Solar in the shade

[waynefi]

I mostly camp in wooded sites. Am I right in thinking that solar doesn't do much good in that case? My impression is that if part of the panel is shaded, the output of the whole panel drops pretty fast.

My driveway where I store the trailer is also very shaded, so I don't think it would help keeping the battery charged in storage, and of course it doesn't work with snow on the roof, so it's not reliable for keeping charged in winter storage.

[ken_white]

marcsbigfoot20b27 wrote:
If you have multiple 12v panels in parallel, they are actually 18-19 volts or so. Your non MPPT controller sets it at about 14 v to the batt at however many amps from panel size.

Shade just one panel and your voltage can drop to ~10 volts and you get almost no amps from the charger.

Now wire the panels in series and have ~60 volts or whatever your MTTP charge controller can handle......one panel is shaded and you end up with maybe 30 volts, but you are still over 14v which means you still get amps from a MPPT, in a nut shell.

Solar panels in parallel assume the same voltage and have their currents add.

So, if one gets completely shaded (0 amps) and the other two have full sun (max amps), then the current to the controller will be 2/3 of maximum current and at the same voltage as before - this assumes the panels have blocking diodes.

If the panels are in series and one panel is completely shaded, and if the panels have bypass diodes, then the current will stay the same, but the voltage will be diminished by 2/3's.

The series configuration becomes much more of an issue when bypass diodes are not used which effectively limits the current to an almost zero value.

[marcsbigfoot20b]

If you have multiple 12v panels in parallel, they are actually 18-19 volts or so. Your non MPPT controller sets it at about 14 v to the batt at however many amps from panel size.

Shade just one panel and your voltage can drop to ~10 volts and you get almost no amps from the charger.

Now wire the panels in series and have ~60 volts or whatever your MTTP charge controller can handle......one panel is shaded and you end up with maybe 30 volts, but you are still over 14v which means you still get amps from a MPPT, in a nut shell.

[TucsonJim]

waynefi wrote:

TucsonJim wrote:
I set up a portable solar system on mine with 50 feet of cable. I can move the panel to a sunny spot when the roof is shaded.

Do you find a place within 50 ft that has sun most of the day, or do you move the panel during the day chasing the sunny patches?

Many places I camp wouldn't have any spot within 50 ft that has full day sun, and I'm often away from camp during the day.

I only found one campsite last summer in Pennsylvania where the tree canopy was so dense that we couldn't get any sunlight. We also couldn't get a satellite signal. We moved to another camping spot the following day.

[ken_white]

JiminDenver wrote:
A means of back up charging is always a prudent thing when using solar...

X2

[JiminDenver]

A means of back up charging is always a prudent thing when using solar. We may have not needed the generator since going solar but we have one just in case. we even replaced it this year with a newer upgraded model so it like the last one can sit while camping and be exercised once a month at home. Even when we leave it home a pair of heavy jumper cables and the truck act as emergency back up.

[jauguston]

I don't believe that solar only is a viable system for the typical RV'er yet and may never be if they camp in non-serviced sites. The tradeoffs you have to make are not acceptable to most folks. A small generator similar to my Honda EU1000 will replenish batteries when the solar system sits there doing nearly nothing. A combination of generator then solar is great but solar only not so much.

Jim

[pianotuna]

Hi,

Try 100 watt $179.00. I do not know the shipping cost, which can be tres expensive.

phemens wrote:
Pianotuna, any suggestions on the better deals, especially for Canada? I'll be looking to supplement the existing 290 watts I have on the roof, adding a portable 100 watts seems like the way to go for me!

[waynefi]

TucsonJim wrote:
I set up a portable solar system on mine with 50 feet of cable. I can move the panel to a sunny spot when the roof is shaded.

Do you find a place within 50 ft that has sun most of the day, or do you move the panel during the day chasing the sunny patches?

Many places I camp wouldn't have any spot within 50 ft that has full day sun, and I'm often away from camp during the day.

[phemens]

Pianotuna, any suggestions on the better deals, especially for Canada? I'll be looking to supplement the existing 290 watts I have on the roof, adding a portable 100 watts seems like the way to go for me!

[pianotuna]

Hi,

There are much better deals than the itechworld kit.

[xyznotes]

We remote a 160W system from iTechworld, truthfully even in tree canopy we get a very good charge rate. Here is a link:

http://itechworld.com/collections/solar/products/folding-solar-panel-kit-160-watt

[Heap64]

Also keep in mind your camping style as well. We like the trees so we don't get the best performance due to the sites we typically camp at. We would be in trouble if we stayed like that a week or weeks at a time. But we normally don't stay in one spot for more than 4 days.

The solar on the roof sitting in pretty shady spots didn't keep up with our needs everyday, but when we were on the move it did a great job of bring our batteries back up to full or nearly full.

I now know more what to expect. If we are going to camp too long in one spot I will probably seek out a little less shade, but I doubt we will need full sun ever due to our pretty low power needs. If that would ever change I might try a portable panel or two down the road.

[loggenrock]

Being based in the Northeast shade is the rule, not the exception. I, too, opted for a portable set-up - 100W "suitcase" from Renogy. I've got about 25' of cable from the panel to the rig, so I get pretty good range to move it around to harvest photons. ST

[JiminDenver]

Solar has it's place and it isn't in the shade. You would have to be pretty conservative to even have a larger array of the right type of panel cover your needs.