Key takeaways
- Environmental requirements are the written limits of where a product will live: its hottest and coldest temperatures, water, dust, sunlight, motion and power source.
- A product that works on your desk can still fail in the field, because heat, cold and electrical spikes push parts outside the ranges they were chosen for.
- Write the environment into the requirements on day one, since it decides the battery, the enclosure plastic and the protection on the power input.
- Then test the prototype in the real place: a parked car in summer, a freezer overnight, repeated engine starts, or whatever your product will actually face.
Environmental requirements are the written limits of the place your product will live: the hottest and coldest temperatures it will see, the water, dust and sunlight it will face, how it will be moved or dropped, and where its power comes from. Write them down before you choose a single part, because they decide which battery, plastic and power protection the product needs.
Most first prototypes are built and tested on a workbench, at room temperature, powered from a clean USB port. That is the right place to prove a function works. It is the wrong place to prove the product will survive. This guide shows what changes between the bench and the field, how to write the environment into your requirements, and which parts it changes. Testing methods and standards are covered in our prototype testing checklist; this article is about deciding what to test against.
Your desk is not the dashboard. A product is only as reliable as the harshest place it will actually live.
Why a product that works on your desk fails in the field
Take a GPS tracker built to sit on a car dashboard. On the bench it works perfectly. In a car, three things change at once.
- Heat. In a 2018 study by researchers at Arizona State University and UC San Diego, published in the journal Temperature, cars parked in the sun on summer days in Tempe, Arizona, reached an average cabin air temperature of 116°F after one hour, and dashboard surfaces averaged 157°F.
- Battery limits. According to Battery University, consumer lithium-ion cells should be charged only between 32°F and 113°F (0°C to 45°C) and discharged between -4°F and 140°F (-20°C to 60°C). A dashboard in summer sits above the discharge limit, and heat shortens battery life even inside the range: Battery University estimates that a fully charged lithium-ion cell stored for a year at 104°F (40°C) keeps about 65% of its recoverable capacity, against 80% at 77°F (25°C).
- Cold. In winter the same cell delivers far less. Battery University notes that a battery delivering full capacity at 80°F will typically deliver only about half at 0°F (-18°C), with the exact figure depending on chemistry. Charging below freezing is worse: research on lithium plating shows it deposits metallic lithium on the anode, which causes permanent capacity loss and can grow into needle-like structures that threaten the separator.
- Vehicle power. A car’s 12V supply is not clean. A primer from Monolithic Power Systems describes worst-case cold-crank dips below 3V lasting 15 to 50 ms, and load dump surges that can exceed 100V in a 12V system when unsuppressed, taking up to 400 ms to decay.
None of this shows up on a desk. In our experience at Inventornest, one recurring cause of first-build issues is a component performing differently in the actual application from what its supplier claims. The environment is one place that gap can open.
Your desk is not the dashboard
A car accessory that passes every test on a workbench meets a different world once it is installed. Each row below changes a part choice.
| Condition | Your desk | A car dashboard |
|---|---|---|
| Temperature | Room temperature, steady all day | Dashboard surface averaged 157°F after one hour in Arizona summer sun; winter nights fall well below freezing |
| Battery charging | Charges whenever it is plugged in | Consumer Li-ion cells should not charge below 32°F or above 113°F |
| Power input | Clean USB port or bench supply | A worst-case cold crank can pull a 12V system below 3V for 15 to 50 ms; an unsuppressed load dump can exceed 100V |
| Sun and light | Indoor light | Hours of direct sun and radiant heat; side and rear glass often let more UVA through than the windshield |
| Moisture and motion | Dry and still | Road vibration and condensation from hot-to-cold swings |
Sources: Vanos et al., Temperature (2018); Battery University BU-410; Monolithic Power Systems primer on ISO 16750-2 and ISO 7637-2 transients; Almutawa et al., Photodermatology, Photoimmunology & Photomedicine (2013).
Write the environment into your requirements on day one
An environment requirement is useful only when it names a place and a number, the same rule our guide for non-technical founders on hardware product development applies to every requirement. “Rugged” or “works outdoors” cannot be designed against or tested. “Runs at 14°F, charges only at 41°F or above, survives a 157°F dashboard while parked” can. Four groups of questions cover most consumer and light commercial products:
- Temperature. The hottest place it will sit, including a shipping container or a parked car, the coldest place it must still work, and the range it will be charged in.
- Water, dust and sun. Rain, splashes, washing or immersion; dust, sand, lint or grease; hours of direct sunlight.
- Power. Battery, USB, wall outlet or vehicle supply, and what else shares that supply.
- Use and lifetime. Drops, vibration and handling, how many years it should last, and which countries it will be sold in.
The last question matters more than it looks. At Inventornest, we ask which countries or regions a client intends to sell in because those destinations may affect technical requirements and certification planning. A product designed for Florida and later shipped to Minnesota has a different coldest day.
These answers belong in the earliest technical work, alongside the core function. A product feasibility analysis is the natural place to capture them, because the environment can rule out a part, a battery chemistry or an enclosure method before any money is spent on them.
Write the environment down before you pick a part
Answer each line with a place and a number, not an adjective. “Works outdoors” cannot be tested. “Runs at 14°F and charges at 41°F or above” can.
How the environment changes the parts you choose
Each line on the environment sheet points at specific parts, and the time to choose them is early. At Inventornest, we assess a change by its value, the problem it solves and the work it invalidates. Changes are generally easier during feasibility and early design; after PCB fabrication, enclosure development or tooling, the same change can require new hardware, firmware updates, mechanical revisions and repeated testing.
The battery
At Inventornest, we select battery chemistry and capacity around power demand, required runtime, charging method, operating environment, size and replacement needs. For a product that lives somewhere hot or cold, that means:
- A cell rated for the full range, checked on the manufacturer’s datasheet for both charge and discharge temperatures, not only the capacity.
- A charging circuit that reads the cell temperature through an NTC thermistor. Charger chips built for this, such as those described in Texas Instruments’ NTC application note, stop charging below a cold threshold and above a hot one, and can reduce charge current in the warm band, so the charger does not try to charge a frozen cell.
- Capacity sized at the coldest temperature, since a battery that lasts a week in the lab may last far less in winter.
In our experience, battery optimization is often underestimated. Battery performance should be treated as a core requirement from the beginning and verified through practical testing.
The enclosure plastic
Sunlight and heat attack plastic differently from the way they attack electronics. Research on weathered ABS, one of the most common enclosure plastics, found that accelerated UV aging yellows the material and embrittles its exposed surface, cutting impact strength sharply. A hot dashboard can also soften a material whose heat rating sits below the surface temperature.
- For sun exposure, choose a grade made for outdoor use, such as ASA, which material suppliers develop for automotive exterior parts and outdoor equipment, or a UV-stabilized grade, and check its UL 746C outdoor suitability rating. An f1 rating means the material kept its key properties after 720 hours in a twin enclosed carbon-arc weatherometer or 1,000 hours in a xenon-arc unit, plus seven days of water immersion at 70°C.
- For heat, compare the material’s heat deflection temperature, the temperature at which a loaded test bar bends by a set amount under ASTM D648, with the hottest surface on your environment sheet, leaving margin.
- For prototypes, remember that a printed part may use a different material from the production part, so heat results from a printed housing do not carry over automatically. The guide to plastic part manufacturing methods covers how the process changes the part.
The power input
A product powered from a car, truck, boat or machine needs protection on its input that a USB gadget does not.
- Load dump protection, which usually starts with a transient voltage suppressor (TVS) diode sized for the vehicle’s worst-case surge and, depending on the design, further protection behind it, which keeps a spike from reaching the regulator.
- Reverse polarity protection, from a series diode or a MOSFET-based ideal-diode circuit, which means a battery connected backwards during a repair does not destroy the board.
- Ride-through for engine starts, from a regulator and hold-up capacitance that keep the product running, or restarting cleanly, through a cold crank dip.
The parts on the board need the same check. A chip rated only for 0 to 70°C is the wrong choice for a part that bakes on a dashboard all summer. Parts qualified for vehicles carry AEC-Q100 temperature grades, with Grade 1 covering -40°C to +125°C, which gives a useful benchmark when you compare datasheets.
Each environment line becomes a part choice and a test
The dashboard example traced from the requirement sheet to the bill of materials to a field test. The same path works for a garden sensor or a gym wearable.
Write the line
Where does it live, and what are the limits?
- Example
- Mounted on a dashboard. Surface heat above 150°F in summer, below freezing in winter, powered from the 12V socket
- Leaves behind
- A requirement with numbers that every part is checked against
- If you skip it
- Parts get chosen for the conditions on the bench
Choose parts against it
Does every datasheet cover that range?
- Battery
- Cell rated for the full range, with charging paused outside its charge window
- Enclosure
- UV-stable plastic with an f1 rating and a heat rating above the hottest surface
- Power input
- Protection sized for load dump and reverse polarity, with ride-through for engine starts
Test it where it lives
Does it survive the real place?
- Example tests
- A parked car in summer, a freezer overnight, repeated engine starts
- Leaves behind
- Logged results on representative hardware
- If you skip it
- Customers run the test for you, after launch
Test the prototype where it will actually live
Bench tests prove the function. Field tests prove the product. For the dashboard tracker, that means a car parked in full summer sun for an afternoon, a night in a freezer followed by a charge attempt, and a run of repeated engine starts with the tracker logging its supply voltage. A garden sensor gets a season outdoors; a gym wearable gets sweat, drops and a wash.
At Inventornest, we look beyond whether the main function works once and examine how the integrated prototype performs in realistic conditions, including thermal behavior where it applies. Supplier specifications and initial demonstrations do not reveal every issue, and formal certification testing is a separate activity where applicable. Some problems emerge only after extended or repeated use, so a single afternoon in a hot car is a start, not a validation.
The testing checklist linked above sets out the full test protocol, including temperature extremes, drops and the formal standards such as MIL-STD-810 and IEC 60529 that buyers sometimes ask about.
Common environment mistakes to avoid
Many field failures trace back to one of a handful of assumptions made early:
- Writing adjectives instead of numbers, such as “weatherproof” with no temperature, water exposure or duration attached.
- Checking only the discharge range of a battery and forgetting the narrower charging range.
- Trusting typical values on a datasheet instead of the limits across the full temperature range.
- Testing only the printed prototype and assuming the molded production material will behave the same in heat and sun.
- Adding a new market late, such as a colder region, without checking whether it changes the battery, the seals or the certification plan.
- Forgetting storage and shipping, where a product can sit in a hot truck or container longer than it will ever sit in use.
Frequently asked questions
What are environmental requirements in product design?
They are the written limits of the conditions a product must survive and work in: temperature for use, charging and storage, water and dust exposure, sunlight, vibration and drops, power quality and expected lifetime. Each one should name a place and a number so it can be designed against and tested.
How hot does a car dashboard get?
In a study of cars parked in the sun in Tempe, Arizona, dashboard surfaces averaged 157°F after one hour, with cabin air at 116°F. Shaded cars still reached a dashboard average of 118°F.
Can a lithium-ion battery be used in a car?
Yes, with the right cell and circuit. Consumer lithium-ion cells are generally limited to charging between 32°F and 113°F and discharging between -4°F and 140°F, so a car product needs a cell rated for its real range, a charger that pauses outside the charge window, and capacity sized for cold mornings.
What is load dump in a vehicle?
Load dump is a voltage surge that happens when the battery is suddenly disconnected while the alternator is delivering current to it. In a 12V system an unsuppressed surge can exceed 100V, and it is defined for testing in ISO 16750-2 and ISO 7637-2. Products that plug into vehicle power need input protection sized for it.
Which plastics are suitable for outdoor products?
Look for a UV-stabilized grade with an f1 rating under UL 746C, which shows the material passed both UV exposure and water immersion tests without significant loss of its key properties. Then check its heat deflection temperature against the hottest place on your environment sheet.
When should environmental requirements be written?
Before any parts are selected, ideally during feasibility. Changes are easier at that stage; after the PCB, enclosure or tooling exists, an environment-driven change can mean new hardware, firmware and repeated testing.
Where Inventornest fits
Clients do not need to arrive with a complete engineering specification. Our feasibility phase helps turn an initial idea into defined requirements, identify uncertainties and establish a realistic development scope, and where the product will be used and sold is part of that from the start. We consider battery performance, production component availability, manufacturability and applicable certification requirements early, rather than after the first build.
From there, our product prototyping services cover the electronics, firmware and enclosure as coordinated product design and development, then build the integrated prototype and test how it performs in realistic conditions. Inventornest brings 12+ years building hardware (since 2013), 200+ products built and 30+ industries served. To find out what your product’s real environment will demand, book a consultation and bring the hottest, coldest and dirtiest place you expect it to live.
