Drop in Solar output after 4 years

[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?

[rsdata]

I suspect you have cleaned the panels before making these measurements?

Wire does not deteriorate so that part of the equation should not change, but what about corrosion on the terminals and those terminal connections?

I use the stuff below on all electrical connections to clean and prevent oxidation...

[TitanMike]

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?

I would check connections. Are panels connected in series as they should for the MPPT controller? Or are they wired in parallel. Regardless, loose or faulty connections can greatly reduce power output.

I pull 14 amp from two 100 watt panels at full sun wired in series. With three panels you should see just over 20 amps if wired in series. Output from solar panels should read around 50-55 volts.

I would isolate each panel and check individual outputs. Open Circuit Voltage in full sun should be ~22 volts (it's on the spec sticker on the back) for each panel.

Of course the obvious question has to be asked, "How clean are the panels?" An accumulation of dust and "pollution scum" can drastically reduce output. If sun can reach the silicon cells, power can't be produced.

[Sagecoachdriver]

Originally Posted by rsdata

I suspect you have cleaned the panels before making these measurements?

Wire does not deteriorate so that part of the equation should not change, but what about corrosion on the terminals and those terminal connections?

I use the stuff below on all electrical connections to clean and prevent oxidation...

Panels are clean and I did spray each connection with contact cleaner. I am replacing the connectors and the 30 amp fuses. Only thing left would be the cables.

[TitanMike]

Originally Posted by Sagecoachdriver

Panels are clean and I did spray each connection with contact cleaner. I am replacing the connectors and the 30 amp fuses. Only thing left would be the cables.

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.

[rsdata]

Only thing left would be the cables.

Wires don't fail... connections do...

I think the panel testing as TitanMike suggested would be the ticket... Panels do age and cells deteriorate...

[GravelRider]

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?

Are these rigid or flexible solar panels? The flexible ones are notorious for developing a bit of a glaze over them over time, thus decreasing output.

[Sagecoachdriver]

These are ridged panels. Good idea to check each panels output. I have new connectors arriving today and will check each panels output. Thanks

[sytsmasj]

Is the battery state of charge similar between the two readings?

[Sagecoachdriver]

Originally Posted by sytsmasj

Is the battery state of charge similar between the two readings?

The Renogy battery monitor is off as there is a parasitic drain of .2amps that is not reflected on the monitor. I have the batteries disconnected and have a 10-15 amp drain after a week or two. Not reflected on battery monitor still showing 100% and 200 amps. Voltage is the same or within .2 amps and voltage. on the controller and the battery monitor.
I received the new set of connectors and installed them. I found 2 connectors that needed replacing which I did. Do to overcast skies and late hour I was unable to see any real improvement or test each individual panel with voltage, amps and watts. Maybe tomorrow, heading out to the beach for 2 days.
I did order a 4 cable connector so I can add another panel if needed.

[TitanMike]

Originally Posted by Sagecoachdriver

The Renogy battery monitor is off as there is a parasitic drain of .2amps that is not reflected on the monitor. I have the batteries disconnected and have a 10-15 amp drain after a week or two. Not reflected on battery monitor still showing 100% and 200 amps. Voltage is the same or within .2 amps and voltage. on the controller and the battery monitor.
I received the new set of connectors and installed them. I found 2 connectors that needed replacing which I did. Do to overcast skies and late hour I was unable to see any real improvement or test each individual panel with voltage, amps and watts. Maybe tomorrow, heading out to the beach for 2 days.
I did order a 4 cable connector so I can add another panel if needed.

If you add another panel just like others it would be beneficial to connect them all in a series/parallel configuration. Connect pairs of two, in parallel, In series and utilize the MPPT controller to maximize efficiency. Earlier start of charging, later end of charging as sun goes down.

[Daniel.mullins4]

Solar panel output is much like a battery, the voltage output depends on the draw, that is the battery state of charge plus other items in RV drawing power, for me too difficult on a day to day basis while camping to compare the solar output readings. The short circuit voltage test on each panel would verify panel output.

[Sagecoachdriver]

Originally Posted by TitanMike

If you add another panel just like others it would be beneficial to connect them all in a series/parallel configuration. Connect pairs of two, in parallel, In series and utilize the MPPT controller to maximize efficiency. Earlier start of charging, later end of charging as sun goes down.

So you are saying rather than have them in parallel or all 3 or 4 going into one connector, have 2 go into one connector and the other 2 go into another connecter and then have the 2 cables go into another connector. Then do the same for the other cables. It's still in parallel right?

[Sagecoachdriver]

I originally used the branch connectors and they were dried out and one was missing the locking piece. I replaced them with the wire ones.

[kcmusa]

Last note, panels do deteriorate over time. Many have a spec sheet about how much output over how many years.

[TitanMike]

Originally Posted by kcmusa

Last note, panels do deteriorate over time. Many have a spec sheet about how much output over how many years.

Most panels built in the last few years have LONG warranties for power output.

[Sagecoachdriver]

Originally Posted by TitanMike

Most panels built in the last few years have LONG warranties for power output.

Yes,
25-year power output warranty: 5 year/95% efficiency rate, 10 year/90% efficiency rate, 25-year/80% efficiency rate.

At 4 years they should have lost maybe 5% not 30%+.

[TitanMike]

Originally Posted by Sagecoachdriver

So you are saying rather than have them in parallel or all 3 or 4 going into one connector, have 2 go into one connector and the other 2 go into another connecter and then have the 2 cables go into another connector. Then do the same for the other cables. It's still in parallel right?

Connect like this. Ignore voltages shown, your panels are more like 18-22 volts each and around 5 amp output. Just use the Diagram for cable connections.

[jbflag21ds]

And series-parallel let's you keep the smaller sized wire and fuse.

[Sagecoachdriver]

So the 24v 8 amps going into the controller brings itdown to 12v and how many amps? What would the controller be set at?