Solar question

[davidludwig]

Hello,
I have a 2016 28’ Intl CCD with 1120w of solar on the roof.
4-Renogy 160w rigid panels and 3-160w Renogy flex panels. Inside I have a Victron MPPT 100/50 smart solar controller and a Victron BMV 712 multiplus inverter and 4-100ah new Lifepro lithium batteries.

With all this wattage on the roof, I never see more than 350w on the controller read out. I also have 100% set at 14.2a, but I consistently get reading of 100% with only 13.2w. Even after a day of full sun and a charge of “100%” I don’t have enough power to run my CPAP through the night without dropping below the 12v minimum and shutting off the inverter. This issue forces me to up-charge my batteries every night from 80% (after dinner and screen time uses) using my on-board Onan 2500 propane generator. What is preventing my batteries from getting a full charge?

[3OnOurWay]

So just fishing for ideas.

I have seen high solar voltage off of controller at 19/20v cause MPPt to cycle off, which then also reduces total wattage available into batteries.
Have you seen indicator of high voltage?
Somewhere here will help guide you for sure ..

[waninae39]

IMHO, get a second MMPT. I think the single MMPT is limiting the power in as you likely went over the voltage or current limit on the single unit

i have three MPPT in my As 2 FC 25fb with 560 W.
3 MPPT as i have 3 different types of panels.

it works well

[JeffKim]

Originally Posted by waninae39

IMHO, get a second MMPT. I think the single MMPT is limiting the power in as you likely went over the voltage or current limit on the single unit

i have three MPPT in my As 2 FC 25fb with 560 W.
3 MPPT as i have 3 different types of panels.

it works well

Back of the envelope if you have 1120W on the roof then that's 1120/12 = 93A peak and the controller will only output 50A.

Otherwise, how are the panels wired together? I haven't had the pleasure of wiring solar panels, so someone here might have a much more learned opinion, but I'm pretty sure you can't have an odd number of panels and wire them series/parallel or vice-versa without getting a reduced wattage. Basically you're combining arrays with different voltages and currents. I think the only thing that works is all parallel or all series.

If you have them in series any shading will drastically reduce the output. Also, that's about 7*22.9VOC = 160V which exceeds the input of the controller. If they are all parallel then that's 22.9VOC or so input with 7*8.37SSC=59A but then the wattage exceeds the output of the controller as stated.

[PaulBristol]

2016 28’ Intl CCD
1120w of solar on the roof.
4-Renogy 160w rigid panels
3-160w Renogy flex panels
Victron MPPT 100/50 smart solar controller
Victron BMV 712 shunt
multiplus inverter
4-100ah new Lifepro lithium batterie
I never see more than 350w on the controller read out.
100% set at 14.2a, but I consistently get reading of 100% with only 13.2w.


Issue #1
Even after a day of full sun and a charge of “100%” I don’t have enough power to run my CPAP through the night without dropping below the 12v minimum and shutting off the inverter.
charge my batteries every night from 80% using my on-board Onan 2500 propane generator. What is preventing my batteries from getting a full charge?


Solar system is poorly designed. You probably need a separate solar controller for each panel type. Check the specs for the two types. I think the open circuit voltage will be different for the two panel types. The Victron controller is high quality, but it can only maximize one input voltage


Any panels wired in series, only outputs what the minimum panel in the series outputs. Any panels in shade can limit any series connected output the the output of the shaded panel. Air conditioners, antennae, air vents can shade a panel. A curved roof can point one panel in one direction and another in another direction. Only one puts out maximum. The Victron can only maximize one panel.



50 amp controller maxes out at 600 watts. It should charge 400 amp hours of lithium batteries in 9 hours. You probably cannot harvest that much solar in one sunny summer day. Many people expect to harvest no more than 6 hours per day. Less in the morning. Less in the evening. Adds up to about 6 hours worth.


Get a second controller. One for each panel type. You may almost double your harvest.


Issue #2
400 amp hours of lithium batteries at 80% SoC is more than enough to run a CPAP all night. Something else is running and depleting your batteries. Look at the wattage on the CPAP power brick. I bet it is not that much.


It may help to shut of the humidifier. They draw significant power.

[waninae39]

Also,for each of panel types, do series and parallel connection. That helps to balance shade and uneven sunlight.

[kb0zke]

How the panels are wired together, as was mentioned above, is probably the issue. Wiring panels in series means that you add the VOC (open circuit voltage) and the amperage stays the same. Wiring panels in parallel means that the voltage stays the same and you add the amperage. Those panels are putting out approximately 13A and may have a VOC of ~20 vdc.


Adding another controller might be the easiest solution. Put the four panels into two parallel strings of two panels in series on one controller and put the three as one string in series on the other controller. Then you could parallel the two outputs to the MultiPlus II.



Check the actual VOC for your panels. Just to be safe I use the VOC when adding voltage and advertised watts divided by 12 volts to give me amps. That gives me the high end for voltage and amps. Since reality is actually somewhat less than those numbers I have a bit of a safety margin.

[tominphx]

This also may be due to the charge controller recognizing only 50 amps of the array's output and further loss due to exposure angle and/or possibly age degradation of the array. I could not find any 160W panels on the Renology website, they could be ageing out.

Cheers, Tom

[vanderwielen]

not enough information, but here's how'd I'd begin. Using your victron app, see what your solar panel voltages are. that will tell you if they are all parallel or a combination of parallel-series.

secondly, test each solar panel one at a time. with the battery state of charge below 80%, take a towel and throw it over each panel, under sunlight and observe that the total charge current decreases each time.

your array confuses me how it would be wired correctly and work within the parameters of your single MPPT... and I'm and E.E. (for all the facebook engineers, both the flex 160 and rigid 160 have nearly the same V.O.C, but using 7 panels does create an array that would work other than a series string which would exceed the MPPT input voltage. If he had 8 panels, I could see two series-parallel strings with a VOC of less than 100v.)

[tominphx]

vanderwielen, could you please explain the difference between Open Circuit Voltage (OCV) and Max Power Voltage (MPV)in relation to solar panel output.
I'm asking because I assumed that MPV was the max the panel could provide...
honestly I'd like to know because I guess, I'm one of those FBE's

Please don't take my reference to a FBE as jab at you.....serious question on my part!

Cheers, Tom

[vanderwielen]

Originally Posted by tominphx

vanderwielen, could you please explain the difference between Open Circuit Voltage (OCV) and Max Power Voltage (MPV)in relation to solar panel output.
I'm asking because I assumed that MPV was the max the panel could provide...
honestly I'd like to know because I guess, I'm one of those FBE's

Please don't take my reference to a FBE as jab at you.....serious question on my part!

Cheers, Tom

both are typically spec'd by the manfacturer, though MPV is more often called Vmp = Voltage at Maximum Power. OCV is simply the voltage you'd measure with a meter when the panel without any load. Vmp is the voltage, under load where the maximum power is produced. You'll also see Imp for max current at max power and Pmax as a measurement of power when both voltage and current are optimal. solar panel in parallel should be the same so all parameters are perfect and max power is achieved. Think of it as why we use the same size and manufacture of Lithium so the current from each is the same.

[tominphx]

vanderwielen, thank you, great explanation, always good to add to the knowledge base!

Cheers, Tom

[PaulBristol]

Power = Watts
Watts = Volts X AMPs
Open circuit watts = 30 volts X 0 amps = 0 watts
Short circuit watts = 0 volts X 30 amps = 0 watts
Approximate peak watts = 15 volts X 15 amps = 225 watts
Actually a lot more complicated than this, but this is good enough to plan a trip to Yellow Stone park.