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Solar output

For the folks with solar. Do you ever see anywhere near the max output from your panels laying flat. In theory a 1000W system max output is about 83 amps at 12v. I have 840 watts of older panels, the most I have ever seen is 40 amps or so. My Outback controller is good for 150volts and 80 amps out. I'm wanting to add an additional 420watt panel for 1260 watts potential  105 amp max output.

The question here is what percentage of max output have you seen from your panels laying flat, as I'm not going up on top to tilt panels. I'm thinking 50-60% is about it. What say the gallery, I don't want to melt a controller or add a second one.
 
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Solar output

Reply #1 –
My understanding is that the controllers shed the extra amps if they happen. I have 2030 watts solar and the most I have gotten in the Sierra's in July was 150 amps which came from a Victron 150/70 and a 150/85. Our domed roofs have some panels coming in earlier and the others on the opposite side staying longer. Right now at the Phoenix Raceway the best I got yesterday was 63 amps. This morning I woke up to 55% S.O.S. but the consumption is minus 18 amps and slowly headed for the plus side.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Solar output

Reply #2 –
Quote from: bbeane –
1.  In theory a 1000W system max output is about 83 amps at 12v.
2.  I have 840 watts of older panels, the most I have ever seen is 40 amps or so.
3.  I'm wanting to add an additional 420watt panel for 1260 watts potential  105 amp max output.
Bruce,

I can't answer your question directly, cuz I've never paid any attention to the amps being output by the panels on our coach.

BUT, I can tell you something that I learned during our home solar installation project.  Solar panels don't put out anywhere near as much power as you think they will when you buy them.  This fact bites home solar customers in the A$$ every day.  I hang out on home solar forums and I see the myriad posts from angry/disappointed customers who think they got screwed by the solar salesmen.

Solar panels are labeled with a "nominal" output rating, usually as part of the model number.  I will use the panel we purchased for our home system as an example.  It is labeled "LG380N1C-A6" and is advertised as being a 380 WATT panel.  Any panel you look at will be labeled in this same way, and you might rightly expect the panel to put out what its name implies.  The fact is, it won't.  You will be extremely fortunate if you ever see any numbers above 75% of the nominal rated output.  Hence the source of the home solar customer's anger & frustration.

The spec sheet that should be available for any solar panel helps explain why this is so.  See the sheet for our LG panels below.  There are two output ratings on the sheet.  In the upper right corner is the STC rating, which is always used when the manufacturer names the panel model.  Down toward the lower left is the NMOT rating.  Savvy buyers ignore the STC rating (cuz they know it is bulls**t) and go to the NMOT numbers when designing a system.  Both rating numbers are generated in strictly controlled lab tests.  The NMOT test conditions are simply closer to the "real world" environment, and therefore more realistic.

So, what I'm saying is that looking at the numbers you mentioned above, I would suggest making the following adjustments to your expectations:

1.  A 1000W (nominal) system is best case really only a 750W system with max output of about 62 amps at 12V.

2.  840W (nominal) of older (less efficient) panels would struggle to put out more than 630W and 50 amps, so your reported observations (...40 amps or so...) are right in the ballpark.

3.  Bumping your system up to 1260W (nominal) would at best probably only get you about 945W of actual output at max 78 amps.  I would use this lower number to evaluate the capability of your Outback controller, but that's just my opinion for what its worth.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Solar output

Reply #3 –
Our 1140 potential watt system puts out 700-800 watts best when the sun is the highest. But, our latitude where we do the most camping is somewhere around 38 degrees. If I tilt a panel so it's perpendicular to the sun, the wattage goes way up. But, even if you tilt the panels on your roof, the panels will only be perpendicular to the sun for a brief moment.

Panel temperature also has a lot to do with it. The output of a panel is rated at 25°C or 77°F. As the panel temperature goes up, the efficiency goes down.

Dirty panels produce less juice and system loss because of inadequate wire size also cut the output. 3 percent is the target loss from controller and wiring loss.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Solar output

Reply #4 –
Quote from: Pierce & Gaylie Stewart –
If I tilt a panel so it's perpendicular to the sun, the wattage goes way up. But, even if you tilt the panels on your roof, the panels will only be perpendicular to the sun for a brief moment.
As Pierce notes, a panel oriented exactly perpendicular to the suns rays is best case scenario.  In fact, that is how the panels are tested under both STC and NMOT laboratory rules.  Which is yet another reason why panels underperform their ratings in the real world.  Panels mounted flat on the roof of a RV (or the roof of a house) will seldom achieve perfect orientation to the suns rays.  In most cases, if you desire higher output, the simple solution is to add more panels.  Which works, at least until you run out of space on the roof...  :thumbsup:
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Solar output

Reply #5 –
Quote from: Pierce & Gaylie Stewart –
But, even if you tilt the panels on your roof, the panels will only be perpendicular to the sun for a brief moment.

Panel temperature also has a lot to do with it. The output of a panel is rated at 25°C or 77°F. As the panel temperature goes up, the efficiency goes down.

Pierce

Future advancements will increase usable angle versus output. Will be a game changer. Temperature where these panels are most efficient is never under 77 degrees. Have read articles about cooling the panels. Higher operating temperature panels design. This too will eventually come about boosting efficiency. Once they get these bugs worked out hopefully batteries performance and longevity resolved ill be ready to buy Into solar power.  I use passive solar daily in my shop at home for the past 15 years and it is outstanding. Panels supply domestic heat need 95%. Its like we skipped over basics. Passive solar is not portable. Exciting time we live in.
Scott

Re: Solar output

Reply #6 –
My pair of 410 panels put out around 40 amps at most.
Most controllers will take a lot more stated panel watts  than the specs say. Ie 4 240 watt panels don't seem to overload a 750 watt controller. The amps will be inside designed parameters. In the 750 watt / 60 amp controller


Budget 200% of required wattage and the result will be close . Imho

Re: Solar output

Reply #7 –
Our 4 panels are plenty and go to float well before noon for our 400ah battery bank. Changing everything possible to LEDs made a big difference. And our panels/batteries are going on 14 yrs now.
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Solar output

Reply #8 –
Over the years, I have logged maximum solar amps in Excel, when panels are cool, battery low, clear sky sun above. It seems our 730 watts of solar often reach 65%, few 70%.

Years ago, we tilted, but found that adding couple more panels compensated for tilting no longer...

Our panels were mounted above roof with air flow under.

Re: Solar output

Reply #9 –
My experience is about the same as others. I'm thinking of adding another panel because it probably will never overload my controller which is "theoretically" maxed out. With 900 watts I've seen  800 briefly a time or two. My home run to the controller from the combiner is 2 gauge and not that long. Five 180 watt 12V panels run parallel to combiner mounted with good air flow flat on roof.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Solar output

Reply #10 –
Thanks for all the replies.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Solar output

Reply #11 –
As Bill from Quartzsite would say " too much is just right".

 We no longer budget our power like we needed to before.    Until she turns on the microwave and hairdryer at the same time.  Then it's abuse of power🙂
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Solar output

Reply #12 –
I have 8x380 watt bifacial panels mounted flat on my roof. In June, I had 440 watts coming from one panel while checking to see efficiency. That's 115%. November 1st, the same panel was outputting 330 watts or 86%. Residential panels will output closer to their stated wattage and for longer into the winter.
1999 U320 WTFE #5586
2014 Subaru Forester 6sp
4000 watts of solar
650 aH @ 24v