Adding to roof rack solar / revamping

hour

Observer
Hi all..

I currently have 2 x 100w Renogy Compact solar panels on my roof rack that clock in around 40x40" side by side. This is an improvement over my previous setup which used the non-compact versions, which occupied a 40x47" footprint. I was pretty thrilled to reclaim 7 inches of rack space while keeping the power output the same. I bought 3 of the compact panels but due to mounting challenges (supports running front to back instead of side to side like I currently have), the third panel remains unused in my garage.

I'm not opposed to replacing the whole thing with a single large panel but the standard dimensions kind of suck. Example: I can get a 270w-350w+ panel that's 39x66". For people like me who are more concerned over dimensions and power output over price, there's really no point to get a 270w. But... 65" would eat up my entire roof rack. At that point I'd be best to just remove the megawarrior basket but my fancy low profile mounting solution using carriage bolts had the consequence of making some bolts impossible to remove. It's a permanent fixture on the shell.

I've been drawn to panasonic HIT panels because they seem to be defying these standard dimensions (340w in a 41.5 x 62.5 footprint) which is great, since I do have a hair over 42" width to play with. But alas, they're still 62" long - most of the basket would be consumed and 340w is more than I need. The unicorn would be finding something 39-42" wide x (as short as possible) producing over 240w. But yeah, standard dimensions conundrum - and difficulty searching for panels by dimensions. I've opened about a million PDF spec sheets at this point and converted mm to inches, gotten skunked, rinse/repeat.

solarside.jpg

IMG_3004.jpg

If anyone has any leads on ways to search by panel dimensions I'm all ears.

I'd be game for putting the third, unused, 100w compact panel I have on drawer slides that tuck beneath the existing panels (that's mostly dead space anyway) but I'm in love with series connections and their benefits. I'd hate to go back to parallel to sidestep shading issues.

draweridea.jpg

The current vacancy in the rear of the rack is awesome the couple of weeks a year that I load it up (mostly plano 42" tactical rifle cases, perfect fit width-wise) so it's unfortunate to reserve that space for 300+ days a year when it's not needed, but removing the third panel (if in a non-sliding configuration) for those trips would be a pain. Plus, if the rear of the rack is loaded I'm almost certainly camping and needing the additional panel even more. The third-panel-on-drawer-slides solution would allow me to get to camp and unload->pull panel out... but not wanting to go back to parallel wiring is big oof. Adding another charge controller could solve this, but my bed setup is already screwy due to a bed slide with battery on it. Two PV wires playing accordion to not get pinched by bed slide already sucks, four would be worse. Mounting the battery in a static location is unfortunately a pipe dream.
 

jonyjoe101

Adventurer
Larger panels would be great in the winter and also cloudy areas. I got a LG 365 watt 39x77 to replace my sharp 240 watt 39x64. I seen up to 17 amps charging power in january (max the the 240 put out was about 10 amps).

In your situation I would figure a way to install that 3rd panel on there. You can never have too many panels. Definitely hook them up in series if your controller can handle the max total voltage, you get max amps from an mppt controller.

In my situation I was going by width, I wanted to use my existing L-brackets, and just put the new panel in, that why I chose the LG panel and also I bought it for 250 dollars. But looking at the measurements on the spec sheets is alot different then when you see the panel up close. The LG panel was a beast, I barely got it to fit in my van to drive it home. I needed the larger panel because the smaller panel wasn't getting my 220ah lifepo4 and 312ah li-ion battery banks charged during winter, both banks were limping along at 30 percent for 2 months, once I got the 365 watt panel both banks were at 100 percent in a little over 1 week.

I wrote down some of the sizes of panels while doing my research from specs sheets, I don't know how accurate it is because solar panels are always being upgraded.
sharp
240 watt
L= 64.6
W= 39.1

lg 365
L= 77.16
w= 39.37

lg 360
L= 66.38
W= 40

405 watt
L= 79.68
w= 40.31

LG SOLAR PANELS 350 WATT
L= 64.25
W= 38.82

435 watt panel
L= 81.4
W= 41.2

355 watt
L= 77
W= 39

lg 340 watt
L= 64.25
W= 38.82

QCELL 305 watt
L= 66
W= 40

hanwha 340
L= 68.5
W= 40.6

hanwa 325
L= 66.3
W= 39.4

picture of my 240 watt with the 365 watt side to side
1 240 365 panels.jpg
 

llamalander

Well-known member
You look like you have plenty of room on the cab, why not figure out how to get the panels on the roof there?
Using the old-style Yakama tracks, I've salvaged the feet from the towers and used those alone to give me a mount that is about an inch above my roof.
In my case I wanted a low-profile mount for my basket on the cab (which is attached to the feet with metal hose clamps) and I put a 310w. panel on the shell, which takes up the whole roof of that.
The basket is pretty easy to get to with any of the doors open and if I pack it right, everything is basically level with the panel.
 

hour

Observer
In your situation I would figure a way to install that 3rd panel on there. You can never have too many panels. Definitely hook them up in series if your controller can handle the max total voltage, you get max amps from an mppt controller.

Definitely can handle that, the current charge controller is a Victron 75|15 SmartSolar. While I wouldn't be taking in any more than 210 watts with this MPPT, the increased footprint and voltage boost going from two to three in series would help. Especially in winter as you said. There was a very noticeable difference going from 2P to 2S. Charging at the ass crack of dawn and helps a lot when angles aren't great - a reality for my flat mounted panels. Way more trouble than it's worth to figure out a tilting system for anything more than one beastly panel, the unicorn I'm seeking. Probably still too much trouble. I also have a Victron 100|30 SmartSolar just sitting in the box, so I could make use of that with a 5 minute switch out. The primary objective was just to increase collection potential.

Your panel size notes were useful and speak to what I was saying about the form factor not necessarily correlating with output. It is interesting that there are so many minor deviations from the 39x66 standard... or loose standard.

a form “C” switch

Thank you, I wasn't aware of such a thing even though it makes sense after a very quick google brush up. I was trying to think of a quick disconnect to incorporate or drop the third panel as needed and nothing made sense in my head. Hopefully I can find some youtube videos of people doing this now that I can incorporate form C in to my search queries.

You look like you have plenty of room on the cab, why not figure out how to get the panels on the roof there?
Using the old-style Yakama tracks, I've salvaged the feet from the towers and used those alone to give me a mount that is about an inch above my roof.
In my case I wanted a low-profile mount for my basket on the cab (which is attached to the feet with metal hose clamps) and I put a 310w. panel on the shell, which takes up the whole roof of that.
The basket is pretty easy to get to with any of the doors open and if I pack it right, everything is basically level with the panel.

Thought about it, added things to my shopping cart, and ultimately bailed. Probably no less than 5 times in 2 years. Obviously dig the low profile thing but haven't been too thrilled about the thought of dropping the headliner and drilling through the roof... many times. I installed the tracks on this camper shell and the 3 before it. Disliked it every time and those were rather low risk endeavors compared to the aluminum roof of my truck. Interesting idea on using the lower parts of towers alone - I've never been a fan of the typical 4+" height of these things. I was actually looking at Prinsu racks yesterday but they omitted the width of the F150 racks on their spec sheet so the day dreaming ended. Wouldn't mind paying for that kind of thing to be professionally installed through the roof.

Thanks guys, I'll keep toying with this in my head and reading. The form C switch to allow third panel as a drawer has a lot of potential though if I can stumble upon some examples. I did find a glimmer of hope for the perfect single panel yesterday on a clown company's website - newpowa. Nothing I could use but they've produced an odd shaped 100w.. so yeah, there's hope of maybe some day finding a 42x52" 260w panel, or something in that ballpark size and wattage wise.
 

llamalander

Well-known member
I did pay a local cap supplier to put the rails on my cab, and it was totally worth it--no leaks, no hassle, 2 or 3 years now of not having to think about it.
With those in place, making your own Prinsu style bar-&-flat rack is probably worth your time, you can mount that straight to the track and skip the towers all together.
Basically a threaded bar that can drop into the slot pointing north/south rotates as you tighten the connecting screw and the bar locks under the rail flanges. A little Locktite will keep it there for years.
 

llamalander

Well-known member
2nd thought;
clamp on some strut to your rack and float the panels over the cab, maybe with a 2 feet on the front to support.
You can fit your 3 panels on front to back and still use most of your rack. I doubt the bed/body flex would be enough to damage the installation.
 

Alloy

Well-known member
Lots of people use VHB tape to install panels on RVs. An air dam across the front will reduce the uplift.

Another option is finding a used roof rack for the cab that a panel(s) can be mounted on

Portable is another option.
 

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