Our first year with lithium

[lustyd]

I will check the surface temperature of the panels later and compare and report back

My ETFE ones are usually way too hot to touch and still output 104% rated output. Did you test them when new against the numbers on the back label? It's possible you have some damaged panels and didn't realise it.
Efficiency rating doesn't change the output, it changes the size of the panel. lower efficiency means bigger panels for a given rating, but they should give the rated output in reasonable unshaded conditions so if you have 200W of any panel you should get 200W output. Obviously if you don't connect sufficient load, or use the wrong controller results will vary, but with enough load and a suitable controller you should always get 100% rated output in sunshine.

 

[geem]

My ETFE ones are usually way too hot to touch and still output 104% rated output. Did you test them when new against the numbers on the back label? It's possible you have some damaged panels and didn't realise it.
Efficiency rating doesn't change the output, it changes the size of the panel. lower efficiency means bigger panels for a given rating, but they should give the rated output in reasonable unshaded conditions so if you have 200W of any panel you should get 200W output. Obviously if you don't connect sufficient load, or use the wrong controller results will vary, but with enough load and a suitable controller you should always get 100% rated output in sunshine.

I have never had any succes with flexible panels. The panels are wired to a dedicated Victron MPPT.

 

[lustyd]

The panels are wired in series pairs thethen

The configuration is irrelevant in good conditions since the rated output is in Watts. Configuration will change the voltage and amperage on the output leads but watts will remain the same.

 

[geem]

The configuration is irrelevant in good conditions since the rated output is in Watts. Configuration will change the voltage and amperage on the output leads but watts will remain the same.

Yes, I know. The fact that they are wired as 24v vastly reduces volt drop as well so its not an issue of connecting cables. They just don't meet their specified output. I won't be buying Renogy again

 

[lustyd]

It's definitely not a Renogy issue, they are in widespread use and work as advertised.

Being 24V battery might actually work against you in terms of yield as you'd only need to lose one side of a panel to shading and you're below threshold voltage whereas with 12V you'd have a lot more headroom in the MPPT input compared to output. If you lose one string of cells on one panel you'd be at 27.75V which is fine for a 12V system but not a 24V system. The parallel might save you there of course, but it's less certain.

 

[geem]

It's definitely not a Renogy issue, they are in widespread use and work as advertised.

Being 24V battery might actually work against you in terms of yield as you'd only need to lose one side of a panel to shading and you're below threshold voltage whereas with 12V you'd have a lot more headroom in the MPPT input compared to output. If you lose one string of cells on one panel you'd be at 27.75V which is fine for a 12V system but not a 24V system. The parallel might save you there of course, but it's less certain.

They are not shaded. We are monitoring peak output via the mppt. Shading during part of the day would only impact the daily yield. Peak output is the instantaneous maximum that the panels can produce in Watts. The panels are angled towards the sun. They simply do not provide the output they say they should. I can disconnect half the panels and run on 100w and still get very poor peak performance. I might do that later when the sun is high and do a comparison on the series pair's. That will show up and differences.

 

[Trident]

@Trident, are you based somewhere that sun shines, if not, no offence, I would not buy something based on your experience...
When I started rebuilding my boat, ppl recommended v.highly Owtrol (?) for treating iroko. Promptly bought a 4-5lt can and still have more than half of it as it only lasted a few months down here - not even a full May to Oct.
Even for the two framed 300W 1X2m panels I have on the hardtop I can see a drop in performance after 5-6yrs

I have fitted these to boats that are in Caribbean, the Med, and all points in between - my own boat has been UK, southern France and Spain and Netherlands and two UK years had 40 degree summers but certainly not full time in the tropics yet. It's where we're headed now so I'll update in a couple of years but Renogy sell all over the world and since they changed to the newer panels about 3 years ago I have heard no complaints at all .

It will depend when your framed panels were made too - the technology has changed quite a bit in the last few years - but IIRC most figures and warranties are based on 25C temperatures on average and they expect full performance for 10 years and serviceable 80% performance at 20 or 25.

 

[GHA]

Can't remember what make my panels are.
But they're better than everyone else's

Wind gens are a rare sight (and sound ) these days in cruising anchorages. Times change.

 

[geem]

I just put my temperature probe on my Renogy panels that are mounted on a canvas backing and then on the sun cover. Surface temperature is 44degC. The framed panels mounted on the guardwires have a surface temperature of 37degC. Some difference but not enough to explain the poor performance of the Renogy flexible panels
Edit
I waited until both pairs of panels were in full sun. Both pairs of panels have the same angle. With both pairs connected, we get 3.2A@24v with one disconnected, we see 1.6A so both pairs of panels are performing the same. It's not an installation issue. The panels simply do not meet Renogys own claims.
This is not the first time we have experienced this with flexible panels.

 

[lustyd]

They should be at 37V for a pair in series, and MPPT output ought to be somewhere around 28V, where are you measuring that?

 

[geem]

They should be at 37V for a pair in series, and MPPT output ought to be somewhere around 28V, where are you measuring that?

Two pairs in series then paralleled on to a single MPPT

 

[lustyd]

You’re down at 80W now are you sure you fitted them to the roof and not the keel voltage does look right but think I’d want to test the panels one by one. If I was consistently getting those results I’d want a refund or replacement, although realise that may be harder than it is here.

 

[geem]

You’re down at 80W now are you sure you fitted them to the roof and not the keel voltage does look right but think I’d want to test the panels one by one. If I was consistently getting those results I’d want a refund or replacement, although realise that may be harder than it is here.

I just checked surface temperatures on all four panels. One is at 46degC. The lowest at 40degC. Something odd going on. All mounted the same and all in sun

 

[lustyd]

For reference, here are my Renogy 2x100W flexible ETFE panels (Amazon.co.uk) taken on a very hot day in 2021. They still output this much when clean and in the sunshine. It's not a Renogy problem and it's not a flexi panel problem, but I will agree that you have a problem with your Renogy flexi panels.

 

[geem]

For reference, here are my Renogy 2x100W flexible ETFE panels (Amazon.co.uk) taken on a very hot day in 2021. They still output this much when clean and in the sunshine. It's not a Renogy problem and it's not a flexi panel problem, but I will agree that you have a problem with your Renogy flexi panels.
View attachment 175986

Here is them mounted for the avoidance of doubt

 

[lustyd]

I like the canvas setup, may make one of those for myself for when we're anchored it would double our input for not much space. There's certainly nothing obvious wrong, but you're definitely not getting what you should out of them

 

[geem]

I like the canvas setup, may make one of those for myself for when we're anchored it would double our input for not much space. There's certainly nothing obvious wrong, but you're definitely not getting what you should out of them

Yep, frustrating.
The set up works well. even with the poor output, we get enough to run our watermaker every day when at anchor.
It's difficult to sort out any issue with Renogy in the USA. We bought them in the USA and had them shipped to Antigua. Renogy USA are notoriously very poor with after sales service. The general advice on all the forums in the US is not to buy anything from Renogy for this reason

 

[Sea Change]

Can't remember what make my panels are.
But they're better than everyone else's

Wind gens are a rare sight (and sound ) these days in cruising anchorages. Times change.

And one day generators will also be a rare sound. I can't wait.

 

[GHA]

And one day generators will also be a rare sound. I can't wait.

They are on my boat already Though the little Honda gets a run now & then just to make it feel needed

See water coming out of an exhaust for a while now in the anchorage, it's "well you ain't got no Lithium mate, have you"

 

[Neeves]

Here is them mounted for the avoidance of doubtView attachment 175987

Ignoring your issues

Solar blankets are commonplace, you can buy them 'off the shelf' here, primarily for the 4x4 market as they have the same issues, space for solar panels, as do yachts. I have no experience with them but Grifth (spelling?) bought one, I think about 6-12 months ago, for his trailer sailor.

I have this fear that the panels might be 'bottom end' of the market (and they might be flexible or fixed - I have never checked).

But you do illustrate why one might need multiple MPPTs - different types of panel, different location, different age of panel and variable shade.

A passing thought: I believe panels are made specifically to fit in the 'valley' in domestic steel roofing (the valley, or dyke, seems to be to a standard size). They are long and skinny. They might be good, with support, attached to toe rails, stanchions or boom covers (though they would be really difficult to store if you wanted to remove them when at sea). This 'sort of thing' New 50 Watt 12v Monocrystalline Solar Panel - Free Freight* 50w 1220x290 | eBay. They seem to be an American thing,

Size​

Solar shingles are about the same size as traditional roofing shingles, with the average size being about 12 inches wide by 86 inches long, and weighing about 13 pounds per square foot. The thin tiles are less than an inch in thickness. It takes about 350 tiles to complete a typical solar roof installation.

Jonathan