it's now been a few weeks since my iPhone 6 started charging extremely slow after reaching 70% battery life. I am aware of what slow trickle charging is, and the issue I am having is not it. After reaching around 70% my iPhone charges by 1% every 25/30 minutes and even seems to slow down towards the 80/90%. In fact when I tried to charge it to 100% it took me the whole day. I tried every suggestion I could find on the internet, including restarting, resetting, and even erasing all content and settings and restoring the device (not using a backup). I am starting to think the battery has an issue, but just a few weeks ago I had zero issues related to my battery. Thank you in advance
It should take 4 hours to charge iOS devices with the official supplied adapter when the device is idle or powered off. Healthy batteries should reach 80% in two hours. Then two more hours for the last 20%.
If yours plateaus sooner, it’s either due to power drain of things running while it charges or a sign that the charger or battery is out of specifications.
Using a charger with less power than the original charger might not have enough power to sustain trickle charge (ie. it trickle charge with lower W).
An other solution I found on my Android device was changing the cable. Smart chargers use dual lanes. One for charging and one for communication. If the communication is broken the charger wont be able to tell when to start or stop fast charging your phone and will "play it safe" by lowering the V.
I'm not sure if the dual line communication actually have dual lines or if it somehow switches between communication and charging, but when you buy a new cable you can choose one without or one with fast/quick-charging.