Stung with solar
Submitted: Friday, Jan 03, 2020 at 16:17
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qldcamper
Has anyone else come across flexable panels with no referance to output power on them at all, only voltages.
I bought a couple advertised as 100 watt and the best i get out of them is 53 watts, both panels very close to each other.
If they were advertised as 60 watt units id be happy with them, but I need 150 watts for my requirements.
Am currently trying to negotiate with them but they are not very eager to do much. I have cut the ends off the leads for andersen style plugs so returning them probably isnt an option, but they havent even offered a refund yet.
Probably going to get stuck with them and have to buy a third panel.
Followup##
This is a follow up to a previous thread, it wont be responded to by me, it is simply a warning.
There is an online business selling traveling gear with a name similar to " outbacks" but spelled differently.
I purchased 2 flexable panels advertised as 100 watts. The panels had no reference to output on them at all in amps or watts.
Unhappy with their performance i asked them twice how they ascertained they were infact 100 watts as they advertised to which I received no answer.
All they do is say they can be returned according to their returns policy, but I had to change the plugs in order to
test them so they fell outside their returns policy.
Beware, this business is very deceptive with their advertising.
Reply By: Keith B2 - Friday, Jan 03, 2020 at 16:42
Friday, Jan 03, 2020 at 16:42
Are they mounted on anything and what sort of controller are you using?
Keith
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 16:45
Friday, Jan 03, 2020 at 16:45
Thanks for your concern Keith but I am more than familair on how to
test panels hence the reason the thread isnt titled " how do I
test solar panels"
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Follow Up By: Dave B18 - Friday, Jan 03, 2020 at 17:20
Friday, Jan 03, 2020 at 17:20
Qldcamper obvious you are *clueless* how to
test solar panels.
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 17:32
Friday, Jan 03, 2020 at 17:32
And what makes this so obvious Dave?
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Reply By: Dave B18 - Friday, Jan 03, 2020 at 17:19
Friday, Jan 03, 2020 at 17:19
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.
AnswerID:
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 17:38
Friday, Jan 03, 2020 at 17:38
Ok, so would 50% be an acceptable output in your opinion? I have always been happy with 75%
Please share the formula for surface area.
Both panels together are only 2/3 the size of a 180 watt household panel.
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Follow Up By: Dave B18 - Friday, Jan 03, 2020 at 19:54
Friday, Jan 03, 2020 at 19:54
If the panel is crystalline calculate the area and divide by 70.
For example if panel is 900mm x 600mm/70 and will be close to 77W. Depending on the efficiency of the solar panel affects the calculation - not enough in your case to be an issue.
To
test a solar panel for output the best way is to have a multimeter of sufficient capacity (usually 10A) and and put the meter on the 10A setting and short out the solar panel. You cannot damage the solar panel doing this, in fact the way they are factory tested. Always tested every panel that way prior to installation with a factory
test setup.
Even with all my experience at peering at the sky and guessing what I expected the solar radiation to be, seldom was I close. Some days I would guess close to perfect and was hopelessly wrong. Other days you would look and expect the meter to read around 600W/m2 and you would get 900W/m2. In winter 600W/m2 would often be good solar insolation. When you get clouds with the silver lining you can in fact get up to 120% output.
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 09:14
Saturday, Jan 04, 2020 at 09:14
Thanks for that, very useful information.
Obviously you have good hands on training in the field and it is always good that such people speak up even though they get shouted down by armchair experts.
And you were right as it seems, i did not realise the facts about sunshine isnt sunshine as your experience has pointed out.
Always good to learn from someone that has had a lot of practical experience.
There are a few people on this
forum like myself that have had many years of experience in different fields, but in areas that we have had none we can only work in theory and can usually get close. Some listen and learn and some argue that their theory has to be correct and refuse to accept that there are people that actualy work in that field with differing facts.
Thanks for taking the time to share your hard earned knowledge.
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 09:38
Saturday, Jan 04, 2020 at 09:38
By the way, using the over all measurement of the panel including the border it comes up to 72.6. Roughly what i estimated their rating that id be happy with. No way are they 100 watt.
Thanks again for your help.
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Reply By: RMD - Friday, Jan 03, 2020 at 17:44
Friday, Jan 03, 2020 at 17:44
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.
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 17:58
Friday, Jan 03, 2020 at 17:58
I didnt really want to enter into this but...
Even with no reg at all straight into a 12 volt system with a resting voltage of 12.1 and then turn on the waeco the very best i get is 3.9 flashing 4 amps on an accurate clamp meter at a panel voltage of 13.3.
Through a victron 75/15 both 100 watt panels connected in series with a 15 amp load on the battery still only see 7.2 amps from the reg, so still about half advertised power.
Individule panels shorted just over 4 amps with panels facing directly to the sun on a low 30 degree day.
No matter how i set them up consistantly come up with close to 50 watts each.
Like I say, if they were advertised as 70 watt panels i would be happy.
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Follow Up By: Peter_n_Margaret - Friday, Jan 03, 2020 at 18:30
Friday, Jan 03, 2020 at 18:30
"Both panels together are only 2/3 the size of a 180 watt household panel."
Then I would not expect them to be more that 60W each nominal?
200W (nominal, at standard conditions) per M2 is a good starting point. Do that calculation and let's have the result.
"No matter how i set them up consistantly come up with close to 50 watts each."
That is a very good result from the panel area you have?
Cheers,
Peter
OKA196 motorhome
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 18:42
Friday, Jan 03, 2020 at 18:42
Oh they work ok for their size and weight, just not what i paid for.
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Follow Up By: Peter_n_Margaret - Friday, Jan 03, 2020 at 18:46
Friday, Jan 03, 2020 at 18:46
"If it sounds too good to be true …….."
If you bought them on Ebay, you can get your money back.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: qldcamper - Friday, Jan 03, 2020 at 18:56
Friday, Jan 03, 2020 at 18:56
Not on ebay, but did use paypal. Give them a chance though.
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Follow Up By: Dave B18 - Friday, Jan 03, 2020 at 20:02
Friday, Jan 03, 2020 at 20:02
I still help others out and recommend a few panels. Not easy today to find under 200W panels that are what they are advertised as, and importantly efficient and
well made. Generally stick to one
Melbourne supplier. No different to trying to buy 2kW diesel heaters off eBay. Most are trying to palm off 5kW heaters as 2kW. Been going through the exercise this past week trying to find 2kW heaters to help out people. Because they pinch pictures and details off other sites on eBay, they have a 2kW heater advertised with 5kW pictures, and in one place dimensions for a 2kW and another place dimensions for a 5kW heater. eBay is great if you know what you are buying.
Edit. I always ask people with expertise in an area I don't have before I buy most things of value. Cannot understand why more people don't ask prior to purchasing items/equipment of value when they have zero or minimal knowledge or expertise in what they are buying.
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Follow Up By: RMD - Friday, Jan 03, 2020 at 23:00
Friday, Jan 03, 2020 at 23:00
QLD Camper
If you connect the panels directly, for a
test as you call it, you are dragging the panel voltage to close to half of what it performs it's maximum output. Therefore the current ability may be delivered but the energy factor of the voltage being just above battery means the energy available isn't being used efficiently at all. As mentioned, energy to the battery is a product of voltage multiplied by the amps output. If used as such, the panel of say 18V maximum while under load and a panel current of 4amp equates to 72 watts according to electrical theory. I don't know what a 75/15 Victron actually is, but if it isn't an MPPT unit then the panel voltage will still be dragged/held to close to battery voltage,
well below max operating panel voltage and the amount of actual energy will be far less being delivered to the battery. it will eventually charge though. Knowing full
well Ebay panels are sus in many cases I bought one which was stated at 160w. It delivered, on a short circuit
test such as yours, with just 1 amp more than an older 80w panel I had for 6 years. I didn't expect it to be much different to that so wasn't surprised at all. Cheap it was.
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Follow Up By: Member - Boobook - Saturday, Jan 04, 2020 at 07:17
Saturday, Jan 04, 2020 at 07:17
RMD is on the money Qldcamper. I don't think any of your tests are valid tests, especially as you don't mention if you have a PWM or MPPT charger.
"Even with no reg at all straight into a 12 volt system with a resting voltage of 12.1 and then turn on the waeco the very best i get is 3.9 flashing 4 amps on an accurate clamp meter at a panel voltage of 13.3."
Even if you had a 1 million watt panel, you woudl get the same results. The Waeco will never draw more than about 4 amps and you are dragging the panel voltage down. You are only testing the power draw of the fridge in this
test.
'Through a victron 75/15 both 100 watt panels connected in series with a 15 amp load on the battery still only see 7.2 amps from the reg, so still about half advertised power'.
Where is the load? If you have a fully charged battery with a 15A load then the panels may just be topping up the battery and 7.2A may be normal even for 200W of solar. If your charger is PWM then 7.2A x 13.8V = 99.36. Hmm. If it is PWM then you could have them in series but the charge voltage will always be the battery voltage. The extra capacity is lost as heat.
'Individule panels shorted just over 4 amps with panels facing directly to the sun on a low 30 degree day'
This could mean anything. Normal behaviour, hot panels, poor cabling, or even underperforming panels.
No matter how i set them up consistantly come up with close to 50 watts each.
Like I say, if they were advertised as 70 watt panels i would be happy.
I note that you don't mention the open circuit voltage, maybe they are 24V panels.
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 08:32
Saturday, Jan 04, 2020 at 08:32
This post has been read by the moderation team and has been moderated due to a breach of The Foul Language Rule .
Forum Moderation Team
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 08:56
Saturday, Jan 04, 2020 at 08:56
This post has been read by the moderation team and has been moderated due to a breach of The Personal Attacks Rule .
Forum Moderation Team
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Follow Up By: RMD - Saturday, Jan 04, 2020 at 10:02
Saturday, Jan 04, 2020 at 10:02
qldcamper
Is your regulator a MPPT or PWM. It makes a BIG difference if measuring the delivery to the battery. You haven't let us know this fact yet. If battery is 12 and current measure with your clamp meter is 4 amp then only 48 watts is being delivered/available to the battery. Quite a bit less than 72 watts don't you think? If you haven't realized this then perhaps you do need to discover ohms law and energy conversion factors. Have you tested each and EVERY conductor, end to end for voltage drop. Cables or connections may also be limiting your energy delivery. again ohms law related.
It is unfair to attack anyone who tries to guide you with proven concepts which they know to be true and real, when you suddenly reach the limit of your understanding and then rudely cast aspersions upon others. All that shows is a degree of ignorance and unwillingness to learn. You are the only one who is fighting!
PS They are flexible panels not flexable panels ie, flexi, not flexa and the reference to them should not be referAnce. The connectors are Anderson not AndersEn. Rough enough for some Aussies though. The spoken word when written suddenly reveals what a dictionary can rectify. Didn't know a dictionary is a rectifier did ya? Ohms Law everywhere.
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Follow Up By: Member - Boobook - Sunday, Jan 05, 2020 at 06:37
Sunday, Jan 05, 2020 at 06:37
qldcamper,
I apologise for trying to help you. You obviously think you have the skills to address this and insult people who genuinely try to help.
Good luck.
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Follow Up By: ModSquad - Sunday, Jan 05, 2020 at 06:57
Sunday, Jan 05, 2020 at 06:57
qldcamper its not the done thing to ask a question and then denigrate respondents, call them names and use foul language just because your SPECIFIC question isn't answered within your self created parameters. This is the type of poor behaviour that will earn you a ban in the future. This thread is now locked.
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Reply By: Phil G - Friday, Jan 03, 2020 at 22:40
Friday, Jan 03, 2020 at 22:40
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.
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Reply By: Keith B2 - Saturday, Jan 04, 2020 at 06:31
Saturday, Jan 04, 2020 at 06:31
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
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 10:12
Saturday, Jan 04, 2020 at 10:12
Appologies for being abrupt.
I just get over forums sometimes.
Ask a question and never get an answer, just scrutinized.
I had already drawn to my conclusion and was simply trying to find out if anyone else had found panels with no output rating and if so by the same supplier and their results in dealing with them.
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Follow Up By: Batt's - Saturday, Jan 04, 2020 at 13:15
Saturday, Jan 04, 2020 at 13:15
I must have overlooked where you mentioned the suppliers name so I or others can
check their panels.
Also what is your back ground you were pretty strong in mentioning that people don't know what it is but you never actually said what it is which may have helped. Just thought if some solar or electrical trades qualifications then you would have done the correct checks before purchasing the panels then you wouldn't have gone off at others who went out of their way to try and help oh
well.
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Follow Up By: qldcamper - Saturday, Jan 04, 2020 at 13:40
Saturday, Jan 04, 2020 at 13:40
Thats because i havent mentioned the brand or supplier yet.
To the rest of your post.... none of your business so pull your head in.
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Follow Up By: RMD - Saturday, Jan 04, 2020 at 16:48
Saturday, Jan 04, 2020 at 16:48
Batts
One must never challenge ones beliefs eh? otherwise when confronted some immediately get off their bike. As you said, Oh
Well.
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Follow Up By: Batt's - Saturday, Jan 04, 2020 at 22:49
Saturday, Jan 04, 2020 at 22:49
Might have an expert background fixing bikes as
well thanks to the internet.
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Reply By: Rangiephil - Saturday, Jan 04, 2020 at 13:26
Saturday, Jan 04, 2020 at 13:26
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.
.
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Reply By: TrevorDavid - Saturday, Jan 04, 2020 at 20:21
Saturday, Jan 04, 2020 at 20:21
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
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Follow Up By: RMD - Saturday, Jan 04, 2020 at 21:30
Saturday, Jan 04, 2020 at 21:30
Trevor David
The short circuit voltage will be ZERO. However, the current should be max at that time and a little above the actual achieved when the panel is at peak operating voltage . Both short circuit current and Open circuit voltage will be a little more than when delivering peak energy capture and output With an MPPT reg controlling the peak power point.
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Follow Up By: TrevorDavid - Saturday, Jan 04, 2020 at 21:59
Saturday, Jan 04, 2020 at 21:59
Sorry RMD, got my turds all wangled,
The rated terminal voltage of a 12 Volt solar panel is usually around 17.0 to 18 Volts, it is this figure I thought solar panel ratings are calculated from,
before a reg is introduced, hence the reduced outputs from rated.
TDB
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