This is the most misdiagnosed fault in fast-charging programs. Returns come back marked “charger underperforms”, the charger meters perfectly on the bench - with the bench's cable - and the cycle repeats until someone tests the cable that was in the customer's box. USB-C cables come in two power classes, and the plug gives no visual clue which one you are holding.
The two classes
Cables are built for 3A or 5A. At USB PD's 20V ceiling that means 60W or 100W. The system enforces the limit conservatively: unless the cable identifies itself through an e-Marker chip as 5A-capable, power is capped at the 60W class. The rule is sensible - pushing 5A through a 3A cable would overheat it - but it makes the cable a silent governor on every high-wattage program.
Where it bites in real product lines
100W chargers are the obvious case: the 100W series publishes 20V/5A profiles that only an e-Marker cable can unlock. 65W chargers are the subtle case: models publishing 20V/3.25A - most of the 65W series - also need the 5A cable class for their top step, a detail buried in many a product page. Wireless kits are the safe case: the documented cable in the manufacturer's wireless line is 1 m at 3A feeding a 15W ceiling, comfortably inside the 60W class. Matching class to program is a specification exercise, set out fully in the C-to-C cable guide.
Fixing it in your program
- Write the cable class into the purchase order beside the charger: “5A, e-Marker” for every program at 65W and above.
- Read incoming cables with an e-Marker tester during inspection; the chips report their rating.
- Meter the bundle, not the components: charger plus its actual cable plus a load, at the published top profile.
- Print the cable class on the retail box. Customers mix cables at home; the box is where the expectation should be set.
The charger was never lying. The specification chain - charger, cable, device - delivers at its weakest link, which is why this site's cable section is written as specification guidance rather than a catalogue: the rating class must be chosen, quoted and verified, not assumed.
The 240W horizon
The USB PD extended power range raises the ceiling beyond 100W - up to 240W at higher voltages - and cables for that class carry their own ratings and e-Marker declarations. This catalogue's documented chargers top out at 100W, so 240W-class cables are not a stocking requirement here; the point for buyers is the principle, which scales: at every power generation, the cable class must be specified to the charger's ceiling, and the e-Marker is how the system knows. Programs that build the class check into incoming inspection now will not have to relearn it at the next wattage generation.
Length, drop and the quiet second failure
Even a correctly rated cable can under-deliver if it is long and thin: conductor resistance drops voltage along the run, and the device negotiates down to what actually arrives. This is why charging cables cluster at one to two metres and why the documented cable in this manufacturer's wireless line is one metre - short, adequately rated, matched to a 15W job. For wall-charger bundles, resist the merchandising temptation of the extra-long cable unless its conductors are specified for the drop; a 100W program deserves a cable whose length was chosen by an engineer, not by a shelf display.
The returns-desk summary
If your program ships high-wattage chargers, tape this to the returns desk: before authorising a “slow charger” return, ask which cable was used and read its class. A large share of wattage complaints are cable-class complaints wearing the charger's name. The fix upstream is specification - class in the purchase order, e-Marker checks at inspection, class printed on the box - and it costs almost nothing compared with a single container of misdiagnosed returns.
Assortment planning: how many classes to stock
Resist the urge to simplify to one cable class for everything. The 5A e-Marker cable costs more and is wasted on a 15W wireless kit; the 3A cable is correct there and wrong beside a 100W charger. Two classes, clearly labelled and never substituted at packing, is the professional assortment. The substitution point deserves emphasis: most cable-class failures happen not in purchasing but in the packing line, where a look-alike cable from the wrong bin enters the box. Bin discipline and a final e-Marker spot-check per carton are unglamorous, cheap and decisive.
How the mistake reaches the customer
Trace the failure's path once, because every link is a place to stop it. It begins in the purchase order, where “USB-C cable, 1 m” is written without a class. Purchasing buys the cheaper class in good faith. Packing pairs it with a 100W charger because the two were quoted on adjacent lines. The customer, owning a phone that can draw the charger's top profile, meets the 60W ceiling and concludes - reasonably, from everything visible - that the charger is oversold. Support swaps the charger; the replacement behaves identically, because the cable never changed. By the third contact the brand owns a reputation built entirely on an unspecified line item. Every actor in the chain behaved sensibly except the document that started it, which is why this blog returns so often to the same moral: in this category, the specification is the product, and the cable is part of the specification.
The affirmative version is just as concrete. Programs that specify class, verify e-Markers at inspection and print the pairing on the box report a characteristic review pattern: customers praising the charger for “actually delivering” its rated speed. They are praising the cable discipline without knowing its name.
One more constituency should hear the cable-class message: the gift buyer. A premium charger given with an anonymous cable is a promise halved at the moment of unwrapping, and the recipient will never know which component to blame. Retailers who bundle deliberately - class-matched cable, class printed on the box - are not upselling an accessory; they are protecting the headline product's first impression, which in this category is a measurable electrical event, not a mood.
The rule travels beyond chargers, too: any powered accessory with a detachable cable inherits the same class logic. Teach it once - to purchasing, to packing, to support - and the whole building starts hearing “which class?” in the right meetings. That question, asked early and often, is the cheapest quality system in the building.
Start with the next purchase order: add one line - the cable class - and the most common wattage complaint in the industry begins disappearing from your returns data within a season.