Solar panel output too low?

[robertj]

I can’t give much advice other than an issue I had when one M4 connector broke down causing a huge drop in power delivered.
I cut off the connector and rejoined to get back to normal.

 

[lawrence_craig]

I have a cheap 100w semi-flexible panel from China and a Victron 75/15.

I only typically get about 20-25w at 14.5v in the middle of a clear sunny day.

I think maybe the cheap panels are rubbish.

Yep, mine are probably also from China and I have the same controller.

I am currently getting less than 50W from 300W in the Croatian midday sun.

I am looking to buy 'proper' ones in the winter.

Also, a note to the OP, these panels don't have proper waterproofing. Although they state IP67, they are not corrosion resistant which will eat away at your connectors depending on where they are mounted. I would also advise you get marine solar connectors. I got mine from the same supplier that I got my panels and although they look the same, they are a different material so also corrode.

 

[Roberto]

I had (have) the same problem, after changing three regulators and trying all,sorts of wiring I traced the fault in the panels, all 100W rated at 19v and 5.5A (ish), while measured one by one two gave only 3.7-3.8A and one 1.5A. Mind you, mine are 7-8year old, they were fine during their first days.
Winter project is sourcing something better quality to replace them.

 

[Alex_Blackwood]

https://www.thegreenage.co.uk/article/the-impact-of-temperature-on-solar-panels/

Worth reading. Forget that the article refers to domestic installations. All panels are effected by temperature.

 

[RichardS]

My 4 x 100W regularly produced a max power of around 250W when I first installed them 2 years ago, and even once reached a max of 350W when the boat and sun were aligned and there were no shadows at midday. However, the output gradually fell over the 2 years and are now totally dead and produce zero. I've check each panel separately off the boat with my multimeter and there is about 1 mV in high sun. They were installed slightly convex which is the preferred orientation.

All 4 panels have just been scrapped and I'll be starting again with different panels in 2 weeks time. :ambivalence:

Richard

 

[Mistroma]

Thank you for the numbers.
My panels do not droop, if anything they are convexing as the bimini is super tight. I also thought about that by reading about it online.
i have never seen decent output so as to believe that the panels where ok but somehow the performance dropped.

Sorry, I forgot to mention that my panels are now all rigid models. I bought 1x65W and 2x40W in 2012 and 2x100W in 2017. All from eBay and no performance problems so far apart from insufficient output at either end of the season (fact of life I'm afraid, I'd need 600W or more then ).

 

[Graham376]

I only had one semi-flexible panel which didn't last long. Rigid Chinese 320w (2 x 160w in parallel) output 300w+ on good clear days with charging voltages out of Victron 100/30 of 14.6v - 14.8v into Trojans, higher when equalising. Seems the OP's panels are not up to spec or, the controller needs to be on user defined settings rather than the standard ones in the menu.

 

[tsizkeik]

Ok so semi flex chinese panels are a poor investment, wish I knew that before i wasted 400 euros on them. Live and learn I guess. I will be posting test results next week, just in case some poor soul finds it helpful in the future. Thank you guys, downwinds and fair seas to all

 

[Bobc]

I've just been doing a bit of swatting-up on this, as I need to get some new panels and don't want to waste my money again.

It appears that there are a few things to look out for when buying semi-flexible panels:-

1./ Buy ETFE panels. They are a lot tougher and last longer. The dimpled surface also helps them reflect less light and hence absorb more, making them more efficient.

2./ Buy panels with "back connected" cells. The ones you see with silver lines all over them are front-connected. They are less robust and more prone to the electrical connectors cracking or corroding, and also produce less power. Back connected panels do not have silver bits showing over the black cells.

3./ Sunpower cells are the best, but there are different grades of cell ranging from "A" to "L". A is the lowest grade, and L is the highest grade. The L grade is about 24% efficient, whereas the A grade is only about 15% efficient.

So what you are looking for is an ETFE panel which uses Sunpower Maxgen III cells of a K or L grade, with back connections.

They are about, but they are about £250 for a 100w panel. So 3 times the price of the cheap Chinese ones, but produce 4 times the output and last 5 times as long, so actually better value.

Photonic Universe or Midsummer Energy are places to look in the UK.

Hope that helps.

 

[BrandoWilson]

I know that this problem occurred on old solar panel installations, but Now this technology has improved.

 

[BrandoWilson]

I got them installed by bates-electric.com and the power keeps a constant value between 90-120 watt of produced power. Keep in mind that the power is affected by more factors like weather, temperature, and the location where are you living. Is it worth it in the region where you're staying, to install a solar system or not? The panels still can collect solar energy during cloudy days, but the efficiency of the system drops as well the output power.

 

[Mistroma]

That's not a particularly useful link to a company in America on a forum not much frequented by Americans. Do you have any suitable UK companies to recommend? Photonic Universe or Midsummer Energy are often suggested for people UK. I've only bought via eBay so far and rigid panels still working well after many years cruising.

 

[forelle541]

Going right back to the second post the output voltage of the panels is low. Probably get what we pay for.

 

[ianj99]

The max stated output will be into a well discharged battery - probably well below 12v and will fall quickly as the battery voltage rises.