Seeking Solar Panel Geek :)

Stepandwolf

Solar Addict
Here is the deal. Due to size issues, I have focused on a solar panel that meets my needs. As far as how many to buy and how to configure them is another matter. I am building a 24V system with the intent to have a 24V solar array, and battery pack. Am using a Victron 3000va 24/3000/70 Multiplus.

The manufacturer says the panels are 64 cell, but I was told they are really 32 cell. They then said to make them 24v compatible, I should put two in series, and then put the two-panel strings in parallel. Apparently, something about 64 cells is closer to 70 or 72 that is ideal for 24V? I hadn't heard about particular cell configurations being better for one voltage or another.

Originally, using a different BMS, he said I was maxed out at six panels. I don't know if a Victron SCC has such a limitation.

Without a hassle, I can make a string of 6 panels on one side of my TT, and another string of 6 on the other side. Since the AC, etc. are in-between, one set might have shading the other set doesn't have. Doesn't that suggest two SCC is best, one for each side?

1. Would a Victron 100/30 be a good fit for each set of six panels?
2. Would you configure them 2S3P?

Thanks for any ideas or suggestions given I think this is the panel I want!hqst hsp100D-L solar panel.jpg
BTW, I have written HQST/Renogy and haven't heard back.
 

chrisski

Photon Sorcerer
1. Would a Victron 100/30 be a good fit for each set of six panels?
THat would work for what you say. You could also run all 12 into the 100/30. I would expect up to 36 amps from the 100/30 at 24 volts with all panels hooked up. You could run all panels off a 100/50 Which is cheaper Than 2 100/30s.

I have six flat panels on my roof at 12 volts and I can see up to 25 charging amps off those, even thought they’re rated for 36. TO get closer to the 36, I need to angle into the sun. If you want 12 panels at 24 volts, I’d expect you to typically see 25 amps in the winter on a cloudless day.
2. Would you configure them 2S3P?
One of the SCCs I have control six 100 watt panels set up in a 3S2P configuration. I went with that to minimize voltage loss and still deal with 10 gauge wire. I think I set my goal for 3% loss or less, and on my fifth wheel, I could not get that with 10 gauge wire.
maxed out at six panels. I don't know if a Victron SCC has such a limitation.
My Victron 100/30 has no panel number limitation, but depending on the 100/30 Or 100/50, there is a spec about how many amps of panels you can have going in.
 

Hedges

I See Electromagnetic Fields!
Victron 100/30


100V max, 35A Isc max, 30A output. Into 24V that's 720W give or take depending on voltage.
Haven't spotted link to manual or more details, but there will be some minimum PV voltage above battery voltage that's needed.
I'll assume 30V high battery and 5 V headroom, so 35V from panel.

18Vmp from panel x 2 = 36V, but maybe lower on a bad day. Use at least 3 panels
21.6Voc x 4 = 86.4Voc at 25 degrees C.
86.4 x 1.16 = 100.2 (using -15 degrees C and 0.4%/degree C, your location record cold temperature and panel TCR not likely that extreme.)

3 or 4 panels in series is good.
4s2p would be 800W (STC) so a good fit for the charge controller.

12 panels on one 100/30? Could be 4s3p or 3s4p.
If all oriented same direction, about 50% over SCC capability so would clip.
If multiple orientations, might just hit 30A output of SCC.
 

Stepandwolf

Solar Addict
THat would work for what you say. You could also run all 12 into the 100/30. I would expect up to 36 amps from the 100/30 at 24 volts with all panels hooked up. You could run all panels off a 100/50 Which is cheaper Than 2 100/30s.

I have six flat panels on my roof at 12 volts and I can see up to 25 charging amps off those, even thought they’re rated for 36. TO get closer to the 36, I need to angle into the sun. If you want 12 panels at 24 volts, I’d expect you to typically see 25 amps in the winter on a cloudless day.

One of the SCCs I have control six 100 watt panels set up in a 3S2P configuration. I went with that to minimize voltage loss and still deal with 10 gauge wire. I think I set my goal for 3% loss or less, and on my fifth wheel, I could not get that with 10 gauge wire.

My Victron 100/30 has no panel number limitation, but depending on the 100/30 Or 100/50, there is a spec about how many amps of panels you can have going in.
Hi Chris, Since to get 12 panels on my roof, it would mean running a row down both sides of the roof and a 12th one stuck in the middle of the roof behind the AC. Regardless of the TT orientation, other than high noon, the AC, vent fans, etc. will be providing some amount of shading. It was my understanding that even a part of one panel shaded deteriorates the whole string? That is my rationale behind two SCC, one for each side of the roof, so if one side is partially shaded, it won't affect the other six panels on the other SCC. When looking at panels for my house, each panel had it's own controller so that any panel that was shaded had no effect on each other. With one controller per string I thought shading had to be avoided at all costs and having two SCC's would help that.

So there is no inherent panel limitation, just the amperage and voltage limitation of the controller.

Still trying to find out what the number of cells per panel has to do with preferred cell count.

Thanks!
 

Stepandwolf

Solar Addict
Victron 100/30


100V max, 35A Isc max, 30A output. Into 24V that's 720W give or take depending on voltage.
Haven't spotted link to manual or more details, but there will be some minimum PV voltage above battery voltage that's needed.
I'll assume 30V high battery and 5 V headroom, so 35V from panel.

18Vmp from panel x 2 = 36V, but maybe lower on a bad day. Use at least 3 panels
21.6Voc x 4 = 86.4Voc at 25 degrees C.
86.4 x 1.16 = 100.2 (using -15 degrees C and 0.4%/degree C, your location record cold temperature and panel TCR not likely that extreme.)

3 or 4 panels in series is good.
4s2p would be 800W (STC) so a good fit for the charge controller.

12 panels on one 100/30? Could be 4s3p or 3s4p.
If all oriented same direction, about 50% over SCC capability so would clip.
If multiple orientations, might just hit 30A output of SCC.
Hello Hedges, Don't think we have "talked" before.

This is a link to the manual manual

OK, I understand that the string of panels would need a voltage greater than the battery bank. Seems you are saying two of the 12V panels in series (=24) might not have enough voltage based on temp, etc? So you would suggest at least a 3S to keep the voltage over 24V? If I am concerned about shading due to splitting of the panels on each side of the roof, the most I can put on one side is 6 panels. So you think 3S2P would be fine for that?

Since I am still trying to understand the impact of shading, I am still thinking two SCC's might give me more total energy. The factory solar wire is 10GA which was also a reason for going with 24V. Seems the six panels in a 3S2P configuration should work fine with the 10GA wire. I would likely being the install with six panels using factory cable and add on six panels and put in a new cable for that.

Thanks so much!
 

Stepandwolf

Solar Addict
Hello sir,
The first link is something I researched extensively when I was looking at solar for my home. In the case of my TT, my limitation will be space for solar panels, and whatever energy I can get, the better. In other words, I will take what I can get :)

I also have done some research into panel configurations and have the basics down. The article doesn't mention number of cells per panel being a factor which is still my main question on that topic.

The third link regarding how much I need to charge the battery is kind of moot. Same as the previous point, I can only add so many panels so they will do what they can do, and if not enough, I use less, drive to a sunnier spot, or supplement with a gen which I don't have and would like to avoid. I suspect no matter how big my battery banks are, my solar panel limitation will ultimately determine if I can run AC or not.

The last link was the most interesting or beneficial. A lot of the info applies to large land-based solar arrays. With a limited number of panels I have less options. The thing of most interest was the sun blocking and the use of diodes.

The graphics showed diodes connected to the panels and mentions some SCC's have diodes to reduce night time draw. I wasn't sure if it is telling me to add diodes in case of sun blockage, or if the information is for people who typically get sun blockage, like from trees in their yard.

Thanks....
 

chrisski

Photon Sorcerer
It was my understanding that even a part of one panel shaded deteriorates the whole string?
That is true it does effect the string. This is particularly noticeable in the winter months. With the Air conditioner shading my Front set of three panels.

I found to prevent voltage loss with my wire runs and staying at 10 gauge, I needed to go 3S2P.

I located the panels as ideally as I could. The choice I had was whether or not to parallel them and get huge wires or set them up series and deal with thin wire.

I'll say even in the shortest days of the year, from my six 100 watt roof panels, I will get between 20 and 25 amps o charging to my 12 volt battery between 10:30 - 1:30.

I added some portable panels to a second SCC, four 100 watters. These ended up producing more power than my roof panels because of they are angled to and azimuthed towards the sun. I get up to maybe 30 charging amps at peak production, but they start producing power a couple hours before and a couple hours after the roof panels.

My final panels I added to a 3rd SCC for that build was 350 watts of panels flat mounted on the roof. With those panels added, I see up to 45 charging amps. That will take care of my power needs and I no longer needed to set up my portable panels. My typical draw is about 110 ah -120 ah on my 12 volt system overnight, with the most I saw was 165 ah. Most of that is the DC blower motor for the propane heater.

With a blank slate and the good planning you're doing on your part you couls do it with better placed panels to a single SCC. Two SCCs are good to for redundancy.

I found statements like avoid vents and air conditioners are not practical with the space you have on your roof to add these panels and its like a jigsaw puzzle.
 

Stepandwolf

Solar Addict
I wanted to add that I got a response from HQST which made me wonder if I was on the same page with them.

I asked them about a limit of the panels per SCC and the didn't know what SCC was and thought I meant "single circuit regulator" ???

Secondly, I asked about number of panels per "string", and they didn't understand what a string was.

Although I thought I asked simple questions that were easily understood, I will have to wait and see what they say when I further explained my questions.

Regarding the number of cells per panel, and how that factors in, is based on a discussion I had with Dacian back in January. Since he designed his Electrodacus and accessories, I think he has a lot of technical knowledge about solar configurations. I will quote part of what he told me regarding how cell count matters:

"The max power point for a single PV cell is around 0.5V mostly dependent on temperature, a bit lower when the panel is very hot and a bit higher when very cold. So 60 x 0.5V = 30V but PV panels are constant current sources so when connected to battery the voltage will automatically drop to battery voltage usually around 26.5 to 27V most of the time with LiFePO4 with 72 cells the max power point voltage may be around 36V in same temperature conditions so if connected to a 27V battery efficiency will be just around 75 to 80% so you just pay extra for those 12 cells and have a 20% larger panel that will perform the same as the 60 cell panel."

Dacian said that although the panels claim to be 64 cell, they aren't, and are really 32 cell. By putting two in series you get to 64 cells.

None of my reading or videos I have watched discussed matching cell count to voltage output and how that can be used to determine what panels are needed and how to wire them. My interpretation of what he is saying is that for a 24V system, a cell count of 60 is ideal from a matching of voltage to battery. So the two panels with 32 cells each in series would be 64 cells and would only be "wasting" 4 cells, whereas someone installing 72 cell panels into the same battery bank is wasting cells and voltage.

I sure hope that seeing Dacian's explanation will make sense to someone else and if Dacian is correct, as he should be, then why isn't cell count mentioned more?

Thanks for all your help!
 

Stepandwolf

Solar Addict
That is true it does effect the string. This is particularly noticeable in the winter months. With the Air conditioner shading my Front set of three panels.

I found to prevent voltage loss with my wire runs and staying at 10 gauge, I needed to go 3S2P.

I located the panels as ideally as I could. The choice I had was whether or not to parallel them and get huge wires or set them up series and deal with thin wire.

I'll say even in the shortest days of the year, from my six 100 watt roof panels, I will get between 20 and 25 amps o charging to my 12 volt battery between 10:30 - 1:30.

I added some portable panels to a second SCC, four 100 watters. These ended up producing more power than my roof panels because of they are angled to and azimuthed towards the sun. I get up to maybe 30 charging amps at peak production, but they start producing power a couple hours before and a couple hours after the roof panels.

My final panels I added to a 3rd SCC for that build was 350 watts of panels flat mounted on the roof. With those panels added, I see up to 45 charging amps. That will take care of my power needs and I no longer needed to set up my portable panels. My typical draw is about 110 ah -120 ah on my 12 volt system overnight, with the most I saw was 165 ah. Most of that is the DC blower motor for the propane heater.

With a blank slate and the good planning you're doing on your part you couls do it with better placed panels to a single SCC. Two SCCs are good to for redundancy.

I found statements like avoid vents and air conditioners are not practical with the space you have on your roof to add these panels and its like a jigsaw puzzle.
Hello again sir,

Not having boondocked with a solar configuration or even an AC, I am kind of guessing a lot of things regarding intended usage. That leaves me with a couple goals. I want to put the most panels I reasonably can on the roof and I don't want any side mounted panels. Further, I hope my energy needs don't push me into panels stacked up on the ground around the TT. My set of panels should handle all normal power needs including running the fridge on AC so as not to use propane. The single issue is the AC. Will I be able to run it at all, the worse hours of the day, or it just won't be practical to use the AC on solar power at all. I know I might need a soft start kit for the AC. This will all boil down to how much time I will spend chasing 70 vs. being able to stay in a location that gets warmer and "some" AC might be enough.

I still think due to shading that a second SCC might provide more power, not just redundancy. I need to do more research into sun shading or simply go with my instinct and put in a second SCC and set of panels later, i.e. last six panels.

I am attaching a drawing of my roof so you can see how efficiently I placed the panels in the space. I mentioned earlier that I picked the panel I did as the panels are 33" tall so they just fit in my 34" space along the sides of the trailer. The AC is the "fattest" component that limited my space most.

I intend to run 1.5" box aluminum trails at the top and bottom of the panels with a few cross-rails put in, maybe every other truss. By using the railing system, I greatly reduce holes in the roof, i.e. only in trusses. The rail system will make it easier to put in a tilt system later if I wish. The rails also allow me to keep the panels flat despite slight curvature to the roof. I can also place the rails high enough so the panels aren't blocked by sun lights or exhaust vents.

trailer roof4.jpg
 

chrisski

Photon Sorcerer
The single issue is the AC. Will I be able to run it at all, the worse hours of the day, or it just won't be practical to use the AC on solar power at all.
I can't say for sure. I am going to turn my AC on later this year after the 24 volt is done.

There is a user that has a 25' TT hooked up to a VIctron 3000 watt 12 volt muliplus that uses an Easyplus to run AC as much as she wants. She also has a lot of BB batteries eight of them, with more waiting to be installed. Also not sure on the amount of panels, but she claims about 520 watts of AC usage. She said the Easy Plus was needed to spin the AC up without tripping the inverter.


I also found with my propane fridge, it pulled 320 watts when on, so running through the night for me was not an option. Turned out that so little propane was used, it is not as much of a draw as I thought. Nothing close to the propane heater. I run my fridge on electric in the day and propane when the panels aren't producing.

Panels need a little bit of space between them. My Renogy said 1/4". Also need to be able to get to the mounging bolts.For my tilt panels, they require a fists worth so I can get to the tilting mechanism. With several panels on each side, that could add 2' to the width of a panel.

I have only tilted my panels once. In November it got me 40% more power, but there were night time winds that would rock the trailer, and I did not want my panels up in that, so I have not tilted them since.
 

Stepandwolf

Solar Addict
I can't say for sure. I am going to turn my AC on later this year after the 24 volt is done.

There is a user that has a 25' TT hooked up to a VIctron 3000 watt 12 volt muliplus that uses an Easyplus to run AC as much as she wants. She also has a lot of BB batteries eight of them, with more waiting to be installed. Also not sure on the amount of panels, but she claims about 520 watts of AC usage. She said the Easy Plus was needed to spin the AC up without tripping the inverter.


I also found with my propane fridge, it pulled 320 watts when on, so running through the night for me was not an option. Turned out that so little propane was used, it is not as much of a draw as I thought. Nothing close to the propane heater. I run my fridge on electric in the day and propane when the panels aren't producing.

Panels need a little bit of space between them. My Renogy said 1/4". Also need to be able to get to the mounging bolts.For my tilt panels, they require a fists worth so I can get to the tilting mechanism. With several panels on each side, that could add 2' to the width of a panel.

I have only tilted my panels once. In November it got me 40% more power, but there were night time winds that would rock the trailer, and I did not want my panels up in that, so I have not tilted them since.
Maybe I saw something about the same TT user who runs all on solar. I don't know if the battery bank size matters as you are probably going to have the AC running when the sun is shining (or longer) so that means pretty much all solar charging will be needed by the AC while it is on. The ability to run AC "all day" is probably more about solar panels then anything. With a 25' TT, she wouldn't have much more roof than me, i.e. maybe at the most a panel or two more, but if not optimized for the space, she might not have as much panel coverage as my ongoing intent.

I know about the two easy start companies that are in competition with each other. There is also the hard start option allows some people to get by without the easy start cost. Hard start is only a $12 capacitor.

Kind of lost you on the fridge. When on AC it draws 320W constant? I didn't know what my own fridge drew, so I checked. 10W when running in propane mode, i.e. 12V, and 300w 2.5a in AC mode. I suspect during the day when warmer it will run more, and hardly at all over night. My home fridge has a random compressor noise, so I know when it is running, and it seems to only run minutes per hour. Still seems, if you have extra battery, run on AC, it not, then you don't have a choice :)

Didn't think there needed to be a gap between panels. I didn't see such a spec like you do on other things, i.e. the inverter wants 4" sides and top. There is actually plenty of horizontal room. The panels are 26.4" wide. On the driver side, I have 144 inches, 5 panels is 132". On the passenger side, I have 172" and 6 panels would be 158.4". So on both sides, I have about a foot to play with...either leaving room on the ends or space between.

I only need enough space under the rail for a wrench but will have more room then that. I will put the bolts in frame of the panel, lower into place, and add washers and nuts on the underside of the rail. On the outward side, I am guessing the roof slope will give me another inch or so.

I will be comparing some tilt options to see how much vertical space is needed. I saw one design where they basically only needed as much space as the width of the motor, just a few inches. I don't think a tilt mechanism is in my near term future as there is so much else to do first.

Surprised that the surface area of the panels would create as much wind surface to even count compared to the square footage of the side of the RV facing the wind?

Reminds me of when I was sailing in Lake Superior with a buddy. My friend's sailboat was designed to be sailed so the ratio of exposed hull compared to the sails was quite high. He pointed at a nearby "sailboat" that was so tall, and had such small (comparative) sails that you could see that when tipping over a bit, the hull had more exposed surface area than did the sails.

Thanks again Chris!
 

chrisski

Photon Sorcerer
Surprised that the surface area of the panels would create as much wind surface to even count compared to the square footage of the side of the RV facing the wind?
Some nights the trailer would rock because of the winds. THey came out of nowhere. Calm until sunset, and then gradually going up. Most nights they were at 15 knots, but some nights a nearby weatherstation locked them at gusts to 35 knots.

I think its because the places I stay in the winter were at the edge of mountains and a valley. One place was sunset winds. A separate place had the winds shortly before sunrise.
 

Stepandwolf

Solar Addict
Some nights the trailer would rock because of the winds. THey came out of nowhere. Calm until sunset, and then gradually going up. Most nights they were at 15 knots, but some nights a nearby weatherstation locked them at gusts to 35 knots.

I think its because the places I stay in the winter were at the edge of mountains and a valley. One place was sunset winds. A separate place had the winds shortly before sunrise.
Guessing that wasn't with levelers? The best RV is going to react to weather more than a house. With that kind of wind, I would want my panels in other than the most secure position :)
 

Hedges

I See Electromagnetic Fields!
If you wire twelve panels 3s4p or 4s3p and one panel is shaded, will probably produce same as 3s3p or 4s2p, respectively.
Most SCC only observe slope of the hill where they are standing, won't cross a valley to reach a higher mountain. Some do, however.

Panels typically have 2 bypass diodes, some larger panels have 3. If shade moves onto just the 50% of panel bypassed with a diode, you might get 2.5s4p or 3.5s3p, if the power/voltage curve of the panels makes that a monotonic ramp up. As shadow moves covering second half, maybe you get 2s4p or 3s3p. Well, maybe not 2s4p because 3s3p would be higher. But maybe 3s3p not 4s2p.

I had a setup with 9s2p, and shading one panel appeared to give output of about 17 panels. With only one panel out of 9 in series shaded, it was still operating near Vmp. Shorter string, larger shift off Vmp.

If part of the day has that panel unshaded, will probably work well either way.

Victron shunt communication - I don't find the diagrams now. What I saw had a separate box that measured shunt and communicated to SCC. I don't know if the Smart Shunt also does that; you'll have to read up on them. Look for a data cable going to SCC.
 

Stepandwolf

Solar Addict
The shunt manual is here.

I don't know what the shunt does more than show state of charge and flow in either direction. I don't think there is any interaction with the controller. The shunt only connects to the battery. It connects via Bluetooth to an app, but only for informational purposes.

So, it seems partial shading isn't as degrading as I thought, but it still seems to charge controllers makes things even better?
 

Hedges

I See Electromagnetic Fields!
"two charge controllers"?
Get your grammar and spelling straight, or I'll make fun of you. Just like the other kids did when I was growing up, saying, "You look the the guy from Mad magazine!"

Two charge controllers may harvest more power, if you dedicate one to a PV string that gets one panel shaded sometimes.
Two is good for redundancy, if one fails you still have one.
I like to parallel two strings of different orientations on one SCC (or GT inverter in my case.) It is about 2% lower yielding than separate SCC keeping each string at Vmp, but it lets you fully use an array as much as 40% oversize (if 90 degree angle between strings, area presented to sun is 0.7 times what all same orientation would be.)

You may want some portable panels. Better angle in winter, or better sun exposure when you can park in shade.
 

Stepandwolf

Solar Addict
"two charge controllers"?
Get your grammar and spelling straight, or I'll make fun of you. Just like the other kids did when I was growing up, saying, "You look the the guy from Mad magazine!"

Two charge controllers may harvest more power, if you dedicate one to a PV string that gets one panel shaded sometimes.
Two is good for redundancy, if one fails you still have one.
I like to parallel two strings of different orientations on one SCC (or GT inverter in my case.) It is about 2% lower yielding than separate SCC keeping each string at Vmp, but it lets you fully use an array as much as 40% oversize (if 90 degree angle between strings, area presented to sun is 0.7 times what all same orientation would be.)

You may want some portable panels. Better angle in winter, or better sun exposure when you can park in shade.
Please tell me what my spelling and grammar error was so I can learn instead of just telling me I am grammatically challenged. I use the Mad magazine, i.e. Alfred E Neuman avatar as we share a philosophy. "What, Me Worry".

Because it is a mobile situation, and even if I sit in one spot, the sun will move and one set of panels will have partial shade, even if not under a tree or some other obstacle.

For optimization of my footage, all panels will share a common orientation, only being which ones are blocked my stuff on the center of the roof.

I might reconsider portable panels if I find the need. I should qualify my needs by stating it isn't my intent to stay for extended periods of time in one spot. It is my intent to move around and I will add alternator charging at some point to help keep the batteries topped off.

To fill my desire to do landscape and 360 photography means I will be moving to new photographic opportunities.

I am trying to decide to just install six panels now as that is all in one row, or go with the full 12 panels, with two rows plus an odd one out. I am also trying to decide about bumping my battery bank from eight 272A cells in an 8S to sixteen cells in that some Lishens just became available.

Thanks!!
 

Boondock Saint

Solar Addict
I admit this is my first viewing of this thread.

I see your size constraints. I don't like playing solar tetris any more than you do, but I encourage you to look at fewer panels to fill that space running lengthwise. I've seen a few narrow longer ones used in marine applications. Larger panels can have 3 diodes with the benefit as mentioned. If you can "place the rails high enough so the panels aren't blocked by sun lights or exhaust vents" it might be that you really have more options for larger panels. Yes Max Fans raise and you need some clearance, but if they are covered with a panel, you don't need that additional shroud over them.

Based on the response from HQST I would purposefully never "be on the same page with them". Just my 2 cents.

Depending on which Victron pieces you buy, you don't need the Smart Shunt.

"So, it seems partial shading isn't as degrading as I thought, but it still seems to charge controllers makes things even better?" The difference between "to" and "two" is a single keystroke, it doesn't mean you don't know the difference or are illiterate. I do a lot worse when I get liquored up and post here.

As mentioned with two SCC you have some redundancy and optimization. You should do it, stuff happens. If you go with all Victron products the equipment pieces will talk amongst themselves and you'll have a better end to end system than with disparate parts. This will probably be more expensive. When I looked at warranties, service in case of RMA and reliability etc, I was sold on using a Victron AIO system. I couldn't come to that conclusion with any other brand. Again just my 2 cents.

It seems $6k for parts doesn't go as far as it used to.


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Hedges

I See Electromagnetic Fields!
Please tell me what my spelling and grammar error was so I can learn instead of just telling me I am grammatically challenged. I use the Mad magazine, i.e. Alfred E Neuman avatar as we share a philosophy. "What, Me Worry".

I asked "two charge controllers"? to see if you meant that rather than the "to charge controllers" you said, which I couldn't make sense of.
I find I make a lot of typos like that these days. Phonetically identical words that are spelled quite differently, and other substitutions.
I like to throw stones from my glass house :)

I would want the double quantity of panels. That will produce more, make up for bad days or heavier usage.

We generally recommend larger panels, used or overstock, because the price point is better. What matters for mobile is how many watts you can fit. Are those panels around 20% efficient (200W/m^2)? My older ones are close to 13%, so higher efficiency panels make 50% more in the same space.
 
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