We market most of our solar torches as water resistant, and for years that meant they survived a splash test in our QC corner. A bench splash test is not the same as a Manila rainy season, as we found out in 2025.
A buyer there reported units charging strangely after heavy rain. Some wouldn't take a charge from the USB port at all, others drained overnight. When we got samples back, you could see faint corrosion on the USB pins. Water had wicked in through the rubber port flap, sat there, and slowly eaten the contacts.
The flap itself wasn't bad. The problem was that humid air plus a tiny gap means condensation forms inside even when no rain gets in directly. In a dry climate this never shows up. In a place that's 90 percent humidity for months, it absolutely does.
We changed two things. First, a deeper recessed port with a proper gasket lip, not just a flat flap. Second, we conformal-coated the little charging board so the pins and traces have a thin protective layer. That coating step adds time on the line and the operators grumbled, but it works.
We re-tested by leaving units in a sealed box with a tray of water and a heat lamp cycling on and off, our poor man's humidity chamber, for about three weeks. No corrosion this time.
Side note, the same buyer asked why we don't just make the whole thing fully sealed with wireless charging only. We tried costing it. For a torch that sells under five dollars, wireless charging triples the board price. So, recessed port and conformal coating it is. Sometimes the boring fix is the right one.
