800W solar install

[757driver]

Originally Posted by Ivylog

Having hauled a spare tire for many miles around a roof vent in the middle of the roof without fastening it down, I'm going to try it without holding them down. I have added a 2"X 8" triangle in front of the first panel to keep air out although that far forward it's probably in a low pressure area...no lift and protected from the 70 mph winds.

There is also a 1" opening at the top and bottom of the panels so doubt there is enough pressure under the panels to lift them up. I may mount my GoPro up there and get it up to speed+ and record what happens.

I may run a cord from the 2x8 triangle up front through the grey tank vent and over the rear panel to keep them from raising up too much. Put some small pieces of paper under the bottom of the supports and if they do not blow out from under...no problem and no cord needed.

They may now lift in the wind while driving but what about bouncing? Don’t want one to come banging down on the roof and break.

[geordi]

There is a MUCH different profile in the wind than a tire, although I'm rather distressed that you drove any major distance with something so heavy unsecured on your roof.

Bernoulli's air pressure principles (and how airplanes fly) is that the low pressure area you think exists under the panels actually is a HIGH pressure area - Not from wind pressure, but because the wind above the panels is moving faster, that has less pressure and the lower speed air has MORE pressure. The panels WILL likely lift up. Please secure them.

I was going to suggest a different controller for your setup, but I'm rather curious about the panels you selected. I recently finished a 1020 watt array with 3 350 watt panels, that only output 44 volts each nominal. I'm surprised that there are 80 volt panels in such a low wattage. As long as the voltage numbers match up however, you are fine within a quality controller, they can self-limit. Also if you don't have enough battery capacity, you will actually max out the charge rate very quickly and the array will be prevented from producing more to protect the batteries. I discovered this b/c my controller is only in "bulk" mode for about 2 hours, and even with other uses during the day it limits to about 4KW produced per day.

[Ivylog]

You all must have some really rough riding MHs...mine does not bounce down the road and it does not go negative Gs...what would be necessary for the tire to lift up the 8” to clear the Max vent or for the panels to bounce up/down.

I have 4 L16 batteries...800AH so I should be OK with 700+W of solar.

I needed 2’ X 4’ size panels (100W) to fit along the drivers side of the MH. I realize these are not your normal individual cell panels, they are thin film. Here are the specks:
First Solar series 4 thin film solar panels:
NOMINAL VALUES FS-4110-3
Nominal Power6
(-0/+5W) PMPP (W).......... 110.0
Voltage at PMAX VMPP (V).... 67.8
Current at PMAX IMPP (A).... 1.62
Open Circuit Voltage VOC (V) 86.4
Short Circuit Current ISC (A)1.82
Module Efficiency % ........16.7

[CountryFit]

Never underestimate the power of wind; especially you are in FL you know it. Sometimes a small tree branch could rip of panels. There is a nice guy in this forum called "Reed Cundiff" whose panels once were ripped off by trees. My front panel anchor screws were lifted and turned by 1/4 turns, prompted me to install a custom air dam. Here if you want to read.

Anyway, people learned hard lessons and here to share. Certainly everyone has his/her own opinion. Just remember better safe than sorry.

[Ivylog]

Thanks everyone for your concerns and advice but (don’t you love it when BUT is added)??? Having installed your normal solar panels on your normal MH roof they were well fastened down and did not tilt.

Everything about this installation is not normal an unlike about everything else, there is not a Utube video on how to install. With the raised rails (10” high) alone each side shading of the panels was a real concern BUT created an opportunity to tilt them. With all the things in the middle of the roof I needed 2’X4’ (100W size) panels to go along the drivers side of the roof.

By now you know the panels I bought are not your normal solar panels (about like me some say) BUT what do they know? No alum frame and a thin film sandwiched between two plates of glass making for a very heavy panel and 80V. Should have weighed them but probably 30 lbs each. These panels are usually only available for larger solar farm projects...not the retail market.

I looked at recent wind tunnel test on 18 wheelers BUT I already had a fair understanding of the aerodynamic of a brick... low pressure area at the front of the roof and turbulent air coming back down at the rear. Between how well protected and how heavy these panels are I’m confident my test pieces of paper will still be there after a high speed test run, BUT you never know.

[Reed Cundiff]

Originally Posted by CountryFit

Never underestimate the power of wind; especially you are in FL you know it. Sometimes a small tree branch could rip of panels. There is a nice guy in this forum called "Reed Cundiff" whose panels once were ripped off by trees. My front panel anchor screws were lifted and turned by 1/4 turns, prompted me to install a custom air dam. Here if you want to read.

Anyway, people learned hard lessons and here to share. Certainly everyone has his/her own opinion. Just remember better safe than sorry.

One panel ripped loose on fifth wheel between Tulum and Merida in Yucatan. Then had 315 W panel on 19’ Roadtrek ripped off by the world famous winds in Isthmus iof Tehuantapec. Church’s Guide to RVing in Mexico mentions these winds. The thin webbing on panels is not designed for these forces and normal aluminum mount fittings fatigue. The fittings should be examined routinely. We have changed to 2” extruded aluminum L railing (son in solar business has a lot of this as scrap). We put 1” x 1/4” stripping on the panel webbing as an extended “washer” to prevent ripping loose from panel

Reed and Elaine

[geordi]

Originally Posted by Reed Cundiff

One panel ripped loose on fifth wheel between Tulum and Merida in Yucatan. Then had 315 W panel on 19’ Roadtrek ripped off by the world famous winds in Isthmus iof Tehuantapec. Church’s Guide to RVing in Mexico mentions these winds. The thin webbing on panels is not designed for these forces and normal aluminum mount fittings fatigue. The fittings should be examined routinely. We have changed to 2” extruded aluminum L railing (son in solar business has a lot of this as scrap). We put 1” x 1/4” stripping on the panel webbing as an extended “washer” to prevent ripping loose from panel

Reed and Elaine

I have my 350 watt panels attached flat to the roof with these wide plastic "feet" that I found on Amazon, drilled and screwed directly into the aluminum sides of the panels, and self-tapping screws (lots of them) with lots of silicone sealer under the feet gluing them directly to the roof. The panels span my roof from side to side almost as wide as the coach is (40x80 panels) and two of them are in front of the bedroom AC and roughly at the middle of the coach among all the other roof furniture, the third is behind the rear AC unit. There's barely a couple inches of clearance under the panels to the roof, so I'm not really worried about the wind being able to even try getting under them and getting any grip - But then I'm also familiar with using the silicone sealer as glue, I covered my vents with those Maxxair covers, and didn't use any screws on the install - just layed a bead of silicone on them and placed them. Works great, unbelievably strong and keeps the bugs out.

[vsheetz]

Why all in parallel? Create multiple strings and use a MPPT controller maximize production. Check out the Midnight Solar Classic series of controllers. Various voltage handling versions available.

[Ivylog]

Originally Posted by vsheetz

Why all in parallel? Create multiple strings and use a MPPT controller maximize production. Check out the Midnight Solar Classic series of controllers. Various voltage handling versions available.

Guess you missed they are 86V panels and 7 panels.

[vsheetz]

Originally Posted by Ivylog

Guess you missed they are 86V panels and 7 panels.

Multiple strings, not one. Plus my comment regarding controller voltage.

[geordi]

Originally Posted by vsheetz

Multiple strings, not one. Plus my comment regarding controller voltage.

Victron has some great controllers too, but the number of panels he has, he'd need a 1000 volt controller to have more than 2 of them together - Even then, you can get 100 or 150 volt controllers, but they tend to jump in price and complexity up to 1kv or 1500v pretty fast and that requires special wiring too. 600 volts is the limit of most shielding until you start getting special.

I have my panels in series and it works perfectly b/c I have a 150 volt controller and I'm just below the capability of the controller with my panels. His panels would have to be in parallel with my controller (which would work fine) OR the controller would need to be upsized to handle higher voltage.

An MPPT is constantly adjusting the ratio between amp and voltage anyway - as long as the source voltage is at least about 30% higher than the delivery voltage, there is no significant advantage to going higher in the voltage with the delivery length of the cables in this application. He's not losing any power by being at 80v parallel into his controller, just as I'm not losing any at 140v serial into mine. The cable lengths are maybe 30 feet at HV. It is the heavy low voltage cable that may have losses - I put my Victron in the battery bay so it is super close to the delivery point, my 4/0 welding wire cables are only about 4 feet long!

The difference is he has 7 100w panels at 80vdc, I have 3 350w panels at 45vdc. I'd need heavier cable if I was trying to stuff that much down to the controller in parallel, but at ~140vdc, that 10 gauge wire is more than adequate. I used 12 gauge as interconnects between the panels b/c I had it laying around, and that would also have been OK as the feed to the controller. 12 gauge is easily able to handle 2500 watts at 120v, 1kw is simple stuff.

[vsheetz]

Originally Posted by geordi

Victron has some great controllers too, but the number of panels he has, he'd need a 1000 volt controller to have more than 2 of them together - Even then, you can get 100 or 150 volt controllers, but they tend to jump in price and complexity up to 1kv or 1500v pretty fast and that requires special wiring too. 600 volts is the limit of most shielding until you start getting special.

I have my panels in series and it works perfectly b/c I have a 150 volt controller and I'm just below the capability of the controller with my panels. His panels would have to be in parallel with my controller (which would work fine) OR the controller would need to be upsized to handle higher voltage.

An MPPT is constantly adjusting the ratio between amp and voltage anyway - as long as the source voltage is at least about 30% higher than the delivery voltage, there is no significant advantage to going higher in the voltage with the delivery length of the cables in this application. He's not losing any power by being at 80v parallel into his controller, just as I'm not losing any at 140v serial into mine. The cable lengths are maybe 30 feet at HV. It is the heavy low voltage cable that may have losses - I put my Victron in the battery bay so it is super close to the delivery point, my 4/0 welding wire cables are only about 4 feet long!

The difference is he has 7 100w panels at 80vdc, I have 3 350w panels at 45vdc. I'd need heavier cable if I was trying to stuff that much down to the controller in parallel, but at ~140vdc, that 10 gauge wire is more than adequate. I used 12 gauge as interconnects between the panels b/c I had it laying around, and that would also have been OK as the feed to the controller. 12 gauge is easily able to handle 2500 watts at 120v, 1kw is simple stuff.

I agree that having all seven in parallel is likely the way for the OP to go.

Why a 1000v controller needed for a string of three 80v panels?

Thanks for the primer on mppt and such. I currently have three 500w / 100v strings each using #10 wire to a Midnight Solar combiner box / breaker panel. then on to a Midnight Solar 150 controller. Combiner box and controller co-located near the batteries. Plus a fourth 200w string made portable that can be plugged into the combiner box.

[geordi]

Originally Posted by vsheetz

I agree that having all seven in parallel is likely the way for the OP to go.

Why a 1000v controller needed for a string of three 80v panels?

Thanks for the primer on mppt and such. I currently have three 500w / 100v strings each using #10 wire to a Midnight Solar combiner box / breaker panel. then on to a Midnight Solar 150 controller. Combiner box and controller co-located near the batteries. Plus a fourth 200w string made portable that can be plugged into the combiner box.

I was thinking about the 1kv controller if all the panels were linked in series. His situation is probably best suited for everything in parallel b/c of the already high panel voltage, and since they match they can all be connected in any way that is convenient - EXCEPT the odd numbered panel. If each string is 2 panels (160v / 1.25amp) and 3 strings in parallel (160v / 3.75 amps) to the controller) that works. But connecting that lone panel in parallel to the others... bad idea. It will drag down all the rest of the strings to 80v, cutting them by half. The current will still be the same, but b/c of the relationship between voltage and amperage, the wattage of the mismatched array would not be 700 watts... But 400!!!

Now your situation: You said you have 3 500w strings and one 200w string. You didn't say what the voltages are, so I don't have enough information to draw any conclusions but here are some possible configurations:

Panels are all 24 volts / 100 watts - 500w strings in series = 5 panels, 120v, 4a per string.
Link in parallel, 120v, 12a, 1440w for the array.
NOW... Add an additional 200 watts portable. What's the voltage? If they are the same 24v panels... 2 panels in series, 48v, 200 watt. Add to the larger array in parallel... Total array is now 48v, 16a, 768watt.

Mismatching panels is just never a great idea. I'm curious of your setup, what are the voltages and panel ratings? I'm curious if there is a way to add those extra 200 watts without losing half the array's potential - not sure there is.

[vsheetz]

Originally Posted by geordi

I was thinking about the 1kv controller if all the panels were linked in series. His situation is probably best suited for everything in parallel b/c of the already high panel voltage, and since they match they can all be connected in any way that is convenient - EXCEPT the odd numbered panel. If each string is 2 panels (160v / 1.25amp) and 3 strings in parallel (160v / 3.75 amps) to the controller) that works. But connecting that lone panel in parallel to the others... bad idea. It will drag down all the rest of the strings to 80v, cutting them by half. The current will still be the same, but b/c of the relationship between voltage and amperage, the wattage of the mismatched array would not be 700 watts... But 400!!!

Now your situation: You said you have 3 500w strings and one 200w string. You didn't say what the voltages are, so I don't have enough information to draw any conclusions but here are some possible configurations:

Panels are all 24 volts / 100 watts - 500w strings in series = 5 panels, 120v, 4a per string.
Link in parallel, 120v, 12a, 1440w for the array.
NOW... Add an additional 200 watts portable. What's the voltage? If they are the same 24v panels... 2 panels in series, 48v, 200 watt. Add to the larger array in parallel... Total array is now 48v, 16a, 768watt.

Mismatching panels is just never a great idea. I'm curious of your setup, what are the voltages and panel ratings? I'm curious if there is a way to add those extra 200 watts without losing half the array's potential - not sure there is.

The portable setup is used only when the rooftop panels are blocked.