Solar Output in Shade?

On a sunny June 27th this year we camped under the full leaf cover of a mature sugar maple canopy in Algonquin Park, ON. There was a breeze and random light patches, but there was no sunny spot for portable panels.

The controller was in MPPT and/or ABSORB (14.8V) mode all day, and the ~700W of mono solar never completely charged the ~420Ah of batteries.

By the end of that long day we had harvested 57.7 Ah.

shade can be worse than clouds, and clouds can be bad. As an example, this last week we were at the oregon coast with moderate to heavy cloud layer. My 320W portable panels aimed properly and angled properly were giving me 2.5A with the cloud cover. without the cloud cover I get 20amps in direct good sun with my MPPT controller.

Hi,

What make and type of panels? What charge controller? MPPT or PWM? What type of battery? (flooded, AGM, or LI?)

All of those have effects on shading. I get 17 amps from 256 watts of panels (at solar noon in June, flat, fixed installation)--but only if the battery bank is hungry. My original design included provision to charge one bank while using the other. I've kept that option available.

Searching_Ut wrote:
Shade affects solar a whole lot more than you might expect. To begin with, solar output is much like gas mileage, or horsepower type claims, often somewhat overly optimistic shall we say in the claims. For a flat mounted panel on a good day, figure about 5 amps as a realistic output in good sun, an amp or so more if you tilt it. From here it's all down hill, late in the year, output goes down. A little bit of cloud cover, output drops. Shade on just a portion of your panel, significant power drop. Seeing your output running at only half is fairly common.

Shade of a heavy pine forest often takes my 600 watts of solar from 30 amps down to less than 5. Just for grins I checked my output the other day at Ainsworth state park in the Columbia river gorge, and the output was only 1.7 amps. This was at approximately 2:30pm, light overcast, shade from the canyon wall and heavy forest cover. Solar is great for when it works, but unless you plan your camping around optimizing your solar capture, it's not particularly reliable, or cost effective. On the other hand for me, the simplicity, and quite nature of solar make it worth the installation cost even though it will probably never pay for itself, even though having done all the installation myself it was relatively cheap.

Shade affects solar a whole lot more than you might expect. To begin with, solar output is much like gas mileage, or horsepower type claims, often somewhat overly optimistic shall we say in the claims. For a flat mounted panel on a good day, figure about 5 amps as a realistic output in good sun, an amp or so more if you tilt it. From here it's all down hill, late in the year, output goes down. A little bit of cloud cover, output drops. Shade on just a portion of your panel, significant power drop. Seeing your output running at only half is fairly common.

Shade of a heavy pine forest often takes my 600 watts of solar from 30 amps down to less than 5. Just for grins I checked my output the other day at Ainsworth state park in the Columbia river gorge, and the output was only 1.7 amps. This was at approximately 2:30pm, light overcast, shade from the canyon wall and heavy forest cover. Solar is great for when it works, but unless you plan your camping around optimizing your solar capture, it's not particularly reliable, or cost effective. On the other hand for me, the simplicity, and quite nature of solar make it worth the installation cost even though it will probably never pay for itself, even though having done all the installation myself it was relatively cheap.

You might consider a 100w portable solar suitcase. With 100 feet of cable there will be some loss, but it will still be a useful setup.

I have one of those, and it's worthwhile IMO. I have since added 300w on the roof. That is great in the Southwest. But I still carry the portable.

Because I'm in the middle of some redesign rewiring
I have three panels approx 166w on a separate controller from the other 420w
In full sun I was getting 8+ amps from those panels, they have their own volt amp display, I moved into the shade and it dropped to 640 milliamps, yep less than One amp,
The batteries are at 95 percent charge, the solar voltage drop was too much
At a lower SOC, they charge drop off might not have been as much,
Maybe closer to 2 amps
But you see what were saying

Hi,

I get 7 amps out of a possible 17 amps in leafy shade at solar noon in June.

I get 17 amp-hours total on a clear day on Dec 21.

I assume you meant real "shade" and not clouds but, nonetheless; here are some numbers of what clouds can do to solar collection. It may or may not help... I hope it does! :-)

My Kyocera 51 watt panels output 7 watts each in full shade at latitude 22. Four panels, 28 watts = a bit more than 2.0 amperes for all four panels.

A typical 120WATT solar panel will produce around 6-7AMPS DC current when in High Sun.

It has been my experience to recharge my 50% charged state batteries to their 90% charged state I need to have 14.4VDC with 20AMPs or so of DC current per battery in my battery bank. The batteries will demand alot of DC current at first and then tapper back after 30 minutes of charging and continue to taper back demanding DC current until they reach a charged up state. going from 50% charge to 90% charge in my case takes around three hours of charging. This starts out at 14.4VDC for around an hour then drops back to 13.6VDC for two additional hours and then drops to 13.2VDC until something gets turned on demand DC Current which will then switch to 13.6VDC...

Getting 20AMPS of DC current from solar panels takes several panels in parallel. If you have full high sun all afternoon you can easily reach 90% charge state on a couple of batteries in parallel before you lose full high sun...

I don't have solar yet but planning on getting enough panels on the roof of my POPUP trailer to produce at least 20AMPS of DC Current. Then I plan on running my generator for the first hour to get past the very high DC current demand from the battery bank and when the demand gets down to around 6-8AMPS then shut down the generator and let the panels continue charging the rest of the high sun day.

I think this will work big time for my situation...

You might want to get a couple of portable solar panels that you can move around your camp site to keep in the high sun.

Having a generator insures me I have a recharging source of energy no matter what the conditions are. Adding solar panel for me will just supplements the generator on reaching my daily 50% to 90% charge state on my battery bank.

A downside to my way of camping is I can only do around 12-14 charge cycles of 50% to 90% charge states before losing battery performance and have to do a full 100% charge period which takes 12 hours or so of running my generator. This is usually when we head for the barn so to speak...

Just some things to think about in your planning

Roy Ken