diy solar

diy solar

Looking for opinions on Canadian Solar Brand panels.

I'm for sure i'd need a 2nd charge controller, but i gotta do some drawings to see how i can arrange the panels on my roof..and still use my same home made racks on the roof,
I'd attach a picture, but i can't figure out yet how to do so on here.

my old panels are probably 15 yrs old, or so,, i bought them used.. but my calculations and quick test the other day. i tested all 3 strings. they were
they were consistent with each other. seems still 100% good, i measured open circuit voltage and short circuit current. I know they can't still be 100%
The short circuit current was a bit low. but still very good. they are Photowatt brand.
M-PW1000 24V ( PW1000 24V ) SIZE bout 26 1/2 X 52 3/8 and bout an inch thick.
web page >>------> http://www.posharp.com/photovoltaic/database.aspx?ctype=10&cid=a4c61fe1-5065-4d3b-bb6d-252580ba4dc3
Mine have the M in the model, But on the page the M is not shown, but others with same spec show.

I did some load test the otherday. I have 3 strings of 8 in series
OCV ISC calculated watts
string 1- 287v 2.95 846
string 2- 277v 2.96 819 -------------------------------->>> each string is 8 panels in series @ 24V
string 3- 289v 2.84 820
--------------
2485 watts can this be right ?
 
Open Circuit Voltage is at no current, so zero power. Short Circuit Current is at no voltage, so no power. But those tests do show they are functioning well. To get the real power, you would have to adjust the load and find the maximum power point. Typically the voltage will be pulled down to 75% to 85% of the VOC, and the current will be about 85% - 95% of the ISC, but it all depends on how much light is hitting them, and how efficient the cells are at the moment. This is where an MPPT unit does it's job. It constantly varies the current while measuring the voltage, to find the peak power. I am not able to open the page you linked in your post. Did that page list the original VOC and ISC numbers? That would be the best way to see how close they are to when they were new. But to get those numbers, the panels would have to be at STC conditions, which is not really possible. STC is perfect full sun at 90 degrees to the panel face in a cool 25C temp.

Here are the numbers for the Canadian Solar 295's.

VOC = 39.5 volts
ISC = 9.75 amps
Multiply those and you get 385 watts. Way more than the rated 295 watts in perfect STC conditions.

The maximum power at STC works out like this

VMP = 32.3 volts 82% of VOC
IMP = 9.14 amps 94% of ISC
Multiply those and you get 295 watts, the STC rating.

It is not really possible to guess the MPP from just the open voltage and the short current, but if we use the same ratio from the Canadian Solar ones, we see they did almost 77%. Your old array did 2485 in the open V x short I test, So 77% of that is about 1,913 watts at MPP. or just about 38 watts per panel. That is not great. But of course this is a shot in the dark of the real MPP power, and when was the measurement taken? Was the sun dead flat on the panels or was it late in the day at an angle? The STC 100 watt rating is "perfect conditions" so expect the real power to be only 90% or 90 watts per 100 watt panel at the very best.

In real world conditions, they should list a PTC power rating. The PTC rating on the Canadian Solar 295 panels is a more realistic 270 watts. That is actually very good at over 91% of the STC rating. Most are a bit lower than that. A REC Solar 340 watt panel drops to 257 watts hot rating. Just 76%. That seems very low, but it is at a very hot 45C rating at 80% sun. A Panasonic HIT 325 watt panel does better at 302 watts at PTC. These are claimed to be some of the best hot climate panels, still making 93% at 44C, but I think they used full sun still. That is probably true on the Canadian Solar ones as well.

You have to check all the fine print to make sure you are comparing the same specs. PTC and STC are pretty well standardized test. The REC panel did not list a PTC rating, only the NOTC 45C temp at 80% sun which is a good real world estimate of what you should get.
 
ok,, here is the closest data i can find for my old panels ( Photowatt M-PW1000 24V )
I do remember that when i had my grid tie inverter, the max i ever seen it produce was about 1850W
I don't know the age of these panels, unless you can tell by a serial number or such.

IMG_20180128_205814997.jpg
 
Looks like your panels are the 24 volt version. Your string one was 287 volts with no load, divided by 8 panels is only 35.87 volts. That is down quite a bit from the rated STC 43.2 VOC number. So I am guessing the sun was not directly square on the panels. The short circuit current in full STC sun should be 3.15 amps, you had 2.95, so closer, but still low. The panel in this picture has a date mark of "Q3-02". That would be 3rd quarter of 2002 which is 18 years old. It is nice that it even states the 100 watt rating are at 25C and 1000 W/m2, which is theoretical full sun. 80% of that is much more typical. My array tops out at about 3800 watts AC after the inverters that are 96% efficient. So a theoretical DC input of 3960 watts or so, out of 16 panels, so 247 watts per panel. That is right at 80% of the STC 300 watt rating.

If you were topping out at 1850 watts for the whole array, that is 77 watts per panel. That is very close. Figure 95% efficiency in the inverter, and the panels were making 81 watts. Again, 80% of STC is very good.
 
Thanks,, that's a lot of good info .. I had no idea on how to figure out the date code. or where it was located,, but now that you told me, I can find it on the sticker now (Thanks)
As for my panel readings, it was nearly noon or somewhere in the peak range for my 5hr peak sun area.
Some of the panels I have are 12/24v selectable.
Do you by chance know what the "M" prefix is in the model number? Most i found online were just PW1000.
 
Do you by chance know what the "M" prefix is in the model number?
On solar panels, and "M" usually means "Monocrystalline" cells. They are a bit more efficient and have beet high temp specs than poly types.
 
Cool.. so i have better panels than i thought..

I started using a few of the Canadian panels I got,, built me a home made rack out of salvaged sign post tubing.
I'll post pictures in a bit..
 
Ok,, here they are... Only could get 3 of them on this rack, I'll use this one for projects.
 

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Looks pretty good. Those are 60 cell panels, very similar to my Sil Fab M300's. Make sure they are actually bolted down. It would not take much wind to lift one off the rack. Iron Ridge has their UFO clamps that bridge across between the panels and clamp them to the rail below. They also act as the grounding connection.
 
They are clamped down.. My clamps are home made.. basically a bolt with a large fender washer, and 2 bits of thick rubber hose to act as bushings
when i snug the bolts down they squash the rubber bushing, making it expand a little and fill the gap between the panels.
the bushings are a bit longer than the panel is thick. so they seem to do well..
I did this with my panels on my roof, they been thru 3 hurricanes and no issues.
I have acquired another large panel. I'll start another thread on that one..
 
GXMnow >>> for now, I'm just going to use 9 panels..
I can't fit to many on the roof right now,,
I think if ireuse my home made rack, the new panels won't fit right, unless i drill some holes, because the tubing is actually sign post..
SALVAGED.. The holes are spaces @ 1" intervals. I think you saw my old panels somewhere else in the forum here..
I'll keep you posted..
I scored my a nice big metal enclosure, this will work for another small solar project i started.. 3x 295w panels, 50A mppt charge controller, a 1400va UPS that will be my inverter.
I can house up to 6x 120AH SLA batteries in it
I plan to have both boxes under the ground mounted rack i built..
Also from sign post... Lol its sturdy as hell.
And both boxes are NEMA3 or better
Freebies.. Actually the UPS was a dumpster find.. Only needed batteries
 

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