Almost every solar street light datasheet says IP65. Almost every failed lamp we open in the workshop also said IP65. The rating is a useful baseline, but it describes a test, not a service life.
Where Water Actually Gets In
Not through the lens. Water enters through cable entries, battery covers and the seam between the optical chamber and the driver bay. A single continuous gasket around a complex housing is difficult to compress evenly, and a poorly compressed gasket leaks quietly for months before the electronics fail.
The better design uses separate seals per compartment, so a failure at the battery cover does not flood the driver. Threaded cable glands, rather than open grommets, close the second common path.
Why Salt Spray Matters More Than IP
IP testing uses fresh water. Coastal installations face salt, which attacks fasteners and brackets long before it reaches the electronics. A lamp can be perfectly sealed and still fall off a pole because the bracket corroded through.
| Question |
What a good answer sounds like |
| How many gaskets? |
Separate seals per compartment |
| How are cables sealed? |
Threaded glands with strain relief |
| Is the housing die-cast? |
Yes, with a machined gasket groove |
| Salt spray tested? |
Yes, with the test duration and result |
| Is there a drain path? |
Condensate managed away from the PCB |
The Condensation Problem
Sealed housings breathe. Temperature swings pull moisture in through the smallest gap and condense it on cold metal overnight. A design that ignores this ends up with a swimming pool inside the driver bay after two seasons, even though the IP test passed.
Practical mitigations include a breathable membrane vent, a desiccant sachet in the driver compartment, and a housing shape that lets condensate collect away from the board.
“The IP rating got the product into the tender. The gasket design decides whether we replace it in year two." — Maintenance engineer, coastal project
Testing Without a Laboratory
Most buyers cannot run an IP test, but they can run a useful approximation. Mount five units on a test pole, leave them through a month of weather, then open one and inspect the gasket groove, the cable gland and the driver board for moisture or corrosion. Photograph the inside before and after. If the housing is dry and the gasket has kept its shape, the design is probably sound.
What to Do Before Approving a Lamp
Ask for the sealing drawing, not just the rating. Open a sample and count the gaskets. Check the cable entry with your hand. Ask what happens to condensate. Then leave five units on a test pole for a month and open one afterwards. That is a more reliable approval process than any certificate.
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