept. Mine will accept 100 volts (usually 4 panels at about 22 volts apiece in series). MPPT controllers also have more intelligence than a PWM controller so their output will vary depending upon the solar input and charging stage needs.

[frankraney]

Originally Posted by TitanMike

Save yourself some time and check output from each panel. Panel output can impacted if there is a bypass diode failure. Start with the source (panels) and make sure you have proper output before chasing wire or connector problems.

Panel will only degrade about 1% a year....so. you are on track.... Some diodes are bad.....I lost quite a few on my house and my output went way down.

[DavidWJ]

Solar panels don't last all that long. Ten years is not bad for inexpensive panels. I wouldn't think there would be failure within 4 years, but it's possible.



Check each panel for output, then make sure the connections are clean.


Some China solar wiring is Aluminum and it can degrade, especially when exposed to heat. Might be worth checking the resistance on your wiring.

[frankraney]

Originally Posted by Sagecoachdriver

I installed 3 100 watt Renogy solar panels and their 30 amp MTTP controller. I was getting around 14 amps to my BB lithium batteries. Now I am getting only 10-11 amps. I am taking a reading at noon on clear sunny days. My first check was on the summer solstace. The volts from the panels shows 19.7v output on the controller disconnected from the batteries and only 16.5v when connected. Also the Renogy battery monitor shows only 145-147 watts coming from the 300 watt panels. My panel cables are joined with connectors and the 2 cables are routed to the fridge vent, down the side of the fridge and under the cabinets to the raise area at trhe rear of the MH. From there it continues under the floor across the the passenger side and forward to the controller. It's 25 feet and another 30" to the batteries. The cable is 10 awg as 8 awg was too stiff for fishing thru. I would expect some line voltage loss but not that much. Any thoughts?

Sounds like you have them connected in parallel. This gives you 24.3 volts open circuit, and 20.3 volts loaded @ 14.79 amps. Add the battery chargers the current will go down...... This sounds like what you had at first, so the battery was probably low?

Your panels are 100 watt each at 4.93 amps loaded and 20.3 volts. Connected to a load (battery) this will change as the battery gets full, untill they equalize. Then the current will go to almost zero, and the volts will match. So....... Looks like you're are ok. Turn off the solar, let the battery drain, then turn on the solar. Does it look like what you started with?

Your half power(watts) tells me it is working. Your 300 watts is maximum. As the batteries charge your current goes down, the panel resistance does not change, so the watts drop. Power = amps x volts. So as you can see, as either the voltage or current goes down so does the power.

[dlambers]

What you could be seeing is the result of a deteriorating connection. Start at the batteries and check/clean each one.

[doanshop]

Any shade will effect output
wired in series shade will effect all panels
wired in parallel shade will only effect the one panel
shade from a/c will effect it
angle of sun will effect out put

[Tommyh]

Hope this isn't a dumb question but did you make sure your MPPT controller was set to charge the type of batteries you have?

[DogFather]

If the system performance meets your needs, it might be time to let go with trying to fix a condition that ain't broke. Otherwise, as has been suggested, just refresh the connections and, if necessary, throw another panel up there - and move on with enjoying life.

[Sagecoachdriver]

Originally Posted by Tommyh

Hope this isn't a dumb question but did you make sure your MPPT controller was set to charge the type of batteries you have?

Yes, many times

[Sagecoachdriver]

Actually, the 300 watts has been doing the job even with the low output. I tend to use about 50-70 ah over night and it appears to fully charge or at least get to 90%+ every day so far in full sun sites. Except of course in Yosemite with all the trees. Then the solar is just enough to continue providing for the fridge and fans but with little added to the battery bank. Have to run the generator for 90 minutes to fully charge the bank of 2-100 amp Lithiums. Better than the 4.5-6 hours with lead acid.

[GravelRider]

Originally Posted by Sagecoachdriver

so the sun came thru for a bit. Placed Renogy solar 100 watt suitcase panel flat on ground. first photo 3 roof top panels. Second Renogy 100w suitcase and third is combined. Remember, it's not full sun producing maximum output. Hazy and almost overcast.

Can you plug your solar suitcase into the wiring you have on the roof? If it then reads similar readings to the roof panels, than you know it's not the panels. If its output his higher, it's the panels themselves.

[Sagecoachdriver]

Originally Posted by GravelRider

Can you plug your solar suitcase into the wiring you have on the roof? If it then reads similar readings to the roof panels, than you know it's not the panels. If its output his higher, it's the panels themselves.

There are photos here of the battery monitor reflecting the 3 panels, just the suitcase and combined. Ther suitcase output is 1amp more than each roof top panel produces. Suitcase was laid flat on ground.
Can't do any testing that requires my going on the roof. DW doesn't want me up there. Will have to wait until she's not around. Also, weather here in LA has been cooler with in the 80's with haze and cloud cover. Panels aren't putting out their max.

[jaudet71]

I have the same Renogy monitor and it just shows the amount the of charge going to the batteries. Just what is left after subtracting the draw on the batteries (fridge, detectors, boosters etc.)
I look at my controller to see what the panels are actually putting out if my batteries are somewhat down. If my batteries are well charged then it only shows what they need.
My monitor always shows less than my controller due to some usage. At least with the shunt hooked up as directed by the Renogy. If my batteries don't need it..... the amount shown in either the monitor or controller would be less.

What I am saying is that even with the same sun it is always different based on need.


I have only 10 AWG with 960W of panels wired in series and parallel for 50 to 60V. Mounted flat I can get 50 Amp output even in Maine as the pic below shows.

[Sagecoachdriver]

Originally Posted by jaudet71

I have the same Renogy monitor and it just shows the amount the of charge going to the batteries. Just what is left after subtracting the draw on the batteries (fridge, detectors, boosters etc.)
I look at my controller to see what the panels are actually putting out if my batteries are somewhat down. If my batteries are well charged then it only shows what they need.
My monitor always shows less than my controller due to some usage. At least with the shunt hooked up as directed by the Renogy. If my batteries don't need it..... the amount shown in either the monitor or controller would be less.

What I am saying is that even with the same sun it is always different based on need.


I have only 10 AWG with 960W of panels wired in series and parallel for 50 to 60V. Mounted flat I can get 50 Amp output even in Maine as the pic below shows.

I think I understand what you are saying. But I have all my cables going to a buss bar and a single cable going to a Bussman resettable fuse and to the battery. I use the resettable fuse as my cut-off isolator. When the resettable fuse is open, there shouldn't be any draw off the batteries. But there is about .4 amps parasitic drain continually drawn off. Maybe from the controller and battery monitor. So that only adds .4amps of load. that's no where near what I think it should be.

[jaudet71]

Being isolated is good to test then. Just have the batteries down enough to require bulk charge.


I was making 747W out of 960W claimed which is 77.8%. On one test you were getting 166W out of 300W which is 55.3%. Using higher voltage is more efficient but that probably accounts for just some of the deficiency that you are experiencing. Like I said I only have 10 AWG and make my own connections. I think your 10AWG is plenty good. I have 3 170AH Renogy batteries that will accept a large amount of amps at once. A smaller bank might also be another factor. It all adds up.



Maybe a connection, fuse or somewhere is not at 100% of what it should be.
By specs my Renogy panels wired in series (2 sets of 3 each) then the 2 sets in parallel should produce up to 60V and 16A for 960W. My Renogy 60A controller changes that to 12V at whatever amps are available for the battery. Really the only important setting is for lithium.

I guess I am fortunate that it works as well as it does considering I rarely clean my panels except when I wash the whole RV.


Good luck on figuring it out!!!

[jaudet71]

Back when I had only 340AH of batteries and 640W of panels this pic shows I was getting 472W out of 640W of panels for 73.75%. Again that was in Maine at about the 44th parallel. Two sets of 2 in series and the two sets in parallel.