Portable Solar Power Panel

[muDped]

Solar Power is an effective source of free electrical power and innovators in manufacturing are continually producing new devices for our convenience.

135 Watt (Maximum) Portable Solar Panel

This device is presently on sale for a short time and the specifications are impressive.

Thoughts anyone?

Does it look to be a useful device at a good price?

[gyula]

Hi muDped,

Very likely the 135 W output comes at a direct sunshine reaching perpendicularly the full surface area of the panel.  Still it seems to have an  impressive performance and its output USB sockets plus the a separate DC output make the device a versatile power source.

Inspired by this solar panel, I found this offer at ebay: https://www.ebay.com/itm/164977048061 
It has only a single 12 V output though and the claimed output power is at 300 W. It needs a separate step up DC-DC converter for operating a laptop or a step down converter to have 5V DC outputs.

Here is another solar panel offer, with max 18V, 300 W power output    https://www.ebay.com/itm/174858538347
and this offer includes an optional high current capable controller, see the item C and D options with the prices changing accordingly.
The controller can be had separately without the solar panel as item A option. 

I noticed the conversion efficiency of the panels are claimed to be 21% for your bangood offer, 23% ±1% for the first ebay offer and the 2nd ebay offer specifies it only as 'high',  all the 3 offers have Monocrystalline structure which is already an advanced development. 

Greetings
Gyula 

[muDped]

Yes, the present trends in Solar Panel production are something to behold.

The prices for the panels you've found on Ebay are incredible.  Solar power is now more affordable than ever!

Well, I've gone ahead and ordered one of the panels from Banggood for evaluaton.

We shall see.

[e2matrix]

Banggood is generally fairly reliable in their product descriptions.  But that one mentioned on eBay is totally bogus.  There is no way a roughly 12" x 17" solar panel is putting out 300 watts.   Probably about 30 watts.  And getting 300 watt solar panels for that price is unheard of.   The other one listed is a controller for solar panels and might be valid but the last used solar controller I bought was a steal at $100 (Trace / Xantrax brand).

[Paul-R]

Hi muDped,

Very likely the 135 W output comes at a direct sunshine reaching perpendicularly the full surface area of the panel... 

...situated on the equator.

The 300w people do say in the tech description 201w - 300w. The ultra thin bendy ones are interesting. It might be possible to fix them on the upper surface of a 2-seater aircraft wing but they would need to be removeable. One wouldn't want them tearing off in a steep turn.

[muDped]

The Portable Solar Panel has arrived.  Now I just need to accomplish some testing and evaluation.

[Allcanadian]

I was looking at the "Canadian Solar" panels a while back better suited for colder climates. They were a 300w panel having 60 cells I believe and were 36" x 48". So I find it hard to believe a 12" x 17" panel could put out 300w.

I designed my own MPPT charge controller which definitely helps with output. Many older controllers have a high cutoff so the sun can still be shining but the system is in idle mode. My system could keep generating from starlight/moonlight down to 1 volt or less. So if a person is going to pay for panels then we should try to wring every last watt out of them. More so when the system could be in operation for decades.

My system used a microcomputer to switch CUK (step up/down) converters. Big converter for big power then smaller, high efficiency converter for the low power end. It just monitored the voltage/current and switched converters in or out based on the power output. My thinking was that a cut out was basically pointless given that the array always seems to be generating some power even at night, why not utilize it?.

Regards
AC

[partzman]

The Portable Solar Panel has arrived.  Now I just need to accomplish some testing and evaluation.

If you possess a digital scope capable of taking instantaneous math measurements, you can simply charge an inductor of 50-100mh from the output of the panel and take a voltage measurement acros the inductor and the current thru the inductor.  The peak power as indicated by math calculation will not only give the maximum power for that sun but if you record the voltage and current at the peak power, you can then calculate the resistance which is the resistance needed for MPPT or maximum power point at that sun.  You can also use a lower value of inductance but the power readings will begin to increase due to the non-linear capacitance of the panel.  The inductor must not be allowed to saturate during this test.

Normal maximum ratings for a solar panel are given at what they term 1 sun.  I too don't not believe that your panel will come anywhere close to 300 watts, perhaps 30 watts for that size but we shall see!

Regards,
Pm

[Allcanadian]

It's also important to be objective and see things for what they are in reality...

A solar panel is made of solar cells which act like large surface area diodes. EM radiation from a nearby star causes the free electrons in one (+) plate to become excited and jump the PN junction/diode to the other (-) plate. As such it doesn't matter how the free electrons become excited only that they do and migrate across the PN junction.

All too often people see only superficial objects like solar panels, inverters and wires without understanding the reality of how the process actually works under the surface. I have little interest in what most people do and look at everything conceptually as a process. For example, it's possible to convert a solar cell/panel to a zero threshold detector just like an EPAD mosfet. In which case the PN junction threshold becomes zero and the cell can conduct at any voltage. If the cell can conduct at any voltage then any source exciting the cell in any way can produce a conduction current. 

Regards
AC

[muDped]

I conducted the first testing today as the Sun was setting in the West.

The Panels each delivered 23.2 Volts Open Circuit in direct sunlight, and approximately 19 Volts in the Shade or facing away from the Sun.

With the panels completely folded up and not exposed to direct rays the Panels produced 1.2 Volts.

The Cells are surprisingly sensitive to light at even low levels.

Next tests will be to determine available Power in each of the lighting situations.

First I must construct some sort of Load to evaluate the Panel's capabilities.

[3D Magnetics]

I think that you will discover that the method used by the Chinese sellers is (short circuit current x open circuit voltage) =watts .

A similar incompetent method is used to claim  unbelievable battery capacities. 5000mah is a load left on until the lipo is completely destroyed and amps are measured regardless of voltage .the final phase is at very low voltage . Watt hours would be helpful but it will never happen.

[Centraflow]

These are my panels today, late in the day as you can see.

Each panel is 455w, the open-circuit voltage of 48v, max load voltage 41.5v at 9.8amps

I have 8 panels atm all connected in series, so 332v at 9.8amps is maximum when the sun is direct overhead.

The green area shows the panels performance, the purple area is what I have dumped into the grid, my battery voltage is nearly 100% for night use "5kw". Brown area is when I have drawn from the grid, but I am compensated kw for kw with what I have put into the grid.

I only pay a 10 euro connection fee, I do not buy power from the grid at the end of the month.

I have upgraded my converter which has two inputs, the second will take the STEAP TPU input when I have it stable "from 150v to 600v""

My house is 240v AC

Regards

Mike

[muDped]

Centraflow,

Very nice!!

Free Energy is a wonderful thing and you have an abundance!

Tell us more about your battery system please.

[muDped]

This afternoon as the sun was setting I performed a rudimentary power test of the Solar Panel using an Automotive Headlamp Bulb as the load.

In direct sunlight it powered the bulb to a bright Orange glow.

In indirect light it produced a barely visible glow of the lamp filament.

It was a quick test so I didn't measure voltage at the load or load current.

I just wanted to get some idea of what its capabilities are.

I'll have to build an Electronic Load Device using a Power Transistor or MosFet with both Voltage and Current measurements to perform a more detailed analysis.

I also have ordered a variable Buck Converter to enable a better impedance match to low voltage loads.

[partzman]

FWIW, here is a sim example of the test I described in my post #7 that is relatively simple and most definitive.

This is a sim of an accurately modeled Solar Africa SA-25M PV module that is rated at 25W at 18vmp and 1.39amp.  The "Q" formula is the best fit polynomial for the non-linear capacitance of the panel and the 500 ohm shunt resistance is the best fit equivalent resistance of the panel at 1-sun or full output.

From the sim we see the maximum power to be 25.058 watts at ~3.29ms during the time L1 is charged from the panel.  The voltage and current at this maximum power point is 18.4 volts and 1.36 amps respectively which compute to a maximum power resistance of 18.4/1.36 = 13.53 ohms.

Regards,
Pm

[Centraflow]

Centraflow,

Very nice!!

Free Energy is a wonderful thing and you have an abundance!

Tell us more about your battery system please.

The batteries are auto grade lithium ion, 2 banks of 48v 2.4kw each. Total 4.8kw.

Maximum discharge is to 20%. They have a guarantee of 80% charge density at 10yrs.

Not cheap, but reliable

Regards

Mike 

I have added a photo, the batteries are on the floor atm, will be going in a rack when I have bought one, they are very heavy.