Why does my Galaxy S7 charging rate have EXTREME variation (i.e., 1 hr vs 8 hrs)?

[Android Central Question]

Here's the situation:

Samsung Galaxy S7
Original USB Charger/Plug
Other USB Chargers/Plugs

My Galaxy S7, starting at the same battery percentage, has INSANE variation in charging times. Example: sometimes a charge from 30% to 80% takes 30 minutes. Other times, it takes EIGHT HOURS.

Charger/USB plug is not the problem--tested them with my wife's phone, and her charge times don't vary or fluctuate like this.

Also tested a backup OEM charger/plug, and it did nothing.

My phone DOES seem to know whether the USB charger attached is the original, BUT adaptive fast charging almost never works.

Things I've tried:
- Factory reset
- Battery health inspection (no significant problems w/ battery, except the full capacity has of course diminished over the years)
- Different chargers
- Different electrical outlets

 

[B. Diddy]

Welcome to Android Central! It could be an issue with the phone's USB port. Blow it out with a can of compressed air, and clean the contacts with a small Q-tip dipped in rubbing alcohol.