Voltage coming from panels is low?

I submitted a support ticket with Renogy but wanted to give the community an opportunity to weigh in as well.

This is the 3rd summer that I have had a solar system on my 5th wheel.  I leave my camper at the lake almost all summer and go out and camp on the weekends.  This means that during the week, the system is essentially just keeping the fridge running and the batteries topped off.  Very little draw.

I started with 200W worth of panels, but expanded to 400W last summer in preparation for installing an inverter.  All 4 panels are in parallel and are feeding into a Renogy Adventurer controller.  The system has been relatively trouble-free.

Two weekends ago, my wife and I got to our camper on a Friday afternoon.  Like I always do, I pulled out my phone to Bluetooth into the system and check how it's doing.  To my dismay, The batteries were only at 11.8V and no charging was going on.  I removed the access panel to the cubby where the controller is mounted and quickly found the problem.  The positive wire from the panel array came off of one side of the circuit breaker for the line.  I quickly made the repair and figured this would be no big deal.

I once again logged into the app to check on it.  The system was now working, but only just.  The app said panel array was only outputting 12.7V.  I didn't have a multimeter to verify this information.  We successfully camped through the weekend because we had no other alternative.  However, I was concerned because the system was unable to charge at 14.4V like the batteries require.

I ordered a new controller just in case, thinking for sure that the array couldn't actually be only putting out that voltage.  Once it was delivered, my wife and I made a special trip out to the lake just to install the controller.  When we got to the camper, I logged into the app and was surprised to find the panel voltage up around 19 or 20 volts.  This is what I always remembered.  The system appeared to be functioning normally so we elected NOT to replace the controller.

Fast forward to just this past weekend.  When we arrived at the camper, everything was fine.  Panel voltage was up around 20 again and the batteries were float charging at the correct voltage.  We again concluded that everything was fine and there was just a hiccup after I repaired the connection.  That night, we used the batteries quite a bit for our outdoor flood lights for activities.

In the morning, I checked the solar system and was disappointed to see that voltage was once again down in the 12-13 volt range.  This was at 9am with great sun exposure.  This time I did bring a multimeter and was able to confirm that the panel voltage reflected in the app is in fact correct.  The panels are only putting out the lower voltage.  Again, this prevented the controller from putting 14.4 volts into the batteries in "boost" mode.

Through the day, we watched the panel voltage climb and climb, all the way up to 20 volts again.


It was my wife that made the correlation that panel voltage seems to be depressed when we have used the batteries.  As the batteries start to "fill up" in the morning sun, the panel voltage goes up.


This completely flies in the face of my knowledge of how PV systems work.


In the time I've own the system, I seem the remember that panel voltage is always high in good sunlight, regardless of battery condition.


Is it possible I damaged my panels when the connection came loose?  The fact that all 4 panels are in parallel makes me think that is unlikely but who knows?



  • sounds normal to me. Panel voltage should = battery voltage in bulk charging, then you will see panel voltage rise in boost or absorption as the battery is held constant @14.4v. What is really happening is the panel is connecting and disconnecting to the battery to limit power, connected the panel operates @ batt voltage, disconnected it produces no power @ Voc of ~20v. in float it is main disconnected and you'll see 19-20v.

    It may take longer to charge these days since you let it sit in a discharged state.

  • In bulk it can't even make it to 14.4v most mornings.

    I can't be certain, but I'm pretty sure it didn't do this before.

  • it hadn't been discharged that low before and kept discharged for a period of time.

    You've shortened it life by not charging it ASAP.

  • "Period of time" in this context is 5 days.  Max.  The system was working fine on Sunday afternoon.  When we returned on Friday afternoon, the system was not functioning  I have no idea which day it disconnected.  I wouldn't think that keeping a propane fridge running for 5 days on a 200 Ah battery bank would cause permanent damage.

    But just so I am clear - you're saying that you believe the solar system is fine and my batteries have been irreparably damaged?

  • seems normal, each discharge does harm to batteries, they do not last forever, I am no saying to get rid of your batteries but keep plugging along till they don't supply your needs.

    check out battery sulfation and/or equalization,charged%20at%20lower%20charge%20currents.

  • @ 11.8v you are over 50% discharge, call it 75% or missing 150 ah, so if you put back 15ah/hr if takes time to get to say 80% charge when the batt would be 14.4v or so.

  • Alright, I understand.

    It seems unlikely that is occurring at night when I am using the LED outside lights.  I can't imagine how few amp-hours I am consuming.  So for it to be a repeat performance in the morning seems odd.

  • it is not odd to me that panel V matches battery V in the morning and that it takes time before the battery is at a set pt of 14.4v or whatever it may be. Then held constant for 2 hrs, then float or whatever your controller's charge profile. 

    the chemical reaction that produces power creates a sulfate on battery plates, the longer it sits there and the lower the battery voltage, the harder it is to reverse this lost capacity. That is what equalization is for, a purposeful over charge to attempt to fully reverse the chemical reaction making each cell equal with the others, used when needed ie specific gravity of electrolyte is different among cells.

    I have no other help for you 'cept to do some research about battery testing including hydrometer, about sulfation, about equalization, about battery aging, battery maintenance ... 

    Your battery's maker may be a good source!

Iniciar sesión o registrarse para publicar un comentario