What "Tested Before Shipment" Really Means at a Charger Factory
Most factories that say "tested before shipment" mean one thing: the light came on. I've seen that habit sink whole batches. Here's what a line should actually check — in plain order, no textbook talk.
I've walked through a fair number of charger factories, and there's one habit I keep running into. The QC guy plugs the charger in, the light comes on, the meter shows voltage, and that's it — into the box it goes.
Looks fine. Usually isn't.
The call always comes later. "Your charger is slow." "It keeps disconnecting." The factory pulls one back, plugs it in, light's on, voltage's right. Can't find a thing wrong. So where's the problem?
It's in the handshake.
A charger isn't "powered and outputting" and done. It has to talk to the phone. The phone says "I'll take 9V," the charger says "here's 9V." That conversation is the fast-charge protocol — PD, QC, PPS, and a pile of private ones. If the talk goes badly, the phone drops to 5V trickle, or connects and drops and connects again.
Here's the trap: a basic power-on check uses a dummy load. A resistor, an electronic load — something that draws power but never talks back. So the handshake step never actually happens during your test. You tested "it outputs." The customer tests "it negotiates." Two different things.
So "tested" and "tested right" are not the same sentence.
What a line should actually check
- Incoming parts (IQC). Capacitors, transformers, the power IC — don't just read the spec sheet. Batches drift. Sample the critical ones.
- Function (FCT). Does it hit 5/9/12/15/20V where it should, and hold?
- Protocol — the one everyone skips. Run it against a real protocol tester that acts like a phone. Did PD/QC/PPS actually negotiate? At the voltage and current it claims? A power-on light tells you nothing here.
- Ripple. Is the output clean? Dirty ripple quietly kills sensitive gear — earbuds, watches.
- Heat and aging. Full load for a few hours. Don't let it drift the moment it warms up.
- Protection. Over-current, over-voltage, short — does it fall back safe when things go wrong?
Steps 3 and 4 are exactly what we built our tester to do on the line: one bench unit runs the full PD/QC/PPS handshake, measures ripple, and logs each result to MES so you can trace any unit later.