Thread: Any experiences with ebay flexible panels

Originally Posted by PhilipA

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I am now in a bit of a quandary. Do I buy a 240watt panel which may only give say 8 amps or may give the listed 13 amps which is over the capacity of my MPPT controller.

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Hopefully someone else will chime in here too, BUT!! I'm sure you can input more amps into the charge controller than it's rated spec, just that if you do input more amps, you just don't get those amps out.

So if you had 13amps at any point into your 10 amp controller, you won't damage anything, it just limits current to 10 amps out(discounting any losses here for simplicity).

What you can't do tho is input more voltage than the prescribed open circuit voltage rating on the controller!

That is, if you had multiple panels and wanted to do multiple connected panels for more volts/current, then you wouldn't run them in series as it will increase voltage .. and possibly kill the MPPT.
But, if you did so in parallel, then you maintain the voltage(22v or whatever) but have access to more current in an ideal situation.

I think the idea is that if you run the panels in parallel, then in less than ideal conditions, you still get good current anyhow.
This second notion is similar to your idea of getting a 240w panel .. it'll still be 22voc, but will give you your 13amps .. same as two 120w panels will.

.. anyhow! that's the way I taught myself to understand it all just by reading bits all over the place. Of course I may have it totally wrong.

Which MPPT controller do you have .. could help someone with more knowledge to offer better insight.

Originally Posted by AK83

Hopefully someone else will chime in here too, BUT!! I'm sure you can input more amps into the charge controller than it's rated spec, just that if you do input more amps, you just don't get those amps out.

So if you had 13amps at any point into your 10 amp controller, you won't damage anything, it just limits current to 10 amps out(discounting any losses here for simplicity).

What you can't do tho is input more voltage than the prescribed open circuit voltage rating on the controller!

That is, if you had multiple panels and wanted to do multiple connected panels for more volts/current, then you wouldn't run them in series as it will increase voltage .. and possibly kill the MPPT.
But, if you did so in parallel, then you maintain the voltage(22v or whatever) but have access to more current in an ideal situation.

I think the idea is that if you run the panels in parallel, then in less than ideal conditions, you still get good current anyhow.
This second notion is similar to your idea of getting a 240w panel .. it'll still be 22voc, but will give you your 13amps .. same as two 120w panels will.

.. anyhow! that's the way I taught myself to understand it all just by reading bits all over the place. Of course I may have it totally wrong.

Which MPPT controller do you have .. could help someone with more knowledge to offer better insight.

I run a Victron 75/15 75v/15amp.....given I have two massively under performing panels and one performing near its rated output over all I’m under

Which MPPT controller do you have .. could help someone with more knowledge to offer better insight.

I have a GSL 12-1 which is capable of 12 amps but also can handle two panels in series. You connect to the battery first and it works out whether to charge at 14 volts or 28 volts.These are well regarded Australian Made? real MPPT controllers.

Up until now I have run my 120Watt folding panel in series and it gives up to 7amps measured by my ABR inline meter, but usually 6.5 amps which AFAIK is very good for a 120Watt panel.
That is why I was gobsmacked with the 2.1 amps out of the supposed 150Watt panel.

I think that there was something wrong with the panel as it was split into 2 circuits in parallel and one gave 20.7 volts no load and the other only gave 10.4. There were three terminals of which 2 were positive into the positive lead.

Regards Philip A
But I am tired of the ****fight when the panels don't perform. I spent lots of time , took photos, answered 25+ emails , to be told at one stage that an "expert" said 2amps was normal! from a 150watt panel. Amazon have 100watt panels from Allpowers which seem to be OK , but the youtube review is by some dumb yank who talks about volts not amps.

Over twenty years ago I was in the US during early winter.I noticed many of the cars parked at bus and train stations had flexible solar panels sitting on the dashboard. These were sold at all the auto parts shops like Champion Auto Store. You rolled them up like a newspaper and put in the glove box when not in use. Batteries don't like the very low temperatures in the snow belt (neither do I) so commuters used these things. No idea of their output but they were very popular. Friends in Omaha didn't have a heated garage but they plugged their cars in to block heaters and trickle chargers at home.

I have zero experience with these portable solar panels, but if they are anything like the smaller ones you can use on electronic projects like solar garden lights, then flexible isn't a good idea if they are going to be moved around a lot, especially in cheaper panels. They are very prone to internal damage where the cells are connected together.

After I got my refund from the first seller, I saw a demo semi flexible 150W panel on ebay for $180.

I had previously called GSL and talked to a very helpful "nerd" who advised/explained that 150W was the largest panel my 12-1 GSL MPPT could handle, as if the voltage of the battery was at say 12volts , then the current would increase to 12 and a bit amps.

The panel is a monster with 48 cells and is about 1.5 x 1.2 metres.

I tested it out in my conditions at home, and there is nowhere I can get full sun. However with a tree trunk and some leaves blocking a full line of cells plus another 5 or 6, I was getting 2.5 amps. This is in my experience a good output.

The Voc is 29Volts!( measured ) while the vendor reckons Vmp is 22volts So the GSL MPPT will love it and I should get at least 8 amps.
The vendor fibbed a bit saying it had only been used one hour as a demo, as it had obviously been mounted by marks on the screw holes on it and one eyelet missing.

BUT remember my motivation is to save weight in my camper trailer and to be able to lie it flat on the bed. I have made legs out of 3MMx20MM aluminium strap, and at least in the cool it doesn't sag. I can always brace it with a bit of strap if necessary.
I am happy with my purchase.
Regards Philip A

Hey if it works for you (and it’s safe) that’s all that matters.

I recently finished the solar and charging set up on our Xplorer and it’s the single best thing I’ve done to it.

No more concerns about power reserves, it’s overcast as heck today and there’s no issue at all.

Reading this thread it seems to me that what is totally misunderstood here (again) is the basic electrical fact that current is taken not given. The amount of current taken in a solar battery charging scenario is determined by the voltage supplied by the solar regulator and the state of charge (SOC) of the battery ie. load. The amount of current taken is not a definitive measure of the capacity of the charger or solar panel(s). If the battery is fully charged (ie. no load) then the current flow will be minimal and if the battery is flat the charging current will be greater but may not be an accurate measure of the system capacity.

There is one way and one way only to measure the output of a solar panel.

1/. Place the solar panel to be tested in full sunlight perpendicular to the sun.

2/. With no load on the panel measure the open circuit voltage (Voc) of the panel. This should be the same as the stated Voc in the sticker on the back of the panel.

3/. Using an ammeter with a capacity that is greater than the short circuit current (Isc) given on the back of the panel place the ammeter probes on the output terminals of the solar panel. This may seem a bit drastic as doing this to any other generating source will result in much spark, flame, smoke etc but this is how you measure Isc of a solar panel.

Solar systems are about generating power and transferring that power to a battery or other load. The voltages and currents between the panel and solar reg are not constant, they vary depending on a number of circumstances and equipment types. What is important is the generation and transfer of power from the panel to the battery (load).

To really test out your solar setup try doing something like this.

1/. Connect a fully charged battery to your solar reg.

2/. Set up your panel(s) in good direct sunlight and connect to solar reg.

3/. Connect a load to the battery/solar reg that is equal to or slightly greater (measured in watts) than the output of the panels (also measured in watts). Headlights/driving lights are good for this.
note. if the load is fed via the reg as in the OP's case don't exceed the regs maximum current specs.

Measuring the output voltage and current from the panels (and multiplying the figures together) will give you the real world maximum power (in watts) your system is capable off generating. IMO if you achieve 80% of what the panels are rated at you're doing very well.

Again, solar systems are about the generating and transfer of power (measured in watts). Values of voltage and current can vary greatly especially between the panels and the reg and don't give a true indication of the capabilitys/performance of the system.

Deano