A bus shelter is where display hardware goes to be tested by the public. No socket, no air conditioning, nobody to wipe the glass, and an expectation that the panel is legible to someone standing in the rain at 6:40am in February. Retail signage is a controlled environment by comparison.
What follows is the conversation we have with transit authorities, media contractors and shelter fabricators before a pilot: what the hardware must survive, which numbers to demand in writing, and where these projects die. Prices are our own; every other figure is labelled as an assumption, with the method to replace it.
Why a bus shelter is the worst place for a screen
- No circuit. A shelter is a steel frame on a pavement. Mains means trenching, a wayleave, an electrician and reinstatement — usually the largest line in a retrofit budget, and the reason most upgrade programmes never start.
- Weather in both directions. Sun pushes a south-facing surface above ambient; a clear winter night drops it below freezing. The hardware has to hold colour at both ends, daily, for a decade.
- People. Impact, scratches, stickers. Glass is the wrong answer for a public asset.
A reflective e-paper panel answers the first directly: it runs from a battery, so installation needs a bracket rather than an electrician. It handles the second better than buyers expect, because there is no backlight to fight the sun. The third is an enclosure question, which is why the IP rating of the assembled unit matters more than the panel datasheet.
Four failure modes, in the order they kill projects
| # | Failure | How it shows up | What to specify |
|---|---|---|---|
| 1 | No power path | Project stalls on "who pays for the trench" | Battery runtime at your refresh rate and climate, in writing |
| 2 | Moisture ingress | Condensation behind the face after the first cold snap | IP rating of the assembled enclosure, plus the test report |
| 3 | Unreadable in the dark half of the year | Fine in June, invisible in November | Front light, its luminance, and what it draws |
| 4 | Nobody owns the content | Panels frozen on a campaign from eight months ago | Who pushes updates, over which connection, how often |
Only one of the four is about the display. Buyers spend the evaluation on resolution and gamut, then lose the project to a wayleave and a missing content owner.
The spec sheet a shelter actually needs
Published numbers for our outdoor e-paper range, so you can see the shape of the answer rather than the marketing version. Ask every supplier for the same fields in the same units.
| Field | 13″ | 31.5″ | 55″ |
|---|---|---|---|
| Operating temperature, outdoor version | −30 to 80 °C | −30 to 80 °C | −30 to 80 °C |
| Ingress rating, assembled unit | IP65 | IP65 | IP65 |
| Full refresh time | under 1 s | under 1 s | under 1 s |
| Battery, outdoor version | 15 / 15.8 Ah | 15 / 15.8 Ah | 20 / 30 Ah |
| Power drawn by a static image | none | none | none |
| Enclosure, outdoor | aluminium, 306 × 235 × 25 mm | aluminium, 767 × 462 × 69 mm | aluminium, 1280 × 765 × 40 mm |
| Connectivity | BLE / Wi-Fi | USB 2.0 / BLE / Wi-Fi | BLE / Wi-Fi |
| Night lighting | integral front light | integral front light | integral front light |
| Warranty | 3 years | 3 years | 3 years |
Two rows carry the most weight and are the most often skipped in a tender: the range of the outdoor version specifically, and the connectivity. Indoor and outdoor variants do not share a thermal spec.
Battery budget: refresh count is the wrong question
Buyers assume the refresh empties the battery. It does not, and sizing a pack around "updates per day" is how a pilot goes flat in its first winter.
- Energy per refresh. Assumption: 20 J per full-colour refresh on a 31.5″ panel, about 5.6 mWh. Illustrative, not a datasheet value. Replace it with what your supplier measures at your operating temperature, or measure it with an inline USB power meter over a hundred refreshes.
- Pack energy. 15.8 Ah at a nominal 3.7 V is roughly 58 Wh.
- Divide. 58 Wh ÷ 0.0056 Wh ≈ 10,000 full refreshes, before losses.
Ten thousand refreshes is one update every fifty minutes, day and night, for a year. No bus stop behaves like that. Radio wake on each update takes something off it, nowhere near enough to matter. The refresh is not your constraint.
What actually drains it
The front light. It is a continuous load for every hour of darkness — fifteen a day in a northern European winter. Assume 1 W; replace with the datasheet figure. That is 15 Wh a day, a quarter of the pack, before the radio and controller. December solar yield at 51° north is a fraction of June.
What does the system deliver on a December day at this latitude, with the front light on for fifteen hours — and can you show it as a measured curve rather than a calculation?
If that arrives as one optimistic number with no conditions, treat the off-grid claim as unproven and price a mains variant for winter.
Frost, condensation and IP65
Two problems hide behind "cold". The optical one is colour: a cholesteric panel keeps its image well below freezing, but saturation shifts with temperature, so the useful question is the derating curve — at what temperature does it still meet your brand colours — not the operating range.
The electrochemical one is where solar units fail quietly. Lithium must not be charged below 0 °C. A controller without a low-temperature cut-off accepts current on a frosty bright morning and plates the cell; the damage appears as lost capacity in year two, not as a fault on delivery.
Condensation is an assembly question: a sealed enclosure has nowhere for vapour to go, so if it is closed in humid air, that moisture is sealed in and finds the coldest surface on the first cold night. Ask whether final assembly happens in a dry room.
On IP65, the second digit is 5 — water projected by a nozzle, not immersion. For a shelter mounted vertically that is sufficient. Failure is almost never the panel: it is the cable gland, the antenna penetration, or the seam opened on site and closed without a new gasket. Demand the test report for the assembled unit.
Daylight is the easy part; 6pm in November is not
A reflective panel gains contrast in direct sun, the opposite of a backlit LCD, and that part of the case is real. The hard hours are dusk and flat overcast, when there is not enough ambient light to separate ink from paper. Photograph a candidate unit at 4pm, 6pm and 8pm in your city in the month you care about; it beats any luminance figure.
Two items rarely reach the business case. A reflective face is only as good as its surface; road film and salt cut contrast, so budget a cleaning interval. And planning consent: many jurisdictions distinguish illuminated from non-illuminated signage, and a panel with a front light does not fall cleanly into either class. We will not tell you it is exempt. Check at survey stage, because re-classification can add months — and if it is accepted as non-illuminated, sites previously closed to advertising open up.
Retrofit: the conversation that decides the schedule
Most projects are retrofits into frames that already exist, and the fixing pattern is where the schedule slips. Confirm with the fabricator, not only the supplier: weight of the assembled unit at each configuration, whether the 55″ fits the existing 1.2 m aperture without cutting the frame, and whether the battery is reachable without bringing the whole unit down. A panel that needs two people and a crane to swap a pack turns a fifteen-minute service into a road closure.
Cost, with the assumptions separated from the prices
Our list prices for the outdoor posters, USD, ex-works Shenzhen, with the volume tiers that apply automatically:
| Model | Panel | 1–9 units | 10–49 | 50–199 | 200+ | MOQ |
|---|---|---|---|---|---|---|
| E-Poster 13 Colour | 13.3″, 2200 × 1650 | $890 | $845.50 | $783.20 | $712.00 | 5 |
| E-Poster 31 Colour | 31.5″, 1920 × 1080 | $2,450 | $2,327.50 | $2,156.00 | $1,960.00 | 2 |
| E-Poster 55 Colour | 55″, 1920 × 1080 | $3,980 | $3,781.00 | $3,502.40 | $3,184.00 | 2 |
Now the line they replace. Assumption: a mains installation at a retrofit shelter costs USD 600–2,000 per point once trenching, a wayleave, an electrician and reinstatement are counted. Replace with a quote from your own contractor; the range is genuinely that wide and the business case turns on it. Twenty shelters at the low end is USD 12,000 of electrical work a battery unit does not need; at the high end it exceeds the hardware.
That is a wiring argument, not an energy argument. Three years of saved electricity is a rounding error at twenty units; the case is the circuit you never install.
What to put in the RFQ
Ten lines. A competent supplier answers all ten in one document; the ones who answer six are telling you something.
- Outdoor operating range, and the colour derating curve over it.
- IP rating of the assembled unit, test report and laboratory name.
- Measured energy per full refresh at 0 °C and at 30 °C.
- Front light luminance, power draw, and whether it dims on a schedule.
- Solar input rating and expected December yield at the site's latitude.
- BMS low-temperature charge cut-off: yes or no.
- How content is pushed — playlist, API, or physical media — and what happens when the network is down.
- Weight and fixing pattern of the assembled outdoor unit.
- Battery service procedure and expected pack life at your cadence.
- Warranty terms including the battery, and where service is performed.
Where our own range fits
The 13.3″ E-Poster is stop signage — timetable, route diagram, one message at a small aperture — and fits existing frames with the least carpentry. The 31.5″ E-Poster is the size most pilots settle on: readable from the pavement, one-person serviceable, available in an IP65 solar variant. The 55″ E-Poster is for interchanges and facades where the viewing distance is genuinely ten metres. All three refresh in under a second, draw nothing on a static image and carry a three-year warranty.
The full line is on the e-paper category page; a shelter-specific fixing, enclosure or your own branding on the housing is a tooling conversation, set out on the OEM page.
Send the site: latitude, mounting aperture, whether a circuit exists, content frequency, and phase-one quantity. You get a configuration, a unit price at your quantity and a ship date — and if the honest answer is that your winter needs mains power, we will say so before you order.
If any of the ten RFQ lines is still open on your side, send them over and we will answer them against a specific configuration rather than in general terms.