Stung with <span class="highlight">solar</span>

Are they mounted on anything and what sort of controller are you using?
Keith

Unless you have a solar radiation meter, you have no idea what the solar insolation is, and consequently cannot get an accurate reading on the solar output. There can be what looks a perfectly clear sky, and in fact it is far from what it looks. Yes, I have a solar radiation meter. The solar panel would also have to be angled at the correct angle to the sun on a flat surface. Flexible panels will generally have a reduced output due to not being able to cool sufficiently/quickly.
Easy to calculate the effective wattage output from the area of the solar panel.
Flexible solar panels have an incredibly high failure rate, reason the short warranty.

qldcamper
Any panel. flexible or otherwise fixed panel with no reference to current is going to be far less than claimed. 100W in perfect conditions maybe, as Dave has alluded to. If using a volt amp meter to read the power and it is working through a PWM charger you will NOT get anywhere near what the panel is capable of. ONLY if using a true MPPT charger which holds the panel at or near max power voltage while the current is being produced will you be able to roughly determine what it may be capable of. Then the voltage x amp will see what it can do. PWM to MPPT can be a lot different and power value delivered to battery will be quite different.
If the panel gets HOT then the resistance is more and the output is less, never expect any more than 60% of stated. It isn't hard for a panel to make voltage, but making current is much harder.

Yep, its easy to get stung with solar.
I've bought many 60W and 100W glass solar panels and never had a problem - always measured short circuit current and open circuit voltage in the beautiful SA sun. The glass panels have all delivered the claimed output.
So a few months ago I took a gamble and bought a 250W 3 panel folding lightweight panel - I thought no way could you get 250W out of panels that were 1580x 680 unfolded. But the panels were the only ones I could find that fitted perfectly where I wanted to store them, only weighed 7kg and were cheap at $200 so I bought them. And sure enough they only deliver 150W when tested. The seller didn't have a clue and offered a refund or compensation, but I figured that panel still fitted my requirements so I kept it. And at the recent 4wd show, I saw the same panels from a reputable company being sold as 150W - so the Ebay sellers just up the figures to get a sale.
I've also had a 100W flexible panel a few years back and it overheated and went zero output in the Kimberley sun.
And a very good friend has replaced the 100W flexible panels twice on his $100k hybrid van. That company no longer uses flexible panels - gone back to glass.

Qldcamper,
Your rather discourteous answer to my original post on this string was a little out of line. Here is the solar setup on my home built caravan;



It's obvious that you already have an MPPT controller. But is is critical to have an air gap under all flexible solar panels to allow them to keep cool. This ensures longer life and proper performance. In fact Kimberley Karavans have had a lot of solar panel failures due to sticking their panels straight onto the bodywork.

I think you have been sold a pup on ebay and are now hopefully wiser for the experience, if not better mannered.

Keith

I am pretty loath to reply to this thread but I must say I have learned something.
I have a "250Watt" flexible panel to which I have added a very light frame made of 1/4 inch aluminium U channel stiffened with Sikaflex and made a stand for it. It is 1100x1000 so is most likely around 150actual watts. ( from the formula in the thread)
The main reason I bought it was so that I didn't have to take up space under my hard floor camper trailer bed like my folding 150Watt panel , and reduce the weight involved as I can lay it flat on the bed..
It fulfils my objectives well, although I used it to replace an earlier smaller flexible panel as the earlier panel gave only about 6amps through my GSL 12amp MPPT controller.
I am currently? running a Century 100AH wet deep cycle battery and I find that the panel charges to 14.3or so then reverts to about 1 amp float, rising to say 4 amps as the Engel clicks in.( using an inline amps/volts etc meter between the controller and battery) I have found the wet battery to be a problem due to the slow take up of amps once near full charge, as you start the next day at a lower SOC than if say an AGM battery had taken charge quicker. I plan to replace the wet battery when its capacity reduces to say 60% as it will not die on me.LOL. It is at 80% after 2.5 years.
So what I am saying is that it is "horses for courses" and as long as you recognize that MOST panels are nowhere near their rated specs , it is not really a problem as there are also other issues at play such as controller, battery type, convenient size and shape.
Panels are so cheap these days that to overspec is pretty cheap.
Ironically I was initially worried that the "250watt" panel would overstress my GSL MPPT 12 amp controller, but it is unlikely that the panel will produce over 10-11 amps even with the battery under 12volts. BTW I can recommend the Australian built GSL MPPT controller and they have great service backup. You are able to call a tech and discuss your concerns.

.

Interesting thread

Always thought the rated (advertised) output of any panel was calculated from the short circuit voltage, if that is indeed the case, no panel will output its rated capacity once regulated down, that coupled with a few losses , if you get 60% of rating i reckon you have done well.

I’m sure I will be corrected if wrong.

Regards

TrevorDavid