A solar-powered IoT node belongs in a sealed stainless enclosure rated NEMA 4X / IP66 by the manufacturer; not UL listed, with the panel, antenna and any drain outside the box and the battery, charger and radio inside. The panel does not need to be on the enclosure at all: a small panel on a nearby pole or bracket usually shades better and angles better than one glued to the lid. What you must get right is the wall itself. Every penetration is a potential leak, and every leak eventually reaches the battery.
The environment your box actually sees
An off-grid node is usually the worst-case outdoor box: no shelter, no conditioned air, no maintenance visits. It gets rain driven by wind, sun on at least one face year-round, dust, and in coastal or roadside sites salt or de-icing spray. Winter adds snow load and, inside the box, condensation cycles as the sun heats the air by day and it cools at night.
That points to a Type 4X enclosure: hose-directed water and corrosion resistance. If the site can flood or the box can end up face-down in a ditch, step up to Type 6P. The type definitions are covered in the NEMA enclosure types guide, and the 4X-versus-6P salt-spray detail in the NEMA 4 vs 4X vs IP66 guide. Our boxes are rated by the manufacturer for the specified design and are not UL listed, so check whether your inspector requires a listing before you order.
Rating and material
Stainless steel earns its keep here. A 304 box covers most inland outdoor sites; 316L is the call near salt water, brine or chemical spray. We build both in 304 and 316L stainless wall-mount and HMI lines, and as custom one-off parts where you set the size and every cutout. If you are weighing grades, the 304 versus 316L comparison is short: chlorides decide it.
Polycarbonate and fiberglass boxes are lighter and RF-transparent, but a solar node usually wants the mechanical strength and the mounting feet of a metal box on a pole. If you choose non-metallic anyway, note that RF then passes the wall and the antenna question changes; the trade-offs are set out in the polycarbonate vs fiberglass enclosures guide.
Where the panel and battery go
Two layouts work. Panel on the enclosure lid is compact but forces the box to face the sun, which means maximum solar gain on the box and the highest internal temperature. Panel on a separate bracket wins in most installs: you point the panel south at the site's latitude tilt and put the box in whatever shade exists.
Inside, the battery is the largest item and drives the box size. Estimate the daily energy: a node averaging 50 mA at 12 V uses roughly 0.6 Ah per day, so five sunless days at a site without grid backup wants around 3 Ah usable, and double that for lead-acid depth-of-discharge. Leave room around the battery for air movement and for the charger. For the electrical side, the same layout thinking as any low-power panel applies: DIN rail for the charger and fusing, battery strapped low, terminals accessible. The sizing method is the one in the guide to sizing an electrical enclosure.
Heat is the other sizing input. A sealed small box in direct sun can run 15-20 C above ambient; the solar heat load is just another internal wattage added to the same sealed-box heat calculation. Lithium cells and most radios want to stay under about 45 C long-term, so shade the box or oversize it, and check the heat calculation before ordering.
Getting the antenna out without losing the rating
An antenna inside a stainless box will not perform; the wall blocks RF. The fix is a bulkhead feedthrough: an SMA connector through the wall, sealed with its own gasket and O-ring, coax kept short inside. Mount a patch or whip antenna on the outside wall or a short mast above it. Done with the right hardware and sealant, this keeps the rating.
Panel leads need the same discipline: a properly sized cable gland on the incoming pair, drip loop below the gland, and if you want a serviceable entry, a gland plate instead of drilled holes in the box wall. If the radio and grounding bond the metalwork, follow the enclosure grounding and bonding guide.
Size, mounting and condensation
Pick inside dimensions from the battery plus charger plus radio with 20-30% spare depth for wiring, then check the heat rise. Mount high enough that snow, splash and string trimmers stay away, with the door swings and clearances any outdoor wall-mount box needs; the siting and mounting rules are in the outdoor electrical enclosures guide and the enclosure mounting guide. Every sealed outdoor box benefits from a plan for condensation, because the daily sun cycle pumps humid air in and out unless the box is truly sealed and buffered; the rating alone cannot stop it.
What to put on the order
Work the decision into a spec before you order:
| Requirement | What to specify |
|---|---|
| Rating | NEMA 4X / IP66, manufacturer-rated; 6P if submersion is credible |
| Material | 304 stainless inland; 316L for salt or chemical sites |
| Inside size | Battery + charger + radio with 20-30% spare depth; check heat rise |
| Antenna | Bulkhead SMA feedthrough cutout, antenna outside |
| Power entry | Gland sized for the panel leads, drip loop outside |
| Mounting | Wall-mount feet or pole bracket, door swing clear |
| Extras | Gland plate if entries may change; condensation management per site |
If choosing between standard sizes and a one-off is the next step, the size finder for stainless enclosures filters every box by grade and size, and custom enclosures take your exact dimensions and cutouts from one piece, delivered in 10 business days. To work from environment and listing requirements instead, start at the enclosure selector. For the fundamentals behind the rating language, see the NEMA enclosure types guide and the IP rating chart guide.
Questions
Can a solar charge controller and lithium battery share the enclosure with the radio?
Yes, and it is the right layout. The panel, not the electronics, is the weather exposure. Put the charger, battery and radio inside the sealed box, and take the panel leads and antenna coax through sealed glands and a proper feedthrough. Watch heat: a charge controller dissipating a few watts in a small sealed box needs a size and heat check before you order.
Does the antenna have to go outside a metal enclosure?
With a stainless steel enclosure, effectively yes. The wall attenuates RF enough that an antenna inside gives short, unreliable range. Take the connection out through a bulkhead SMA feedthrough or a sealed gland and mount the antenna on the outside wall or a short mast. A correctly sealed feedthrough does not cost you the rating.
How big should the battery be for a solar IoT node?
Size for the longest stretch of overcast or polar night you expect, plus reserve. A node drawing 50 mA average needs about 1.2 Ah per day. Five sunless days means roughly 6 Ah usable, and with lead-acid chemistry you double that for depth-of-discharge. Add the charge controller and low-temperature cutoffs before you finalize the size.
Will a small solar panel keep a NEMA 4X enclosure cool?
No. The panel powers the device; it does nothing about heat. A small sealed box in direct sun can sit 15-20 C above ambient. Shade or shield the enclosure, and check the internal heat rise with the same method used for any sealed outdoor box before you commit to a size.
