The DartSolar Shell: How To Maintain It
The clear shell on top of a DartSolar is 4 mm polycarbonate — the same material family as your headlight lenses and a riot shield. It will take a hailstone, a dropped tool, and a decade of Los Angeles sun. It will not take a car wash. Here is why, how to clean it instead, how to handle the side bolts that hold it, and the one maintenance step that keeps it clear for years.
Summary: never take a vehicle with a DartSolar mounted through a car wash — brush or touchless. Brushes scratch the shell and strip its UV layer; touchless washes use high-pH presoaks that craze polycarbonate. Clean the shell by hand instead: rinse with a hose, then wipe with warm tap water, a soft microfiber towel, and at most a drop of plain, unscented dish soap, in the shade and on a cool surface. Never use citrus cleaners, glass cleaner, alcohol, bug-and-tar remover, paper towels, squeegees, or polishing compounds. Never put threadlocker or Loctite anywhere near the polycarbonate — the side bolts use Nyloc cap nuts and must stay only snug, because the shell rides in slots that let it expand and contract with temperature. Every six months, apply a clear UV protectant rated for polycarbonate. A hazy or yellowed shell is not just cosmetic: every percent of light it blocks is a percent of wattage the cells never see. Using these steps will keep your polycarbonate shell strong and clear for years.
Why Polycarbonate, and Why It Is Fussy
Polycarbonate was chosen for the shell of your solar panels because of impact strength. Pound for pound it is roughly 250 times more impact resistant than glass, and at 4 mm it weighs less than half of what an equivalent glass cover would add to your roof. It also bends instead of shattering. Fun fact: fighter jet canopies, including the F-16's, are made from polycarbonate to protect the pilot.
Even though polycarbonate is strong, flexible and does not shatter, it is a soft, amorphous plastic. Two things damage it that glass shrugs off:
Abrasion. The surface scratches easily. Fine scratches scatter light, and scattered light is light that does not reach the solar panel photovoltaic silicon cells in a straight line.
Solvents and strong alkalis. Polycarbonate is attacked by a long list of common chemicals: ammonia, alcohols, ketones, aromatic hydrocarbons, and high-pH detergents among them. The damage is not always immediate. The solvent migrates into the plastic, relieves internal stress unevenly, and the surface develops a network of micro-cracks called crazing. Once crazed, the surface is permanently hazy. There is no polish that reverses it.
Your DartSolar's shell has a factory UV-protective layer co-extruded onto its outer face. It is what keeps the polycarbonate from yellowing in the sun. It is also thin — measured in tens of microns — so anything that abrades or chemically strips the surface is removing your UV protection along with the dirt.
What a Car Wash Actually Does to It
Brush and cloth washes. The rotating brushes and cloth curtains in a friction wash carry grit from every car ahead of you. On paint with a hard clear coat, that grit leaves the swirl marks detailers complain about. On polycarbonate, it leaves deep scratches and can strip the UV layer in a single pass. The brushes are also sized for a bare roof; a mounted DartSolar is a raised ledge with edges the brush can catch, twist, and lever against its mounts.
Touchless washes. No brushes, so it seems safe. It is not. Touchless washes compensate for the missing friction with chemistry: a high-pH alkaline presoak, often sodium hydroxide-based, to saponify road film, sometimes followed by an acidic rinse to strip mineral spotting. Polycarbonate manufacturers explicitly list highly alkaline cleaners and concentrated ammonia as incompatible. Also, the presoak sits on your shell for thirty to sixty seconds, in some cases while the shell is hot from the sun, which accelerates every chemical reaction involved.
High pressure. Polycarbonate sheet itself tolerates pressure washing, manufacturers permit up to about 1,450 psi with plain water. The concern on a DartSolar is not the sheet; it is the seams, seals, and wiring harness around it. Car wash nozzles run at close range and at angles nobody chose. Skip it.
If you must use a car wash, take the DartSolar off the roof first. That is the only version of "car wash safe."
The Right Way to Clean It
This takes about five minutes and needs three things: a bucket of warm water, a clean microfiber towel, and optionally a drop of plain dish soap.
Wait for shade and a cool surface. Never clean polycarbonate in direct sun or when the shell is hot to the touch. Water and soap evaporate before you can rinse them, leaving spots and, per the manufacturers, staining. Early morning or after sunset is ideal. But if you must clean under the hot sun, just skip using any soap, just use warm water.
Rinse first. Flood the shell with a garden hose on a gentle setting to float off loose grit. Wiping a dry, dusty panel is how you grind that dust into the surface.
Wipe with warm water and a soft towel. Warm tap water, not boiling, and a clean, soft microfiber towel. Light pressure, straight passes, not circles. If there is road film the water alone does not lift, add a single drop of plain, unscented dish soap to the bucket. Fold the towel frequently so you are always wiping with a clean face.
Rinse again and dry. Rinse thoroughly so no soap film remains, then dry with a second clean microfiber towel or a soft chamois to prevent water spots.
That is the entire procedure. Anything more aggressive costs you clarity.
What Not to Use
Citrus cleaners. This is the one that surprises people, because citrus cleaners are marketed as gentle and natural. The active ingredient in most of them is d-limonene, a terpene hydrocarbon solvent extracted from orange peel. It is a solvent in the same functional class as the aromatic hydrocarbons polycarbonate manufacturers tell you never to use. It dissolves the surface, dulls it, and initiates stress cracking. Read the label on your dish soap and cleaning sprays: if it says citrus, orange, lemon, or d-limonene, keep it off the shell.
Glass cleaner. Windex, 409, Fantastik, and similar sprays contain ammonia. Ammonia is one of the most reliable ways to craze polycarbonate.
Bug-and-tar remover, adhesive remover, WD-40, gasoline. All petroleum or aromatic solvents. All will attack the surface.
Alcohol wipes and isopropyl. Fine on glass, not on the UV-protected face of polycarbonate.
Paper towels and shop towels. Both are wood pulp and mildly abrasive. Microfiber only.
Squeegees, razor blades, scrapers. Anything with an edge.
Abrasive polishes and rubbing compounds. Headlight restoration kits work by sanding off the damaged layer — which on your shell means sanding off the UV protection. If you have a scratch, contact us before you try to buff it out.
Waxes with cleaners or petroleum distillates. Most spray waxes are fine on paint and wrong on polycarbonate. If the label lists petroleum distillates, skip it.
Threadlocker, Loctite, and adhesives. Not on the bolts, not on the frame next to the shell, not anywhere near the polycarbonate. The next section explains why.
The Side Bolts: Nyloc Nuts, No Threadlocker, No Crushing
Run your hand along the side of a DartSolar and you will find the bolts that hold the polycarbonate shell to the aluminum frame. Look closely at the shell where each bolt passes through and you will see that the hole is not a hole. It is a slot.
Why the slots are there. Polycarbonate expands and contracts with temperature about three times as much as aluminum. On a shell as long as a DartSolar, the swing from a cold morning to a black-roof afternoon moves the polycarbonate several millimeters relative to the frame it is bolted to. The slots let the shell slide along the bolts as it grows and shrinks. If it cannot slide, it bows, and the ends of the slots become stress points where cracks start.
Never clamp the side bolts hard. A bolt torqued down like a wheel nut pins the shell in place and defeats the slot entirely. The side bolts should be snug: tight enough that nothing rattles, loose enough that the shell can still shift along the slot as the temperature changes. If you are reaching for a long wrench, you are already too tight. Crushing the polycarbonate under the washer also creates a permanent stress ring around the slot, which is exactly where chemical attack and crazing take hold first.
Always use Nyloc cap nuts. The side bolts ship with Nyloc cap nuts — nuts with a nylon insert that grips the threads. That insert is what keeps the nut from backing off at highway speed, so the bolt never needs to be cranked down to stay put. Nyloc nuts are meant for a single install; the nylon insert loses grip each time it is removed and re-threaded. If you ever take a side bolt out, put it back with a new Nyloc cap nut, not the old one, and never substitute a plain nut.
Never use threadlocker or Loctite anywhere near the polycarbonate. Anaerobic threadlockers — Loctite blue, red, green, and every equivalent — are methacrylate liquids. Methacrylates stress-crack polycarbonate on contact, and the damage is worst on plastic that is already under load, which is what a bolted shell is. A single drop applied to the bolt threads wicks down the shank and into the slot, and the cracks show up weeks later as a spider web spreading from the bolt hole. The same goes for super glue, epoxy, and "plastic-safe" adhesives. The Nyloc nut is the locking mechanism; nothing else belongs on those bolts.
Why Dirt Costs You Watts
A solar panel's output is roughly proportional to the light reaching the cells. A shell with a visible film of road dust, pollen, or dried mineral spots is scattering and absorbing light before it gets there. Field studies on fixed solar arrays routinely measure soiling losses of 5 to 10% in dusty climates between rains, and a vehicle-mounted panel picks up more than a rooftop does. Treat the shell the way you would treat a camera lens: a clean surface is not a cosmetic preference, it is the difference between the wattage you paid for and the wattage you get.
Haze is worse than dirt, because you cannot wash it off. A scratched or crazed shell scatters light permanently. Yellowing absorbs the blue end of the spectrum, which carries a meaningful share of the sun's energy and which the cells would otherwise convert. Both are gradual, both are avoidable, and both come from the two things this article is about: abrasive cleaning and the wrong chemicals.
Every Six Months: UV Protectant
The co-extruded UV layer on your DartSolar shell is the primary defense against yellowing, and it is good for many years on its own. A protectant coating on top of it does two things: it adds a sacrificial UV-absorbing layer so the factory layer is not doing all the work, and it makes the surface hydrophobic so dust and water spots release with a rinse instead of a wipe. Less wiping means fewer scratches.
Apply it every six months. In Los Angeles that means once around the spring equinox before the high-UV season, and once in the fall.
What to buy. Look for a clear, liquid protectant explicitly rated for polycarbonate, headlights, or clear plastics. Most products in this category are silica-based ("ceramic" or SiO2) coatings, and the good ones are rated for six to twenty-four months of outdoor exposure. Avoid anything that describes itself as a polish, restorer, or compound, those contain abrasives, and avoid anything listing petroleum distillates or solvents. Silicone-based protectant sprays also work, but most of them need reapplication every month or two rather than every six months; if you prefer that route, adjust the schedule accordingly.
How to apply. Start with a fully cleaned and dried shell, in the shade, on a cool surface. Test the product on a small corner first and give it an hour. For testing use the side of the DartSolar, the part not directly above the solar panels but rather where the side bolts are located. Then apply a thin, even coat with a clean microfiber applicator, let it flash for the time the manufacturer specifies, and level it with a second clean towel. Most coatings want twelve to twenty-four hours without rain or dew to cure. Do not stack thick coats; a thin film is the point.
Wipe a fresh coat as little as possible for the first week. After that, the shell needs nothing more than a rinse and the occasional gentle wipe until the next application.
The Short Version
Print this and keep it in the glovebox:
Never through a car wash — brush or touchless — with a DartSolar mounted
Clean in the shade, on a cool surface
Rinse with a hose, then wipe with warm water and a soft microfiber towel
At most one drop of plain, unscented dish soap
No citrus, no ammonia, no alcohol, no solvents, no paper towels, no squeegees
Dry with a clean microfiber or chamois
Side bolts snug, never tight — the shell has to slide in its slots
Nyloc cap nuts only; replace with new Nyloc nuts if removed
No threadlocker, Loctite, or adhesive anywhere near the polycarbonate
Clear polycarbonate-rated UV protectant every six months
Treat the shell like a camera lens and it will still be clear when the rest of the car is not.
