2x 250 watt panels, in planning stage

cunningstuff · Member

2x 250 watt panels, in planning stage

dorian · Guru

I suspect that the great price will soon be tempered by poor results.

The first problem is the description: "12V 100W 160W 200W 250W 300W Solar Panel Kit Mono Power Camping Caravan Battery Charge USB". So which panel am I buying?

The second alarm sounded here: "Colour: 250W"

Under the Product description we have:

Max Power Current: 13.89A

The max power is therefore ...

18V x 13.89A = 250W

That's OK so far.

The dimensions are 1080x710x30mm.

That's 0.7668 square metres.

At an efficiency of 20% we would expect a power output of 153W.

Now let's look at the weight spec. In fact there are two.

Item Weight 15 Kilograms

So which is it?

Whenarewethere · Guru

The battery you have stated is too light for 100ah. Also its physical size is too large. 330 x 215 x 173 = 12.27L = 0.774kg per litre.

I wouldn't touch it with a barge pole.

A well known & respected manufacturer 321 x 197 x 152 = 9.61L = 1.56kg per litre.

Whenarewethere · Guru

The solar panel figures do not make sense.

1.080 x 0.710 = 0.7668 square metre.

250 watts / 0.7668 = 326 watts per square metre. There must be 2 suns in the sky!

Even if you physical stuck all the solar cells next to each other, on my panels they are 155 watts per square metre. The actual output is 113 watts per square metre. Including dead space around the actual cells.

dorian · Guru

Whenarewethere wrote:
The battery you have stated is too light for 100ah. Also its physical size is too large. 330 x 215 x 173 = 12.27L = 0.774kg per litre.
I wouldn't touch it with a barge pole.

A well known & respected manufacturer 321 x 197 x 152 = 9.61L = 1.56kg per litre.

The specs have errors, as usual.

For example, it would appear that the PLUS versions have half the charge time of the standard versions (1 - 2 hours versus 2 - 4 hours). However the max charging current for the 200Ah PLUS is the same as for the 200Ah.

Also the weights don't seem to increase proportionately.

200Ah -> 31kg

300Ah -> 34kg

The dimensions aren't proportionate, either:

135Ah -> 16.7L

200Ah -> 26.9L

300Ah -> 30.5L

The 200Ah models seem to be out of place.

Surprisingly, the specs for the 200Ah and 300Ah don't make sense to me in Victron's brochure, either (22kg for 200Ah, 51kg for 300Ah) :

https://www.victronenergy.com/upload/documents/Datasheet-12,8-&-25,6-Volt-lithium-iron-phosphate-batteries-Smart-EN.pdf

To the OP, see this thread:

https://thegreynomads.activeboard.com/t66202769/stay-away-from-outbax-camping-solar-panels/

-- Edited by dorian on Sunday 6th of December 2020 09:18:36 AM

Whenarewethere · Guru

dorian wrote:
To the OP, see this thread:
https://thegreynomads.activeboard.com/t66202769/stay-away-from-outbax-camping-solar-panels/

A good thread to read!

If you are buying solar panel mounting pads, often the ones on the internet will say they are ABS plastic. They are not & will not glue properly to the roof & you will end up with a solar panel in a following car's windscreen.

Make sure the solar panel has a machined corner & is screwed together. Not some cheap plastic corner knocked into the frame.

I am using this make, mainly because the small 20w panel would fit in a given space. It has performed above specification. So I believe their is no reason their other sizes would not perform to specification.

https://www.projecta.com.au/solar-panels-controllers-products/yzrdlvu0olyaoqwyfsms1qvvtbzkww

Their 160 watt panel 0.64 x 1.490 = 0.954m²

160 / 0.954 = 168W/m²

I would suggest for a given size of panel this is what one would expect out of it. If a supplier is suggesting much more, they are more than likely using a rubber ruler!

Are you sure the controller you are looking at is actually an MPPT. A Victron MPPT is actually an MPPT & is a lot more expensive.

https://www.batteriesdirect.com.au/shop/product/28091/smartsolar-mppt-100/30.html

While on the subject of using products which will perform as stated. Use quality cable, there is a lot of 70°C cable out there which is simply a fire hazard. Do not skimp on cross sectional area of your wire.

Thin wire, crap solar, non stick pads, dodgy batteries, over heating controller. A recipe for disaster & great expense!

dorian · Guru

@cunningstuff, if you wire your panels in series, then at max power your MPPT regulator will see 36V @ 13.89A. Assuming it is charging the battery at 14V, then the charging current will be 35.7A at 100% efficiency. Therefore a 30A MPPT regulator will be operating at its limit.

BTW, I don't understand your references to 20 ohm loads, nor your 300W fuse.

-- Edited by dorian on Sunday 6th of December 2020 10:58:38 AM

Whenarewethere · Guru

Hot weather, hot van, controller running at its limit. It will de-throttle at 40°C..... or fail.

Even though my 6 x 20W solar panels have a maximum MPPT input of 7.9amps & output of 11.3amps under ideal conditions, well under the 20amp output rating (I upgraded from a 10amp MPPT). I have added additional heat sinks to hopefully keep it well its 40°C de-throttling. If you have a high ambient temperature something has to give!

-- Edited by Whenarewethere on Sunday 6th of December 2020 11:19:29 AM

cunningstuff · Member

Tomorrow I will be putting the multimeter on the panels. We had heaps of rain and then I was busy yesterday, so I will get some readings tomorrow. Should be full sun.

The panels measure 1080mm x 710mm, with 72 rectangular modules 165mm x 55mm inside the panel and weigh 8.o kg on my bathroom scale, which has been accurate enough in the past, give or take 5%.

you can see the back panel on the flikr link in the original post, but it says:

open circuit voltage: 22.5v
maximum power tolerance: -+ 3%
max power voltage: 18v
max system voltage: 1000v
operating temp min: - 40c
operating temp max: 85c
cell tech: Mono-Si
module application class: A
TUV certification: Yes
Net weight: 8.2

One of the MPPT controllers I am looking at:www.amazon.com.au/EPEVER-Controller-Intelligent-Modular-Designed-Triron4210N/dp/B084MCMCQP/ref=sr_1_5%2Caps%2C311&sr=8-5

There is one very similar called Renogy brand, closely related. The reviewers have stated the Epever brand has a beefier set of terminals.

500watts /24v = 20.8ohms + 25% = 26ohms.

cunningstuff · Member

and quickly, www.youtube.com/watch
gentleman using the batteries I am talking about.
He is also using the Epever Mppt controller I am looking at.

dorian · Guru

cunningstuff wrote:
500watts /24v = 20.8ohms + 25% = 26ohms.

That's amps, not ohms.

The specs on the panel are another red flag. They don't mention the output power, nor do they state the current at max power. I expect that you'll get maybe 120W per panel, assuming an actual efficiency of 17%, and allowing for a reduced area due to the frame and spaces between each cell.

-- Edited by dorian on Monday 7th of December 2020 07:00:04 AM

dorian · Guru

The cells in that Amazon panel are rectangular, without chamfered corners. According to Wikipedia, that's indicative of polycrystalline cells (left). Monocrystalline cells (right) tend to be squarish with cut corners. Mono cells are uniform in colour but poly cells are not, although the non-uniformity of poly cells may be masked by a film.

https://en.wikipedia.org/wiki/Polycrystalline_silicon

Poly cells are typically much less efficient than mono cells (17% versus 21%).

cunningstuff · Member

Thanks Dorian, indeed I had those confused. I can always replace these panels after some time, maybe in a year. Right now I will stick with them as I am very restricted on budget due to Sydney rents. After I hit the road I will have more monetary freedom and can upgrade to new levels. Squeezing pennies basically. If the wattage is going to be so low, I will look into just using the 40 amp MPPT.

dorian · Guru

What's really sad is that that particular Amazon seller has a 93% positive rating. This would suggest that the vast majority of people have no idea what they are buying.

Whenarewethere · Guru

I would have used a Victron panel but they didn't have one with the physical dimensions for my design.

Anyway, looking at their panel efficiency, polycrystalline.

90W 172.7W/m² 6.1kg

115W 169.6W/m² 8.0kg

175W 176.4W/m² 12.0kg

Another couple of issues with large panels is their weight, 250W is about 17kg. A pretty miserable thing to handle & flexing issues because the panel is so large.

It would be safer to go for 4 or 6 smaller panels. Much easier if you need to do some maintenance, which invariably happens.

If one panel fails you only loose 1/4 or less of your resources. 2 large panels, one fails & half your solar is gone & no further redundancy.

Whenarewethere · Guru

dorian wrote:
What's really sad is that that particular Amazon seller has a 93% positive rating. This would suggest that the vast majority of people have no idea what they are buying.

I wonder how many of those people know how much power their panels are producing. Simply a guess, probably less than 1%.

Tip:

If you loop the wire though the clamp 4 times & divide the answer by 4 you have a more accurate figure. My DC clamp meter only has a resolution of 0.1 amps.

-- Edited by Whenarewethere on Thursday 10th of December 2020 01:24:48 PM

The Travelling Dillberries · Guru

dorian wrote:
What's really sad is that that particular Amazon seller has a 93% positive rating. This would suggest that the vast majority of people have no idea what they are buying.

Truth be known, probably 85%of the 93% are Amazed they got the product and Amazingly soooo fast too. Certainly the ratings are not performance based.

cunningstuff · Member

I do not have access to a clamp meter like that at this point. I just have a simple multimeter from Aldi. I took a reading that day in the sun .720 from the mA setting. But since I do not know what I am doing at this point in time I have let that be. If I get 200+ watts out of this I will be more than happy for my first year or two. I have a friend who is donating me a 50amp Solar controller and three 100ah deep cycle batteries. They are not lithium just standard lead-acid but they ARE free. This lets me start with 150ah available per cycle for the cost of nothing. I will revisit this post when I have done my test set up, before installation, and have some proper results to pass on. I do hope to find my way in this country by doing this. I need to travel and make friends, and discover myself. I will be in contact, and after install, I will start a new thread to keep updated.

I would like an option of top-grade gear. I would like to have the best available. I do hope that along the way I establish a digital nomad style income or find the trade that is eluding me for my last 12 years before retirement. If that happens, well then custom batteries built off of wholesale cells with 1kw of 48v panels, built into a large used Mercedes trade van becomes a possibility. This is but a sidebar to actually become the nomad I want to be. I have however learned a great deal reading and listening here, so I intend to keep one eye open and one ear to the ground here.

cunningstuff · Member

one more thing, I did just now to assure myself, used high power led flashlight to inspect the cell itself. To all views and descriptions EXCEPT its shape it appears to be monocrystalline. I am used to filters and plastic coverings, it does not have that look to my eye.

cunningstuff · Member

So I was donated a lot of equipment recently. I have a friend who has been a bit bored in life I think. He has donated a 50amp controller, I am betting an MPPT, and 3 x 100ah lead-acid batteries. I will now need to vent the batteries, but to be honest, the savings in money alone is more than helpful enough to complete my build. When I get done repairing the body, I will come here looking for wiring advice. I will get jaw-wag with him this weekend, so I am hoping he has a clamp meter as well so I can get a proper reading of what my panels can do. If not I will research how to get the proper measurement from my multimeter come back here to discuss the wiring setup.