Solar performance

[geem]

Ours all manage 105% of rated output quite consistently. That's with Renogy ETFE panels, Victron controllers and lithium battery so you may get different results with pre-ETFE panels, poor controllers or bad batteries. It's not a flexi panel thing though, that's for certain. Rated output is rated output, end of story. Output per square metre might be worse than fixed panels but that's an entirely different conversation.

Will Prose did a video testing solar panels. He said he had never got rated output out of flexi panels ever. That is also my experience. Maybe you have the one good set of flexi panels ever made. You are the chosen one
I intend to buy 4x50w sunpower flexible panels when I get back to the UK since they seem to be the best I can find. I will see how we get on with those

 

[lustyd]

I like Will’s videos but that’s just nonsense. The rating on a panel isn’t some mythical number, it’s the power output of that panel in good conditions. If it couldn’t produce that they’d put a different number or make the panel slightly larger. Everyone I know gets over 100% in good conditions so I’d suggest installation problems are the issue.
If they were going to lie, they’d do it on fixed panels as well, surely?

 

[geem]

I like Will’s videos but that’s just nonsense. The rating on a panel isn’t some mythical number, it’s the power output of that panel in good conditions. If it couldn’t produce that they’d put a different number or make the panel slightly larger. Everyone I know gets over 100% in good conditions so I’d suggest installation problems are the issue.
If they were going to lie, they’d do it on fixed panels as well, surely?

So why does Will say he has never got the rated output in his tests? He is a well respected individual with a thriving Utube channel.
I have never go the rated output either. Many people have the same issue. My shitty Renogy panels are installed identically to my framed panels with the same controllers yet they perform very badly. They are in the same solar irradiance pointing the same direction. I have had similar bad experience with previous flexible panels. So why do the manufacturers lie about the output?

 

[noelex]

Ours all manage 105% of rated output quite consistently. That's with Renogy ETFE panels, Victron controllers and lithium battery so you may get different results with pre-ETFE panels, poor controllers or bad batteries. It's not a flexi panel thing though, that's for certain. Rated output is rated output, end of story. Output per square metre might be worse than fixed panels but that's an entirely different conversation.

In excellent solar conditions achieving the rated panel output (or higher), even briefly, is an important test that shows the solar panels and the rest of the system is working as it should be.

If you are measuring 105% from flexible panels I would be very happy . That is great recommendation for the Renogy ETFE panels. I have not personally seen any flexible panels that can do any better. I have seen rigid panels that in exceptional conditions can briefly deliver over 125%.

As you point out, all solar panels are measured in the same way under STC (standard test conditions). Therefore in these conditions panels of equal rating are performing the same. A 100w panel is a 100w panel.

However, there are some factors that mean in the real world that flexible panels do worse than rigid panels of the same rating. The first is temperature. STC are measured with a cell temperature of 25°C. In reality solar cells heat up rapidly under full sun. The STC test uses brief pulses of light as this is the only practical way to keep the cell temperature this low in full sun. Unless you live in a very cold climate it is likely the cell temperature will be higher than 25°C. 45°C is not uncommon. Even the best solar panels lose around 0.3% output for every degree rise in cell temperature. The colder they are the higher the output. Flexible panels heat up more than the glass and aluminium framed rigid panels, especially as it is more difficult to have airflow under the panel. This does not affect their rating under test conditions as the cell temperature is fixed, but hurts them in the real world.

The second factor is aging. Rigid panels age very slowly and even after 20 years are still capable of producing close to their rated output. Flexible panels age much more rapidly. Sometimes even the handling involved in shipping the panels to the retail store and then to the customer means micro cracks have developed and the panel is not delivering quite what it did on the test bench.

However, I do not think we should dismiss flexible panels. Many marine items have a life less than flexible solar panels. Even my expensive Aqua Signal LED tricolour/anchor light has failed after six years and it was programmed to do this by the manufacturer, but if you can fit rigid panels they will last longer and in the real world produce a higher output.

 

[Trident]

Will Prose did a video testing solar panels. He said he had never got rated output out of flexi panels ever. That is also my experience. Maybe you have the one good set of flexi panels ever made. You are the chosen one
I intend to buy 4x50w sunpower flexible panels when I get back to the UK since they seem to be the best I can find. I will see how we get on with those

My Renogy panels do the same - there is a big difference between the newer panels and older - I have 5 x 175w panels and all achieve full output despite being glued to a solid grp deck

 

[Trident]

I tend to just work by results and can't be bothered to note charge levels in and out and so on. We make hot water by electric every day for showers etc , we cook twice a day with electric, the other day made lunch followed by baking scones followed by baking bread, plus all sailing and boat loads, plus domestic full size fridge and freezer, 40 inch TV, Starlink, pcs etc

On days with full cloud we are full by 11 am and then make water , heat water, cook, etc and are full again by mid afternoon
On days with sun and cloud we are full by 9.30 and the same
On days with bright sun early we are full by 9 am and cannot possibly bake enough or make enough water or heat enough water to keep from wasting hours of sun by being in"float" mode.

We peak at just over 100A charge rate any time from 10.30 until 4 pm right now and 50-70 amp from about 9 am and after 4pm until about 6 pm - we still see 20amps in bright sun at 8pm even though all the panel are flat.

All are Renogy brand panels - a mix of flexible and solid. For reference we have 2100w
LifePo4 batteries - 700ah

My next project is to swap to 16 Eve cells for 560AH at 24V and swap from a Victron 12v 3000 inverter to a 24v 5000
This means my wife can happily run ever appliance on board at once when feeling creative in the kitchen and the 14kw battery bank will soak up all the power we waste now on good days so that hopefully we can run off grid all through winter (currently we need shore power from November to March) . If I can design the right thing for a bigger cockpit dodger I'll also add another 1000w of solar

 

[geem]

My Renogy panels do the same - there is a big difference between the newer panels and older - I have 5 x 175w panels and all achieve full output despite being glued to a solid grp deck

The Renogy panels I have are less than 18 months old and they have never performed well.

 

[Trident]

The Renogy panels I have are less than 18 months old and they have never performed well.

I'm pretty sure all the 50 w panels are older stock (edited for error)

Have you tried linking them in series for higher voltage ?

 

[B27]

There are some rubbish flexible panels about.
There are flexible panels being miss-sold on ebay and other places, the 'watt' rating is clearly not credible just looking at the physical area of PV cells.
Maybe they are talking about the watts of sunlight it can block or reflect rather than the electrical watts?
I bought a really cheap panel, supposedly 20W, allegedly Vpp 18volts or so.
In bright sunlight I couldn't get more than 400mA out of it short circuit, it gives about 22V open circuit.
It's trickle charging some old batteries for a water pump in the garden.
But literally so cheap not worth sending back.

If you suspect a panel is not its nominal power, it's perhaps worth checking its short circuit current in full sun, as that does not depend on the regulator or load. If you're measuring in a 'system' you should measure the volts as well as the current at the panel to have an idea that the panel is being loaded correctly.

 

[geem]

I'm pretty sure all the 50 amp panels are older stock

Have you tried linking them in series for higher voltage ?

They are 50w.
They are wired in series pairs. It doesn't matter if they are old stock. They are rated at 50w by Renogy but the performance is woeful. There is no way these panels will ever make 50w in normal use unlike framed panels that exceed the rating on a regular basis

 

[lustyd]

I went back and looked at Will P's channel and to say the least he is extremely biased towards his own use-case (arsing about with solar at his home) and hence he obviously prefers fixed panels. They are, after all, easier to mount in that situation and easier to move and store for his purposes. He's not done anything with flexi panels for 5+ years, and his video about them was mostly an Internet FUD fuelled rant by someone without qualifications (he's just a fan of solar, not a qualified electrician). As I said, I do like Will and he puts out some good content, but you do need to take it with a pinch of salt and know when he's giving bad advice and showing poor techniques.
I've posted my output on here before (Our first year with lithium) and demonstrated that flexible panels meet their ratings, it saddens me that some feel a need to continue to spread this misinformation. I get that some people have dud panels, fake panels etc. but that's entirely on them to rectify. If you can't get 100% out of ANY panel in good sunshine with a load able to accept it, then you either have a bad installation or you have a bad panel - return that bad panel, don't spread shit on the Internet about it.

 

[B27]

Geem, You should perhaps be having this conversation with Renogy rather than bad mouthing them on here?
How are they connected?
How are you measuring their output?
Are you measuring the best the panel can do, or the performance of a mis-matched system?

edited to make clear I was replying to Geem.

 

[geem]

Geem, You should perhaps be having this conversation with Renogy rather than bad mouthing them on here?
How are they connected?
How are you measuring their output?
Are you measuring the best the panel can do, or the performance of a mis-matched system?

edited to make clear I was replying to Geem.

I have been through this before on another thread. I am a qualified mechanical and electric engineer.
My framed panels and my Renogy flexible panels are both wired up identically. This allows me to make side by side comparisons. The framed panels are wired in series pairs to Victron MPPTs ditto for the Renogy flexi panels. All readings are taken from the Victron mppt data logging function. I have swapped Victron Mppts to check that wasn't the issue. They massively under perform compared to glass framed panels.
As has been suggested on this thread, some lose of performance can be expected as the flexi panels will get hotter than the glass panels as the flexis don't have air flow under them, but this doesn't explain the vast difference in performance.

 

[lustyd]

As has been suggested on this thread, some lose of performance can be expected as the flexi panels will get hotter than the glass panels as the flexis don't have air flow under them, but this doesn't explain the vast difference in performance.

And as I showed in the other thread that’s just not the case. If you have an issue take it up with Renogy, it’s NOT a flex panel issue.

 

[geem]

I went back and looked at Will P's channel and to say the least he is extremely biased towards his own use-case (arsing about with solar at his home) and hence he obviously prefers fixed panels. They are, after all, easier to mount in that situation and easier to move and store for his purposes. He's not done anything with flexi panels for 5+ years, and his video about them was mostly an Internet FUD fuelled rant by someone without qualifications (he's just a fan of solar, not a qualified electrician). As I said, I do like Will and he puts out some good content, but you do need to take it with a pinch of salt and know when he's giving bad advice and showing poor techniques.
I've posted my output on here before (Our first year with lithium) and demonstrated that flexible panels meet their ratings, it saddens me that some feel a need to continue to spread this misinformation. I get that some people have dud panels, fake panels etc. but that's entirely on them to rectify. If you can't get 100% out of ANY panel in good sunshine with a load able to accept it, then you either have a bad installation or you have a bad panel - return that bad panel, don't spread shit on the Internet about it.

Have a look at this test from 3 years ago

It a very fair test. Even with a flexi mounted in free air. Not fixed to a deck or bimini it still doesn't perform to spec

 

[lustyd]

edited- watching on phone in sun

 

[lustyd]

Ok so he seems to get poor output from some rigid panels, slightly under on one flex panel and shows absolutely no due diligence in speaking to the suppliers about the issue. Thoroughly unprofessional and inconclusive in my opinion.

 

[geem]

Ok so he seems to get poor output from some rigid panels, slightly under on one flex panel and shows absolutely no due diligence in speaking to the suppliers about the issue. Thoroughly unprofessional and inconclusive in my opinion.

He's utuber not Oxford University!

 

[lustyd]

He's utuber not Oxford University!

Exactly what I’m saying. He’s an amateur badmouthing products in a public forum without doing any due diligence to back up his claims. Not far off your story, just a larger audience.
Anecdotes aren’t facts, and without speaking to the manufacturer to determine where the problem lies it’s probably better to stay quiet on the matter.

 

[geem]

Exactly what I’m saying. He’s an amateur badmouthing products in a public forum without doing any due diligence to back up his claims. Not far off your story, just a larger audience.
Anecdotes aren’t facts, and without speaking to the manufacturer to determine where the problem lies it’s probably better to stay quiet on the matter.

No. That would be no fun.
I have four identical panels. They all make the same amps when tested individually. They all have the same open circuit voltage when tested individually. There is not a bad panel. They are all bad and do not make their rated output, ever. What do you think Renogy will say? We will give 4 new panels? We will give you your money back? That isn't going to happen. If I can let other know not to buy these particular flexi panels then at least nobody else with be disappointed. Will Prowse has the same opinion as me based on his experience. I know yours is not the same and I am happy for you.