ROLAND CHUNG avatar image

Truck Camper - 160W solar panels had wires reversed. Working now, but only showing 23-35watts

Last week, I was able to get the solar controller to read the panel information and basically work. At first, I was happy to see about 75 to 80 watts. The camper is parked on the side of the house and is not using any electricity except for what may be lost by some electrical vampires (tv and entertainment system).

So, when I looked into the solar option for the camper, it turns out to be a 160 watt solar panel system. I'm only showing about 23-35 watts (31.59v / 0.7amps) everytime that I look at Victron Connect. When I look at the history, it shows 75 to 80 watts - being new to solar, I'm not exactly sure what I am looking at, but it seems like I'm not getting close to the 160 watts that I'm supposed to be getting.

My question - is it possible or likely that since the solar panels were connected to the controller with reversed wires since the production date (I pressume), the output of the panels might be compromised? I know that I have had the camper for over 3 months and it is likely that the camper was manufactured months before I got it.

I'm just asking the community as I would like to have some confidence if I need to have the manufacturer provide some warranty service to replace the solar panel.

Also, the manufacturer doesn't really have a reliable service partner in my area. Aside from removing the semiflexible panel from the curved area of the roof, I feel pretty comfortable swapping out the panel if necessary. I would just need to consult this forum for advice on removing the panel without damaging the aluminum roofing.

Please let me know what you think.



MPPT ControllersSolar Panelwiring
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solgato avatar image solgato commented ·

Something else to keep in mind is the relationship between your loads and what you’ll see when looking at the values in the App.

Others can correct t me if I’m wrong, but you should see almost full voltage output when conditions are ideal, but you may not see a lot of watts because your battery system and whatever loads you have connected aren’t needing much solar.

The watts have to have somewhere to go, so if your batteries are charged and your loads are not asking for much current, you’ll only see what watts are required to maintain your batttery bank and cover those loads and not the full watt output capability of your panels.

Turn something on and you should see the watt value rise along with amps to cover that load draw.

I think most people who are new to this stuff probably expect to see values that correspond with their system components when they use the App -that is to say they expect to see the max voltage rating, watt rating and the max amp rating their panels should put out when they launch the App, and when they don’t they assume something might be wrong.

I think this along with understanding that you want to feed MPPT’s with as much voltage as they can handle are the two most confusing things that may come up for first timers.

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Mark avatar image Mark ♦♦ solgato commented ·

Yes I agree, good point @Solgato!

So if you want to check for max solar power - do so when the charger is in 'bulk' phase OR alternatively turn on a significant load to bring down the battery voltage (from the setpoint target) & 'force' the MPPT to respond by increasing its output current.

Also, check that the MPPT charge current output limit (as set in Victron Connect app) is set to maximum & not limiting things (providing that your batteries can safely handle that charge current).

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2 Answers
Mark avatar image
Mark answered ·

I think that the solar power you are generating/seeing is very normal for an overcast day - when you typically only get somewhere between 5 to 20% of maximum output.

I don't know what the current conditions are like in your area, but have you had the chance to check the output during a nice clear day with very bright sun? (Then you should achieve somewhere around 60 to 80% max power output).

It is important to note that the solar panel max power rating can only be achived in ideal/perfect solar & temperature conditions (so if your getting above 80% max output it's a really good day).

Also, if the solar panel is shaded in any way (even partially) that will have a huge negative effect.

When you look at the history data in Victron Connect, you are probably looking at the daily maximum power that might have only been achieved momentarily or for a short duration. Then when you look at the live/instant data screen it would be normal for the power shown to be lower (compared to the maximum acheived over the entire day).

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ROLAND CHUNG avatar image
ROLAND CHUNG answered ·

Thanks Mark! I'm new to solar, so your perspective helps take the edge off of my concerns. I did see that 9 days ago, I had 80 watts max showing on my history, so there is quite a bit of variation.

So are you pretty certain that it is unlikely that I have any panel damage from the wires being reversed on the controller (MPPT 75/15) for months? I actually found the problem based on Christyler's suggestion that the wires might have been reversed by the factory. He suggested that reversing the wires would not have a harmful effect on the controller for a short period and I think that I've read that these Victron controllers are protected from reverse polarity, but it seems like being hooked up incorrectly for so long could have affected the panels.

I also know that the sun is still not directly overhead in CA and there is plenty of pollen landing on the trucks where I can see it - so I'm sure that it is landing on the solar panels. I will make time to clean the panels and keep track of what type of sun that we are having here.

Thanks again!

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Mark avatar image Mark ♦♦ commented ·

No problem Roland.

Yes I agree that 30w vs 80w is a significant variation, but it is very possible if the weather conditions or if shading between days is not comparable.

Also as you suggested, if some kind of obstruction (like leaves/branches or smaller particles) have permanently fallen onto your panel(s) & obstructing any individual solar cell then this would have a significant negative effect.

If the solar panel is mounted flat, rather than on an angle to be perpendicular to the sunlight, that also has a significant negative effect (worst in winter when the sun path is low, but also depending on the latitude of the area).

I can't be 100% sure that anything was damaged by having the solar panel polarity accidentally reversed for so long, but I would be more concerned about the MPPT rather than the panels.

The fact that it all 'seems' to be working now suggests that its all OK, but the real test would be to see what power you can generate during really good/ideal sunlight/solar conditions & with NO shading obstructions.

If you can generate a solar power output somewhere ~80% or more of the max rated power output (during ideal conditions) then I think that would prove for certain that everything is OK. But if its winter & 'gloomy' at the moment wherever you are, then you will probably have to wait for a better time of year to prove this out.

Do you just have the single 160w solar panel OR multiple?

If multiple what is the max power output of each individual solar panel & how are they wired (series or parallel or both)?

If you actually have multiple solar panels you could also test each panel individually to prove that each panel is 'contributing' to the combined power output.

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