Short answer: order a stainless box rated NEMA 4X / IP66 by the manufacturer, keep the logger and its Li-ion pack inside, and take the antenna out through a bulkhead connector in the wall. Size the pack against the modem's 2 A transmit bursts: for a logger reporting every hour, 7 Ah runs about 39 days. The rating answers the rain; the chemistry and the box temperature answer the runtime. You can send the whole decision as one order line: 304 stainless inland, 316L near salt, a shaded wall to mount on, and a pack sized to your service interval.
The rating to ask for
Rain and hose-down take IP66. IEC 60529 awards the second digit 6 after powerful jets: a 12.5 mm nozzle at 100 L/min, aimed from 2.5 to 3 m [8-10 ft] for at least 3 minutes, must leave the electronics unharmed. The first digit 6 is dust-tight. IP67 adds 1 m [3.3 ft] of submersion for 30 minutes, a condition a wall-mounted logger almost never meets.
If the site can flood, step up to a Type 6P build, the prolonged-submersion type our custom line manufactures. Then two lines belong on your spec. In US installations, NEC 110.28 states that IP ratings are not a substitute for Enclosure Type ratings. Write 'NEMA 4X / IP66' and the inspector reads both systems at once. And the assembly holds only its weakest penetration: a gland, bulkhead connector or breather rated below IP66 sets the rating of the whole box.
Our stainless wall-mount boxes are rated NEMA 4X / IP66 by the manufacturer; not UL listed. A UL listed enclosure is one UL has evaluated to UL 50E, so a project that demands listing needs that sentence in its spec. The IP rating chart explains each digit, and the guide to NEMA 4X against IP66 maps the two systems onto each other.
What the weather does to the pack
The box keeps water out; shade is what keeps heat out. A sunlit metal enclosure runs 15-20 C above the air around it, the accepted field rule for solar gain, and dark paint or still air pushes it toward the top of that range. A 30 C afternoon therefore becomes a 45-50 C pack in your box, and that is the number that rules battery life. Published measurements of Li-ion self-discharge sit at 3-6 µA at 23 C and climb to 97 µA at 40 C, and an IEEE study of calendar aging found degradation at 60 C far harsher than at 45 C. Mount on the shaded side of the structure or under an eave and most of that rise disappears; the piece on removing heat from a small sealed IP66 enclosure covers what little is left.
Cold runs on cell-datasheet limits: discharge down to about -20 C, charge only between 0 and 45 C. A charge below freezing plates lithium metal onto the anode, and that capacity never comes back. Let a cold-soaked pack warm above 0 C before any charge current flows.
A sealed box also breathes through its gasket as day turns to night, and the moisture that enters stays in. Drop in a desiccant pack sized to the free air volume and change it at every visit; the piece on sealed boxes against vapor explains where the water comes from. If the box cycles hard every day, fit a breather vent rated IP66 by its maker and the assembly keeps its rating.
304 or 316L for the walls
304 stainless, #4 brushed, carries inland loggers: rain, sun, hose-down, dust. Choose 316L when salt is in the picture: coastal air, brine, road spray, chemical plants. The molybdenum in 316L resists the pitting and crevice attack that chloride deposits cause in 304 even at room temperature.
One temperature rules both grades. Chloride stress-corrosion cracking starts near 60 C (140 F) in 304 and 316L alike, and molybdenum does not move it. A salt-dusted box baking in the sun is the classic failure, so a coastal install takes 316L walls and a shaded spot to hang. The corrosion side is tested, not just described: NEMA 250 Table 5-1D gives Type 4X enclosures another 200 hours of salt spray beside an AISI 304 specimen. If you are quoting 304 for this duty, the buying guide for a 304 stainless NEMA 4X box walks through the decision.
Size the box around the pack
The pack sets the size more than the board does, so lay the box out from the battery outward. For a logger board, a two-cell pack and a pigtail, 12 x 10 x 6 in (305 x 254 x 152 mm) outside is a comfortable shape, with 25-30% of the volume left empty for the desiccant, the pigtail and the next revision. That size sits inside the 6 x 4 x 4 in to 60 x 36 x 16 in (H x W x D) range the stainless wall-mount line covers, and the size finder filters that whole line by grade and outside size.
Place the parts like this:
- Board on the removable mounting panel, connectors at the top.
- Pack strapped low on the back wall, as far from the modem as the box allows, held by a strap or bracket. Leave the cell unpotted so it stays cool and swaps out in a minute.
- Bulkhead SMA in the top wall, on a round, deburred hole, with the connector's O-ring doing the sealing. A stainless wall is a radio shield, so the antenna lives outside it; the piece on SMA connectors on a NEMA 4X wall walks through the cutout.
- Cable gland low on a side or rear wall, sized to the cable OD, with a drip loop hanging outside so rain cannot wick down the cable.
- Wall-mount feet on the back, and a silicone door gasket, which keeps sealing from about -60 to 200 C.
Charging moves the heat budget, because a charging pack warms and a sealed box keeps that heat in. The piece on charging a battery inside a sealed waterproof enclosure runs that arithmetic. For holders, protection boards and terminal style, the battery compartment parts list gathers the hardware. If this is your first wall-mount build, the enclosure sizing guide covers the basics, and the antenna-and-battery layout in a sealed outdoor box shows the same arrangement finished.
Feed the 2 A transmit bursts
A GSM modem pulls about 2 A during a transmit burst, which is why an application note exists on supplying GSM pulses from a 500 mA USB port: the average rating of a supply is not its burst rating. A pack has no such trouble, but its leads must be short and thick. A 1 m loop of 20 AWG drops about 66 mV at 2 A; the same loop in 22 AWG drops about 106 mV, enough to brown out a marginal modem mid-transmission.
Two cells in parallel share the burst, so a 7 Ah pack built from two 3.5 Ah 18650 cells asks 1 A of each, easy duty for the chemistry. Put the protection at the pack itself: a protection board rated above the burst, or protected cells, so a pinched lead cannot turn a sealed steel box into a fire you cannot reach. That line is worth an hour of your time before the lid closes.
Sizing the pack for a logger that reports every hour
Each input, with its source:
- 2 A transmit burst — the GSM power application note above.
- 10 s of radio time per report — an example value; replace it with your firmware's measured radio-on time.
- 24 reports per day — hourly; replace with your schedule.
- 2 mA sleep draw for the board and the sleeping modem — replace with your measured value.
- 7 Ah at 3.7 V nominal — two 3.5 Ah 18650 cells in parallel.
- 3-6 µA of self-discharge at 23 C, 97 µA at 40 C — the published cell measurements.
The rule: add the charge the radio burns to the charge the sleeping electronics burn, divide pack capacity by the daily total, then subtract what temperature steals while the logger idles.
- Radio: 2 A × 10 s = 20 A·s per report, or 5.6 mAh. Per day: 24 × 5.6 = 133 mAh.
- Sleep: 2 mA × 24 h = 48 mAh.
- Total: 133 + 48 = 181 mAh per day, an average draw of 181 ÷ 24 = 7.5 mA.
- Runtime: 7000 mAh ÷ 181 mAh/day = 38.7 days, call it 39 days.
- Self-heating: 7.5 mA × 3.7 V = 28 mW. A 12 x 10 x 6 in box carries about 0.33 m² of stainless wall, worth 0.33 × 3.7 = 1.2 W per degree C, so the electronics lift the inside by 28 mW ÷ 1.2 ≈ 0.02 C. The board never heats this box; the sun does.
- Idle losses: at 23 C, 6 µA × 8,760 h = 53 mAh a year, 0.8% of the pack. At 40 C, 97 µA × 8,760 h = 850 mAh, 12% of it.
The decision: this duty gives about 39 days on 7 Ah and about 55 days on 10 Ah, so size the pack to the service interval you can keep. Radio time moves it hard: double the radio-on time to 20 s and the daily load rises to about 315 mAh, cutting runtime to about 22 days. Past 200 mAh/day, a 7 Ah pack dies inside 35 days, so add capacity or a solar trickle. Hold the box near or below 30 C; at 40 C the pack loses 850 mAh a year to idling, five days of runtime spent on nothing.
What to put on the order
One line per decision gets the quote back right the first time. Custom work starts when you approve the drawing, and the finished box is delivered in 10 business days from that approval, anywhere in the world.
| Order line | What to write |
|---|---|
| Material | 316L stainless for salt, brine or road spray; 304, #4 brushed, inland |
| Rating | NEMA 4X / IP66, manufacturer rating; Type 6P if the site can flood |
| Outside size | 12 x 10 x 6 in (305 x 254 x 152 mm) H x W x D, or your size within the line's 6 x 4 x 4 to 60 x 36 x 16 in range |
| Cutouts | One bulkhead SMA hole in the top wall; one gland hole per cable entry, round and deburred |
| Fittings | Removable mounting panel, battery strap, wall-mount feet |
| Door gasket | Silicone, good from about -60 to 200 C |
| Entry hardware | Glands sized to the cable OD, drip loop outside |
Mark the pack position on the drawing so the strap points and the cell's distance from the modem land right the first time. The custom enclosure builder takes the grade, the size and every cutout from a single piece.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 6 in | 304 stainless | 10 x 8 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Is an IP66 enclosure waterproof enough for a logger left out in the rain?
Yes, for rain and hose jets. IEC 60529 grants the second digit 6 after powerful jets from a 12.5 mm nozzle at 100 L/min, aimed from 2.5 to 3 m for at least 3 minutes, leave the electronics unharmed. It is not an immersion rating: IP67 covers 1 m for 30 minutes, so mount above standing water or order a Type 6P build for a flood-prone site.
Can I charge the Li-ion pack inside the sealed box?
Yes, above 0 C. Cell datasheets set charging between 0 and 45 C; below freezing the charge plates lithium metal onto the anode and the capacity loss is permanent. Discharge down to about -20 C is fine. Remember a charging pack also warms the box, so add the charge watts to the heat budget before you close the lid.
How long does a 7 Ah pack run between charges?
About 39 days at one report per hour, 10 s of radio time and 2 mA of sleep: the radio burns 133 mAh a day, the sleep 48 mAh, 181 mAh in total. Fifteen-minute reporting cuts it to about 12 days, 1 mA of sleep stretches it to about 45 days, and a 10 Ah pack at the same duty lasts about 55.
Do the walls need to be 316L, or is 304 enough?
304 stainless handles inland rain, sun and hose-down. Step up to 316L near salt water or where road salt sprays the box, because its molybdenum resists the pitting that chloride deposits cause in 304 even at room temperature. Both grades risk chloride stress-corrosion cracking above about 60 C (140 F), so shade the box as well as choosing the grade.
Why must the antenna come out through the wall?
A stainless wall is a radio shield, and an antenna inside the box hears almost nothing, so the link budget collapses. Fit an IP66-rated bulkhead SMA on a round, deburred hole with its O-ring compressed, keep the inside pigtail under 0.3 m [12 in], and the enclosure rating survives the penetration along with your signal.
What stops condensation on the board?
A desiccant pack sized to the free air volume, changed at each service visit, handles the moisture that walks in through the gasket each day. A silicone door gasket keeps sealing from about -60 to 200 C. If condensation keeps coming back, fit a breather vent rated IP66 by its maker; anything with a lower rating sets the whole assembly's rating.
