Panel Weight and max size for a trailer roof

I’d like to install an off grid system on the roof of my RV towed trailer. flat roof size 30’ L x 8’ W. Hence, maximum performance/panel, monocrys. maximum size, 60"+ L x 32"W dimension, and lowest possible weight. No manufacturer lists weights, on an RV off grid install this is critical. Also largest SIZE is preferred, again, limiting panel number and minimum fixed points. With this max roof covered surface installation, obviously with 1 or 2 inverters, (Sol ARK hybrids?) I’d like a substantial # of Lithion battery pack(s) added below. Can battery pack products offered here in US such as SunRun and Tesla Powerwall, usually mounted on the wall vertically, can they be installed flat / horizontal with adequate ventilation beneath floor level with slide outs, to keep cG as low as possible ? 3 rows, 5 panels deep, are 15 total at rated 475W/panel with two 4kW/hr inverters. 7.2kW/hr goes a long way with my 2022 all electric Ford Lightning coupled on this pure solar power and a range huge for a bit through the night… your thoughts ? Thanks!

Most solar panel datasheets list the panel weight in kg (see example below). Most 300 to 450W solar panels weight between 18kg and 25kg. Although, there are flexible panels which are might lighter.

For mobile applications, I wouldn’t recommend using a Powerwall type system, but something like a Solar-Ark hybrid using one of the many 48V LFP battery options like the Simpliphi PHI series.

Thx, I thought there are new mono 1/2 cell larger commercial panel sizes 48" x 84" that recently were updated with 640-675 W/hr capacity. Are these NOT suited for mobile appls.? In addition large Lith Ion battery packs can get a lot of storage that I can apply to towing the trailer at night… how many is feasible? 12-14? Ford Lightning states 48kW/hr being necessary for a 65mph tow. Seems a bit high to me. Any opinioin on this? Thx.

The larger 550W+ panels are really only available for utility-scale system developers. You can’t buy just one or two 650W panels, you’ll need to order thousands of them.
Measure your roof area and figure out how many standard (400 to 500W) panels can fit in a landscape or portrait orientation. You might find you can get more overall kW if you use smaller panels to fill in odd areas.

@QDP I’m not sure what you are trying to achieve in regards to towing a trailer at night? Do you want to charge the Ford Lightning from the trailer-mounted off-grid system at night? Charging during daylight hours would be more efficient

Thx Svarky, Yes, tow cap/distances. I want to have as much autonomy in being able to drive substantial distances with max charging and battery capacity. Day or Night, a bug out trailer combo. My roof size is limited, 8’ x 26’ so I’d like the highest capacity array possible, along with max capacity battery packs located in pull out shelves under the trailer frame. Towing 7klbs at 65mph with the Lightning requires 48kW/hr at what amperage? One 12kW Sol Ark converter with a small gas inverter for short load conditions overkill? Thats why I’d like the highest cap. array.

Weight/roof load issue. Fewer larger panels with higher power seem better than lower power higher unit #.

@QDP, if you want the maximum solar power from your limited roof area, then you need to use the most efficient solar panels you can afford, not the largest most powerful panel. If you can fit 1 or 2 smaller more efficient panels, then you would have more total kW overall. The Sunpower Maxeon 3 panels are still the most efficient panel in the world, and also the most durable.

Agreed. I like Max3s. Sol Ark 5k and 10kW batts. Some new “Blue” panel Bifacials are supposedly coming to market now. Wait on the increased 28% eff. this year?

@QDP I have used and tested some first-generation bifacial panels, but they only increase efficiency when mounted at a 30 to 45 degree angle on a light coloured rooftop. When I mounted them flat on the roof (about 3 inch offset) they didn’t appear to have any benefit. I’d just go with the Max3’s

Good Advice, thx! Max3s it is, then add a Sol Ark 5k (overkill with 10kW Lifego batts ?) , of use the T Powerwall INSIDE horizontal (keeps my ass cozy warm, LOL!) under sofa? Advisable to mount it flat, or NOT A GOOD IDEA for ventilation? Like passive, not forced ventilation. Also, Like it indoor RV instead of under floor outside, to keep temps reasonable, but maybe too much storage for too little use. Or just go with someones full system, save some bucks?

Yeah, just go with a Sol-Ark and modular LFP battery system of your choice. You cannot use a Tesla Powerwall because it must be AC-coupled with a solar inverter to operate. Also, it cannot be mounted flat and would void the warranty

Ventilation is very important for any inverter, but the batteries just like to be at a stable temperature (not too hot and not freezing)

If using Sol-Ark, you need strings of panels with a minimum Vmp of 150V. (Min 3 x Sunpower Max3’s in series)