Fake charger from "authorized reseller"?

What you think of as a "charger" is basically just a power supply adaptor which converts AC Mains power (110/220v depending where you live) into a much lower DC voltage which your iPhone can accept for charging the battery. All the intelligence and control is in your iPhone. The phone will control the charging process and how much power is put into the battery (how fast). When the phone decides the battery is fully charged it will stop charging. What this means is the gadget you purchased will either provide enough power to charge the battery, or it might not provide enough power. Either way the phone controls the process, and it doesn't really care which gadget provides the power. The first place I would be looking is the battery indicator on your iPhone. If it says the battery is 100% charged, the battery is 100% charged and it doesn't matter what kind of charger got it from low level to 100%.

If your phone battery is starting to show its age it is possible that the observed storage has degraded from original capacity. Go into Settings and scroll down to find Battery then look for Battery Health and see Apple's description in iPhone Battery and Performance - Apple Support

emmanuel_wp wrote:

I recently bought a charger for my iPhone from an "authorized reseller" but my battery life is very short when chagred with the charger in question, and thus I am suspecting I have been scammed. Is there a way to find evidence for this?

The box looks original and there is a serial numer but it's not considered valid when entered on checkcoverage.apple.com, is this the case for all chargers, or does it proove that my charger is not original apple?

That could mean that it wasn't necessarily registered with Apple as a purchase. I've rarely seen it, but my current Mac (purchased in 2015) doesn't show up as a confirmed purchase. I've still been able to get service for it from Apple and it otherwise works.

There can be a certain amount of confusion since "charger" is often used as the vernacular for a power adapter, and sometimes even for a cable. I wish there was less confusion over the language, but it is what it is.