I only get 85W out of my Two Renogy 100W panels

[Serge9898]

I have two "100 Watt 12 Volt Flexible Monocrystalline Solar Panels" (SKU: RNG-100DB-H-US) in parallel, on my camper van, on a "Renogy Adventurer 30A Solar Charge Controller and Battery Monitor flush mount controller and a Renogy Battery Monitor" and a "Renogy Battery Monitor 500W" (SKU: RBM500-US)

On a bright sunny day I get 43W and 45W from each panel, for a total of 88W. (In March in San Jose California).
In Summer I may get up to 120W total. (But never close to the expected 200W?

What output power should I get from these 2 solar panel? I would expect at least 150-185W in full sun in summer...
How to troubleshoot and solve this issue and get closer to the expected 200W?
Thanks for your help!

 

[MisterSandals]

In March in California

Laying flat on a vehicle at the Oregon border a LOT different than at the Mexico boarder. So without a location i'm thinking thats pretty typical for thin panels.

I pulled a new 200W thin panel off my RV the day i brought it home.

 

[sumpower]

The PWM charge controller is a limiting factor for panel efficiency to play out well. Also having panels lay flat on the roof of your vehicle make the panels a heat sink, thus making them less efficient.

 

[Whinny]

The connector just to the right of centre looks like it may be shading some of the panel. Any shade there will impact performance.

 

[740GLE]

The connector just to the right of centre looks like it may be shading some of the panel. Any shade there will impact performance.

Not to mention the shrubbery or the overcast cloudy day the pictures were taken.

 

[hybe022]

I have two "100 Watt 12 Volt Flexible Monocrystalline Solar Panels" (SKU: RNG-100DB-H-US) in parallel, on my camper van, on a "Renogy Adventurer 30A Solar Charge Controller and Battery Monitor flush mount controller and a Renogy Battery Monitor" and a "Renogy Battery Monitor 500W" (SKU: RBM500-US)

On a bright sunny day I get 43W and 45W from each panel, for a total of 88W. (In March in San Jose California).
In Summer I may get up to 120W total. (But never close to the expected 200W?

What output power should I get from these 2 solar panel? I would expect at least 150-185W in full sun in summer...
How to troubleshoot and solve this issue and get closer to the expected 200W?
Thanks for your help!

get an mppt. that renogy uses pwm which has lower efficiency.

irradiance, tilt angle, etc. there's just a lot of factors to consider.
not to mention other losses from wires.

 

[Q-Dog]

How old are those panels? The flexible panels aren't exactly known for their longevity.

 

[Serge9898]

Not to mention the shrubbery or the overcast cloudy day the pictures were taken.

Yes you are very observant. The picture was taken on an cloudy day. But as I mentionned the measure made on a bright sunny day .
The connector on the right is not on the panel, it's parallax (and would represent less than 1% of the surface...)

 

[Serge9898]

How old are those panels? The flexible panels aren't exactly known for their longevity.

How old are those panels? The flexible panels aren't exactly known for their longevity.

One panel was replaced about a year ago. The other one is from 2019. As I also read about Renogy flexible longevity reputation and I was expecting to see a difference. I was very surprised (and pleased) to see no significant difference after 5 years!. So no longevity issue here. (May be because they are covered most the time).

FROM YOUR EXPERIENCE : How many watts do you get from your flexible panels (compare to nominal)?
Please specify the region (assuming the measure is made on a bright sunny day!)

 

[SouthernSolar]

The lose from improper tilt can be calculated cos(suns angle - actual tilt of panels )

In winter the difference could be as much as 60 degree or more with panels flat

Cos of 60 is .5 or a 50 percent loss.

 

[Serge9898]

The lose from improper tilt can be calculated cos(suns angle - actual tilt of panels )

In winter the difference could be as much as 60 degree or more with panels flat

Cos of 60 is .5 or a 50 percent loss.

@SouthernSolar thank you so much. That's really helpful! I learn a lot today!

A bit more details after my research (for other beginners like me):

I am near San Francisco, (40°N latitude) where the sun reaches its highest point at around 72 degrees above the horizon at noon during the summer solstice (around June 21st), and only about 28 degrees above the horizon at noon during the winter solstice (around December 21st). Say it's 30 degree above the horizon now.

Sin 30 degree = 0.5. So my 100W panel flat on my roof can provide a max of 50W in winter (50%). And Sin 72 deg = 0.9, so it provides a max of 90W at the end of June!
Do you have a source about this sin approximation (Or cos from vertical angle) for the panel efficiency? I couldn't find.

 

[FishHog]

I get about 50% of rated capacity on my flat van roof mounted panels. Slightly more when sun is at its peak but I wouldn’t expect much better. Mine aren’t even flexible panels

 

[mikefitz]

On a bright sunny day I get 43W and 45W from each panel, for a total of 88W

With a PWM controller only panel amps are transfered by the controller. Typical maximum 100 watt panel current is 5 amps, 10 amps for two in parallel. With a charging voltage of 14 volts, that's a maximum of 140 watts.
Because your panels are not aligned you will lose a parentage of this 5 amp current, ( panel current is predominately effected by amount of solar irradiance).
To improve things, a) change to a MPPT controller, b) tilt panels to optimum angle.
Of course b) Is not practical on a camper if you want solar power in winter. Adding additional ground mount portable panels is an option.

 

[Sweet Tatorman]

When doing a quick evaluation of panels, I prefer to measure Isc as it is the parameter least effected by temperature. Orient the panel so that the sun rays are normal to the panel on a clear day and measure either by running the panel output thru an ammeter or short the output cables and measure with a DC clamp meter if you have one. I have no experience with renogy but in my experience the low-end panels can be pretty bad relative to spec. I have measured as low a 40% on a single panel and as low as 54% average in a set on 4 identical panels.

 

[SouthernSolar]

@SouthernSolar thank you so much. That's really helpful! I learn a lot today!

A bit more details after my research (for other beginners like me):

I am near San Francisco, (40°N latitude) where the sun reaches its highest point at around 72 degrees above the horizon at noon during the summer solstice (around June 21st), and only about 28 degrees above the horizon at noon during the winter solstice (around December 21st). Say it's 30 degree about the horizon now.

Sin 30 degree = 0.5. So my 100W panel flat on my roof can provide a max of 50W in winter (50%). And Sin 72 deg = 0.9, so it provides a max of 90W at the end of June!
Do you have a source about this sin approximation (Or cos from vertical angle) for the panel efficiency? I couldn't find.
View attachment 284384View attachment 284386

I don't have the white paper where I got the information from. I remember that when I found it it was pretty simple idea and remembered it. I am not sure why it's not referenced more often.

i had it bookmarked on my work computer and then retired.

 

[SouthernSolar]

Here an article on it, but it's complicated. The white paper I read explained it where it was easy to understand.

You may find more by searching " cosine effect solar"

https://www.atlantis-press.com/article/25868132.pdf

 

[Serge9898]

I don't have the white paper where I got the information from. I remember that when I found it it was pretty simple idea and remembered it. I am not sure why it's not referenced more often.

i had it bookmarked on my work computer and then retired.

" I am not sure why it's not referenced more often. i had it bookmarked on my work computer and then retired." I love it!
The simple (Cos α) seems pretty intuitive... And you made my day when I was able to show my daughter in high school that trigonometry was actually "useful in real life"!

 

[Serge9898]

With a PWM controller only panel amps are transfered by the controller. Typical maximum 100 watt panel current is 5 amps, 10 amps for two in parallel. With a charging voltage of 14 volts, that's a maximum of 140 watts.
Because your panels are not aligned you will lose a parentage of this 5 amp current, ( panel current is predominately effected by amount of solar irradiance).
To improve things, a) change to a MPPT controller, b) tilt panels to optimum angle.
Of course b) Is not practical on a camper if you want solar power in winter. Adding additional ground mount portable panels is an option.
View attachment 284414

Ok thank you! (Thanks for the MPPT recommendation. I guess it's more modification project I can handle now! Good learning though)
I am considering to get an additional ground foldable 100w 12v panel. I guess I need to plug it in parallel on my Renogy Adventurer 30A Solar Charge Controller. I found this Predator 100W at $129 at HF, is it any good?
I need to do some research on how to connect it to my in a simple way with a plug. Any direction to make it easy to plug?